Annex A
(normative)
Predefined Language Environment
1 [{Language-Defined Library Units} {predefined environment} This Annex
contains the specifications of library units that shall be provided by every
implementation. There are three root library units: Ada, Interfaces, and
System; other library units are children of these:]
2/2 {8652/0047} {AI95-00081-01} {AI95-00424-01}
[Standard - A.1
Ada - A.2
Assertions - 11.4.2
Asynchronous_Task_Control - D.11
Calendar - 9.6
Arithmetic - 9.6.1
Formatting - 9.6.1
Time_Zones - 9.6.1
Characters - A.3.1
Conversions - A.3.4
Handling - A.3.2
Latin_1 - A.3.3
Command_Line - A.15
Complex_Text_IO - G.1.3
Containers - A.18.1
Doubly_Linked_Lists - A.18.3
Generic_Array_Sort - A.18.16
Generic_Constrained_Array_Sort
- A.18.16
Hashed_Maps - A.18.5
Hashed_Sets - A.18.8
Indefinite_Doubly_Linked_Lists
- A.18.11
Indefinite_Hashed_Maps - A.18.12
Indefinite_Hashed_Sets - A.18.14
Indefinite_Ordered_Maps - A.18.13
Indefinite_Ordered_Sets - A.18.15
Indefinite_Vectors - A.18.10
Ordered_Maps - A.18.6
Ordered_Sets - A.18.9
Vectors - A.18.2
Decimal - F.2
Direct_IO - A.8.4
Directories - A.16
Information - A.16
Dispatching - D.2.1
EDF - D.2.6
Round_Robin - D.2.5
Dynamic_Priorities - D.5
Standard (...continued)
Ada (...continued)
Environment_Variables - A.17
Exceptions - 11.4.1
Execution_Time - D.14
Group_Budgets - D.14.2
Timers - D.14.1
Finalization - 7.6
Float_Text_IO - A.10.9
Float_Wide_Text_IO - A.11
Float_Wide_Wide_Text_IO - A.11
Integer_Text_IO - A.10.8
Integer_Wide_Text_IO - A.11
Integer_Wide_Wide_Text_IO - A.11
Interrupts - C.3.2
Names - C.3.2
IO_Exceptions - A.13
Numerics - A.5
Complex_Arrays - G.3.2
Complex_Elementary_Functions - G.1.2
Complex_Types - G.1.1
Discrete_Random - A.5.2
Elementary_Functions - A.5.1
Float_Random - A.5.2
Generic_Complex_Arrays - G.3.2
Generic_Complex_Elementary_Functions
- G.1.2
Generic_Complex_Types - G.1.1
Generic_Elementary_Functions - A.5.1
Generic_Real_Arrays - G.3.1
Real_Arrays - G.3.1
Real_Time - D.8
Timing_Events - D.15
Sequential_IO - A.8.1
Storage_IO - A.9
Streams - 13.13.1
Stream_IO - A.12.1
Standard (...continued)
Ada (...continued)
Strings - A.4.1
Bounded - A.4.4
Hash - A.4.9
Fixed - A.4.3
Hash - A.4.9
Hash - A.4.9
Maps - A.4.2
Constants - A.4.6
Unbounded - A.4.5
Hash - A.4.9
Wide_Bounded - A.4.7
Wide_Hash - A.4.7
Wide_Fixed - A.4.7
Wide_Hash - A.4.7
Wide_Hash - A.4.7
Wide_Maps - A.4.7
Wide_Constants - A.4.7
Wide_Unbounded - A.4.7
Wide_Hash - A.4.7
Wide_Wide_Bounded - A.4.8
Wide_Wide_Hash - A.4.8
Wide_Wide_Fixed - A.4.8
Wide_Wide_Hash - A.4.8
Wide_Wide_Hash - A.4.8
Wide_Wide_Maps - A.4.8
Wide_Wide_Constants - A.4.8
Wide_Wide_Unbounded - A.4.8
Wide_Wide_Hash - A.4.8
Synchronous_Task_Control - D.10
Tags - 3.9
Generic_Dispatching_Constructor - 3.9
Task_Attributes - C.7.2
Task_Identification - C.7.1
Task_Termination - C.7.3
Standard (...continued)
Ada (...continued)
Text_IO - A.10.1
Bounded_IO - A.10.11
Complex_IO - G.1.3
Editing - F.3.3
Text_Streams - A.12.2
Unbounded_IO - A.10.12
Unchecked_Conversion - 13.9
Unchecked_Deallocation - 13.11.2
Wide_Characters - A.3.1
Wide_Text_IO - A.11
Complex_IO - G.1.4
Editing - F.3.4
Text_Streams - A.12.3
Wide_Bounded_IO - A.11
Wide_Unbounded_IO - A.11
Wide_Wide_Characters - A.3.1
Wide_Wide_Text_IO - A.11
Complex_IO - G.1.5
Editing - F.3.5
Text_Streams - A.12.4
Wide_Wide_Bounded_IO - A.11
Wide_Wide_Unbounded_IO - A.11
Interfaces - B.2
C - B.3
Pointers - B.3.2
Strings - B.3.1
COBOL - B.4
Fortran - B.5
System - 13.7
Address_To_Access_Conversions - 13.7.2
Machine_Code - 13.8
RPC - E.5
Storage_Elements - 13.7.1
Storage_Pools - 13.11]
2.a Discussion: In running text, we generally leave out the "Ada."
when referring to a child of Ada.
2.b Reason: We had no strict rule for which of Ada, Interfaces, or
System should be the parent of a given library unit. However, we
have tried to place as many things as possible under Ada, except
that interfacing is a separate category, and we have tried to
place library units whose use is highly non-portable under System.
Implementation Requirements
3/2 {AI95-00434-01} The implementation shall ensure that each language-defined
subprogram is reentrant{reentrant} in the sense that concurrent calls on the
same subprogram perform as specified, so long as all parameters that could be
passed by reference denote nonoverlapping objects.
3.a Ramification: For example, simultaneous calls to Text_IO.Put will
work properly, so long as they are going to two different files.
On the other hand, simultaneous output to the same file
constitutes erroneous use of shared variables.
3.b To be honest: Here, "language defined subprogram" means a language
defined library subprogram, a subprogram declared in the visible
part of a language defined library package, an instance of a
language defined generic library subprogram, or a subprogram
declared in the visible part of an instance of a language defined
generic library package.
3.c Ramification: The rule implies that any data local to the private
part or body of the package has to be somehow protected against
simultaneous access.
Implementation Permissions
4 The implementation may restrict the replacement of language-defined
compilation units. The implementation may restrict children of
language-defined library units (other than Standard).
4.a Ramification: For example, the implementation may say, "you cannot
compile a library unit called System" or "you cannot compile a
child of package System" or "if you compile a library unit called
System, it has to be a package, and it has to contain at least the
following declarations: ...".
Wording Changes from Ada 83
4.b Many of Ada 83's language-defined library units are now children
of Ada or System. For upward compatibility, these are renamed as
root library units (see J.1).
4.c The order and lettering of the annexes has been changed.
Wording Changes from Ada 95
4.d/2 {8652/0047} {AI95-00081-01} Corrigendum: Units missing from the
list of predefined units were added.
A.1 The Package Standard
1 This clause outlines the specification of the package Standard containing
all predefined identifiers in the language. {unspecified [partial]} The
corresponding package body is not specified by the language.
2 The operators that are predefined for the types declared in the package
Standard are given in comments since they are implicitly declared.
{italics (pseudo-names of anonymous types)} Italics are used for pseudo-names
of anonymous types (such as root_real) and for undefined information (such as
implementation-defined).
2.a Ramification: All of the predefined operators are of convention
Intrinsic.
Static Semantics
3 The library package Standard has the following declaration:
3.a Implementation defined: The names and characteristics of the
numeric subtypes declared in the visible part of package Standard.
4 package Standard is
pragma Pure(Standard);
5 type Boolean is (False, True);
6 -- The predefined relational operators for this type are as follows:
7/1 {8652/0028} {AI95-00145-01}
-- function "=" (Left, Right : Boolean'Base) return Boolean;
-- function "/=" (Left, Right : Boolean'Base) return Boolean;
-- function "<" (Left, Right : Boolean'Base) return Boolean;
-- function "<=" (Left, Right : Boolean'Base) return Boolean;
-- function ">" (Left, Right : Boolean'Base) return Boolean;
-- function ">=" (Left, Right : Boolean'Base) return Boolean;
8 -- The predefined logical operators and the predefined logical
-- negation operator are as follows:
9/1 {8652/0028} {AI95-00145-01}
-- function "and" (Left, Right : Boolean'Base) return Boolean'Base;
-- function "or" (Left, Right : Boolean'Base) return Boolean'Base;
-- function "xor" (Left, Right : Boolean'Base) return Boolean'Base;
10/1 {8652/0028} {AI95-00145-01}
-- function "not" (Right : Boolean'Base) return Boolean'Base;
11/2 {AI95-00434-01} -- The integer type root_integer and the
-- corresponding universal type universal_integer are predefined.
12 type Integer is range implementation-defined;
13 subtype Natural is Integer range 0 .. Integer'Last;
subtype Positive is Integer range 1 .. Integer'Last;
14 -- The predefined operators for type Integer are as follows:
15 -- function "=" (Left, Right : Integer'Base) return Boolean;
-- function "/=" (Left, Right : Integer'Base) return Boolean;
-- function "<" (Left, Right : Integer'Base) return Boolean;
-- function "<=" (Left, Right : Integer'Base) return Boolean;
-- function ">" (Left, Right : Integer'Base) return Boolean;
-- function ">=" (Left, Right : Integer'Base) return Boolean;
16 -- function "+" (Right : Integer'Base) return Integer'Base;
-- function "-" (Right : Integer'Base) return Integer'Base;
-- function "abs" (Right : Integer'Base) return Integer'Base;
17 -- function "+" (Left, Right : Integer'Base) return Integer'Base;
-- function "-" (Left, Right : Integer'Base) return Integer'Base;
-- function "*" (Left, Right : Integer'Base) return Integer'Base;
-- function "/" (Left, Right : Integer'Base) return Integer'Base;
-- function "rem" (Left, Right : Integer'Base) return Integer'Base;
-- function "mod" (Left, Right : Integer'Base) return Integer'Base;
18 -- function "**" (Left : Integer'Base; Right : Natural)
-- return Integer'Base;
19 -- The specification of each operator for the type
-- root_integer, or for any additional predefined integer
-- type, is obtained by replacing Integer by the name of the type
-- in the specification of the corresponding operator of the type
-- Integer. The right operand of the exponentiation operator
-- remains as subtype Natural.
20/2 {AI95-00434-01} -- The floating point type root_real and the
-- corresponding universal type universal_real are predefined.
21 type Float is digits implementation-defined;
22 -- The predefined operators for this type are as follows:
23 -- function "=" (Left, Right : Float) return Boolean;
-- function "/=" (Left, Right : Float) return Boolean;
-- function "<" (Left, Right : Float) return Boolean;
-- function "<=" (Left, Right : Float) return Boolean;
-- function ">" (Left, Right : Float) return Boolean;
-- function ">=" (Left, Right : Float) return Boolean;
24 -- function "+" (Right : Float) return Float;
-- function "-" (Right : Float) return Float;
-- function "abs" (Right : Float) return Float;
25 -- function "+" (Left, Right : Float) return Float;
-- function "-" (Left, Right : Float) return Float;
-- function "*" (Left, Right : Float) return Float;
-- function "/" (Left, Right : Float) return Float;
26 -- function "**" (Left : Float; Right : Integer'Base) return Float;
27 -- The specification of each operator for the type root_real, or for
-- any additional predefined floating point type, is obtained by
-- replacing Float by the name of the type in the specification of the
-- corresponding operator of the type Float.
28 -- In addition, the following operators are predefined for the root
-- numeric types:
29 function "*" (Left : root_integer; Right : root_real)
return root_real;
30 function "*" (Left : root_real; Right : root_integer)
return root_real;
31 function "/" (Left : root_real; Right : root_integer)
return root_real;
32 -- The type universal_fixed is predefined.
-- The only multiplying operators defined between
-- fixed point types are
33 function "*" (Left : universal_fixed; Right : universal_fixed)
return universal_fixed;
34 function "/" (Left : universal_fixed; Right : universal_fixed)
return universal_fixed;
34.1/2 {AI95-00230-01} -- The type universal_access is predefined.
-- The following equality operators are predefined:
34.2/2 {AI95-00230-01}
function "=" (Left, Right: universal_access) return Boolean;
function "/=" (Left, Right: universal_access) return Boolean;
35/2 {AI95-00415-01}
-- The declaration of type Character is based on the standard ISO 8859-1 character set.
-- There are no character literals corresponding to the positions for control characters.
-- They are indicated in italics in this definition. See 3.5.2.
type Character is
(nul, soh, stx, etx, eot, enq, ack,
bel, --0 (16#00#) .. 7 (16#07#)
bs, ht, lf, vt, ff, cr, so,
si, --8 (16#08#) .. 15 (16#0F#)
dle, dc1, dc2, dc3, dc4, nak, syn,
etb, --16 (16#10#) .. 23 (16#17#)
can, em, sub, esc, fs, gs, rs,
us, --24 (16#18#) .. 31 (16#1F#)
' ', '!', '"', '#', '$', '%', '&',
''', --32 (16#20#) .. 39 (16#27#)
'(', ')', '*', '+', ',', '-', '.',
'/', --40 (16#28#) .. 47 (16#2F#)
'0', '1', '2', '3', '4', '5', '6',
'7', --48 (16#30#) .. 55 (16#37#)
'8', '9', ':', ';', '<', '=', '>',
'?', --56 (16#38#) .. 63 (16#3F#)
'@', 'A', 'B', 'C', 'D', 'E', 'F',
'G', --64 (16#40#) .. 71 (16#47#)
'H', 'I', 'J', 'K', 'L', 'M', 'N',
'O', --72 (16#48#) .. 79 (16#4F#)
'P', 'Q', 'R', 'S', 'T', 'U', 'V',
'W', --80 (16#50#) .. 87 (16#57#)
'X', 'Y', 'Z', '[', '\', ']', '^',
'_', --88 (16#58#) .. 95 (16#5F#)
'`', 'a', 'b', 'c', 'd', 'e', 'f',
'g', --96 (16#60#) .. 103 (16#67#)
'h', 'i', 'j', 'k', 'l', 'm', 'n',
'o', --104 (16#68#) .. 111 (16#6F#)
'p', 'q', 'r', 's', 't', 'u', 'v',
'w', --112 (16#70#) .. 119 (16#77#)
'x', 'y', 'z', '{', '|', '}', '~',
del, --120 (16#78#) .. 127 (16#7F#)
reserved_128, reserved_129, bph, nbh,
--128 (16#80#) .. 131 (16#83#)
reserved_132, nel, ssa, esa,
--132 (16#84#) .. 135 (16#87#)
hts, htj, vts, pld, plu, ri, ss2,
ss3, --136 (16#88#) .. 143 (16#8F#)
dcs, pu1, pu2, sts, cch, mw, spa,
epa, --144 (16#90#) .. 151 (16#97#)
sos, reserved_153, sci, csi,
--152 (16#98#) .. 155 (16#9B#)
st, osc, pm, apc,
--156 (16#9C#) .. 159 (16#9F#)
' ', '¡', '¢', '£', '¤', '¥', '¦',
'§', --160 (16#A0#) .. 167 (16#A7#)
'¨', '©', 'ª', '«', '¬', '', '®',
'¯', --168 (16#A8#) .. 175 (16#AF#)
'°', '±', '²', '³', '´', 'µ', '¶',
'·', --176 (16#B0#) .. 183 (16#B7#)
'¸', '¹', 'º', '»', '¼', '½', '¾',
'¿', --184 (16#B8#) .. 191 (16#BF#)
'À', 'Á', 'Â', 'Ã', 'Ä', 'Å', 'Æ',
'Ç', --192 (16#C0#) .. 199 (16#C7#)
'È', 'É', 'Ê', 'Ë', 'Ì', 'Í', 'Î',
'Ï', --200 (16#C8#) .. 207 (16#CF#)
'Ð', 'Ñ', 'Ò', 'Ó', 'Ô', 'Õ', 'Ö',
'×', --208 (16#D0#) .. 215 (16#D7#)
'Ø', 'Ù', 'Ú', 'Û', 'Ü', 'Ý', 'Þ',
'ß', --216 (16#D8#) .. 223 (16#DF#)
'à', 'á', 'â', 'ã', 'ä', 'å', 'æ',
'ç', --224 (16#E0#) .. 231 (16#E7#)
'è', 'é', 'ê', 'ë', 'ì', 'í', 'î',
'ï', --232 (16#E8#) .. 239 (16#EF#)
'ð', 'ñ', 'ò', 'ó', 'ô', 'õ', 'ö',
'÷', --240 (16#F0#) .. 247 (16#F7#)
'ø', 'ù', 'ú', 'û', 'ü', 'ý', 'þ',
'ÿ');--248 (16#F8#) .. 255 (16#FF#)
36 -- The predefined operators for the type Character are the same as for
-- any enumeration type.
36.1/2 {AI95-00395-01}
-- The declaration of type Wide_Character is based on the standard ISO/IEC 10646:2003 BMP character
-- set. The first 256 positions have the same contents as type Character. See 3.5.2
.
type Wide_Character is (nul, soh ... Hex_0000FFFE, Hex_0000FFFF);
36.2/2 {AI95-00285-01} {AI95-00395-01}
-- The declaration of type Wide_Wide_Character is based on the full
-- ISO/IEC 10646:2003 character set. The first 65536 positions have the
-- same contents as type Wide_Character. See 3.5.2.
type Wide_Wide_Character
is (nul, soh ... Hex_7FFFFFFE, Hex_7FFFFFFF);
for Wide_Wide_Character'Size use 32;
36.3/2 package ASCII is ... end ASCII; --Obsolescent; see J.5
{ASCII (package physically nested within the declaration of Standard)
}
37 -- Predefined string types:
type String is array(Positive range <>) of Character;
pragma Pack(String);
38 -- The predefined operators for this type are as follows:
39 -- function "=" (Left, Right: String) return Boolean;
-- function "/=" (Left, Right: String) return Boolean;
-- function "<" (Left, Right: String) return Boolean;
-- function "<=" (Left, Right: String) return Boolean;
-- function ">" (Left, Right: String) return Boolean;
-- function ">=" (Left, Right: String) return Boolean;
40 -- function "&" (Left: String; Right: String) return String;
-- function "&" (Left: Character; Right: String) return String;
-- function "&" (Left: String; Right: Character) return String;
-- function "&" (Left: Character; Right: Character) return String;
41 type Wide_String is array(Positive range <>) of Wide_Character;
pragma Pack(Wide_String);
42 -- The predefined operators for this type correspond to those for String.
42.1/2 {AI95-00285-01} type Wide_Wide_String is array (Positive range <>)
of Wide_Wide_Character;
pragma Pack (Wide_Wide_String);
42.2/2 {AI95-00285-01}
-- The predefined operators for this type correspond to those for String.
43 type Duration
is delta implementation-defined range implementation-defined;
44 -- The predefined operators for the type Duration are the same as for
-- any fixed point type.
45 -- The predefined exceptions:
46 Constraint_Error: exception;
Program_Error : exception;
Storage_Error : exception;
Tasking_Error : exception;
47 end Standard;
48 Standard has no private part.
48.a Reason: This is important for portability. All library packages
are children of Standard, and if Standard had a private part then
it would be visible to all of them.
49/2 {AI95-00285-01} In each of the types Character, Wide_Character, and
Wide_Wide_Character, the character literals for the space character (position
32) and the non-breaking space character (position 160) correspond to
different values. Unless indicated otherwise, each occurrence of the character
literal ' ' in this International Standard refers to the space character.
Similarly, the character literals for hyphen (position 45) and soft hyphen
(position 173) correspond to different values. Unless indicated otherwise,
each occurrence of the character literal '-' in this International Standard
refers to the hyphen character.
Dynamic Semantics
50 {elaboration (package_body of Standard) [partial]} Elaboration of the body
of Standard has no effect.
50.a Discussion: Note that the language does not define where this body
appears in the environment declarative_part - see 10, "
Program Structure and Compilation Issues".
Implementation Permissions
51 An implementation may provide additional predefined integer types and
additional predefined floating point types. Not all of these types need have
names.
51.a To be honest: An implementation may add representation items to
package Standard, for example to specify the internal codes of
type Boolean, or the Small of type Duration.
Implementation Advice
52 If an implementation provides additional named predefined integer types,
then the names should end with "Integer" as in "Long_Integer". If an
implementation provides additional named predefined floating point types, then
the names should end with "Float" as in "Long_Float".
52.a/2 Implementation Advice: If an implementation provides additional
named predefined integer types, then the names should end with "
Integer". If an implementation provides additional named
predefined floating point types, then the names should end with
"Float".
NOTES
53 1 Certain aspects of the predefined entities cannot be completely
described in the language itself. For example, although the
enumeration type Boolean can be written showing the two enumeration
literals False and True, the short-circuit control forms cannot be
expressed in the language.
54 2 As explained in 8.1, "Declarative Region" and 10.1.4, "
The Compilation Process", the declarative region of the package
Standard encloses every library unit and consequently the main
subprogram; the declaration of every library unit is assumed to occur
within this declarative region. Library_items are assumed to be
ordered in such a way that there are no forward semantic dependences.
However, as explained in 8.3, "Visibility", the only library units
that are visible within a given compilation unit are the library units
named by all with_clauses that apply to the given unit, and moreover,
within the declarative region of a given library unit, that library
unit itself.
55 3 If all block_statements of a program are named, then the name of
each program unit can always be written as an expanded name starting
with Standard (unless Standard is itself hidden). The name of a
library unit cannot be a homograph of a name (such as Integer) that is
already declared in Standard.
56 4 The exception Standard.Numeric_Error is defined in J.6.
56.a Discussion: The declaration of Natural needs to appear between the
declaration of Integer and the (implicit) declaration of the "**"
operator for Integer, because a formal parameter of "**" is of
subtype Natural. This would be impossible in normal code, because
the implicit declarations for a type occur immediately after the
type declaration, with no possibility of intervening explicit
declarations. But we're in Standard, and Standard is somewhat
magic anyway.
56.b Using Natural as the subtype of the formal of "**" seems natural;
it would be silly to have a textual rule about Constraint_Error
being raised when there is a perfectly good subtype that means
just that. Furthermore, by not using Integer for that formal, it
helps remind the reader that the exponent remains Natural even
when the left operand is replaced with the derivative of Integer.
It doesn't logically imply that, but it's still useful as a
reminder.
56.c In any case, declaring these general-purpose subtypes of Integer
close to Integer seems more readable than declaring them much
later.
Extensions to Ada 83
56.d {extensions to Ada 83} Package Standard is declared to be pure.
56.e Discussion: The introduction of the types Wide_Character and
Wide_String is not an Ada 95 extension to Ada 83, since ISO WG9
has approved these as an authorized extension of the original Ada
83 standard that is part of that standard.
Wording Changes from Ada 83
56.f Numeric_Error is made obsolescent.
56.g The declarations of Natural and Positive are moved to just after
the declaration of Integer, so that "**" can refer to Natural
without a forward reference. There's no real need to move
Positive, too - it just came along for the ride.
Extensions to Ada 95
56.h/2 {AI95-00285-01} {extensions to Ada 95} Types Wide_Wide_Character
and Wide_Wide_String are new.
56.i/2 Discussion: The inconsistencies associated with these types are
documented in 3.5.2 and 3.6.3.
56.j/2 {AI95-00230-01} Type universal_access and the equality operations
for it are new.
Wording Changes from Ada 95
56.k/2 {8652/0028} {AI95-00145-01} Corrigendum: Corrected the parameter
type for the Boolean operators declared in Standard..
A.2 The Package Ada
Static Semantics
1 The following language-defined library package exists:
2 package Ada is
pragma Pure(Ada);
end Ada;
3 Ada serves as the parent of most of the other language-defined library
units; its declaration is empty (except for the pragma Pure).
Legality Rules
4 In the standard mode, it is illegal to compile a child of package Ada.
4.a Reason: The intention is that mentioning, say, Ada.Text_IO in a
with_clause is guaranteed (at least in the standard mode) to refer
to the standard version of Ada.Text_IO. The user can compile a
root library unit Text_IO that has no relation to the standard
version of Text_IO.
4.b Ramification: Note that Ada can have non-language-defined
grandchildren, assuming the implementation allows it. Also,
packages System and Interfaces can have children, assuming the
implementation allows it.
4.c Implementation Note: An implementation will typically support a
nonstandard mode in which compiling the language defined library
units is allowed. Whether or not this mode is made available to
users is up to the implementer.
4.d An implementation could theoretically have private children of
Ada, since that would be semantically neutral. However, a
programmer cannot compile such a library unit.
Extensions to Ada 83
4.e {extensions to Ada 83} This clause is new to Ada 95.
A.3 Character Handling
1/2 {AI95-00285-01} This clause presents the packages related to character
processing: an empty pure package Characters and child packages
Characters.Handling and Characters.Latin_1. The package Characters.Handling
provides classification and conversion functions for Character data, and some
simple functions for dealing with Wide_Character and Wide_Wide_Character data.
The child package Characters.Latin_1 declares a set of constants initialized
to values of type Character.
Extensions to Ada 83
1.a {extensions to Ada 83} This clause is new to Ada 95.
Wording Changes from Ada 95
1.b/2 {AI95-00285-01} Included Wide_Wide_Character in this description;
the individual changes are documented as extensions as needed.
A.3.1 The Packages Characters, Wide_Characters, and Wide_Wide_Characters
Static Semantics
1 The library package Characters has the following declaration:
2 package Ada.Characters is
pragma Pure(Characters);
end Ada.Characters;
3/2 {AI95-00395-01} The library package Wide_Characters has the following
declaration:
4/2 package Ada.Wide_Characters is
pragma Pure(Wide_Characters);
end Ada.Wide_Characters;
5/2 {AI95-00395-01} The library package Wide_Wide_Characters has the following
declaration:
6/2 package Ada.Wide_Wide_Characters is
pragma Pure(Wide_Wide_Characters);
end Ada.Wide_Wide_Characters;
Implementation Advice
7/2 {AI95-00395-01} If an implementation chooses to provide
implementation-defined operations on Wide_Character or Wide_String (such as
case mapping, classification, collating and sorting, etc.) it should do so by
providing child units of Wide_Characters. Similarly if it chooses to provide
implementation-defined operations on Wide_Wide_Character or Wide_Wide_String
it should do so by providing child units of Wide_Wide_Characters.
7.a/2 Implementation Advice: Implementation-defined operations on
Wide_Character, Wide_String, Wide_Wide_Character, and
Wide_Wide_String should be child units of Wide_Characters or
Wide_Wide_Characters.
Extensions to Ada 95
7.b/2 {AI95-00395-01} {extensions to Ada 95} The packages
Wide_Characters and Wide_Wide_Characters are new.
A.3.2 The Package Characters.Handling
Static Semantics
1 The library package Characters.Handling has the following declaration:
2/2 {AI95-00362-01} {AI95-00395-01} with Ada.Characters.Conversions;
package Ada.Characters.Handling is
pragma Pure(Handling);
3 --Character classification functions
4 function Is_Control (Item : in Character) return Boolean;
function Is_Graphic (Item : in Character) return Boolean;
function Is_Letter (Item : in Character) return Boolean;
function Is_Lower (Item : in Character) return Boolean;
function Is_Upper (Item : in Character) return Boolean;
function Is_Basic (Item : in Character) return Boolean;
function Is_Digit (Item : in Character) return Boolean;
function Is_Decimal_Digit (Item : in Character) return Boolean
renames Is_Digit;
function Is_Hexadecimal_Digit (Item : in Character) return Boolean;
function Is_Alphanumeric (Item : in Character) return Boolean;
function Is_Special (Item : in Character) return Boolean;
5 --Conversion functions for Character and String
6 function To_Lower (Item : in Character) return Character;
function To_Upper (Item : in Character) return Character;
function To_Basic (Item : in Character) return Character;
7 function To_Lower (Item : in String) return String;
function To_Upper (Item : in String) return String;
function To_Basic (Item : in String) return String;
8 --Classifications of and conversions between Character and ISO 646
9 subtype ISO_646 is
Character range Character'Val(0) .. Character'Val(127);
10 function Is_ISO_646 (Item : in Character) return Boolean;
function Is_ISO_646 (Item : in String) return Boolean;
11 function To_ISO_646 (Item : in Character;
Substitute : in ISO_646 := ' ')
return ISO_646;
12 function To_ISO_646 (Item : in String;
Substitute : in ISO_646 := ' ')
return String;
13/2 {AI95-00285-01} {AI95-00395-01}
-- The functions Is_Character, Is_String, To_Character, To_String, To_Wide_Character,
-- and To_Wide_String are obsolescent; see J.14.
Paragraphs 14 through 18 were deleted.
19 end Ada.Characters.Handling;
19.a/2 Discussion: {AI95-00395-01} The with_clause for
Ada.Characters.Conversions is needed for the definition of the
obsolescent functions (see J.14). It would be odd to put this
clause into J.14 as it was not present in Ada 95, and
with_clauses are semantically neutral to clients anyway.
20 In the description below for each function that returns a Boolean result,
the effect is described in terms of the conditions under which the value True
is returned. If these conditions are not met, then the function returns False.
21 Each of the following classification functions has a formal Character
parameter, Item, and returns a Boolean result.
22 {control character (a category of Character)} Is_Control
True if Item is a control character. A control character is a
character whose position is in one of the ranges 0..31 or
127..159.
23 {graphic character (a category of Character)} Is_Graphic
True if Item is a graphic character. A graphic character is a
character whose position is in one of the ranges 32..126 or
160..255.
24 {letter (a category of Character)} Is_Letter
True if Item is a letter. A letter is a character that is in
one of the ranges 'A'..'Z' or 'a'..'z', or whose position is
in one of the ranges 192..214, 216..246, or 248..255.
25 {lower-case letter (a category of Character)} Is_Lower
True if Item is a lower-case letter. A lower-case letter is a
character that is in the range 'a'..'z', or whose position is
in one of the ranges 223..246 or 248..255.
26 {upper-case letter (a category of Character)} Is_Upper
True if Item is an upper-case letter. An upper-case letter is
a character that is in the range 'A'..'Z' or whose position is
in one of the ranges 192..214 or 216.. 222.
27 {basic letter (a category of Character)} Is_Basic
True if Item is a basic letter. A basic letter is a character
that is in one of the ranges 'A'..'Z' and 'a'..'z', or that is
one of the following: 'Æ', 'æ', 'Ð', 'ð', 'Þ', 'þ', or 'ß'.
28 {decimal digit (a category of Character)} Is_Digit
True if Item is a decimal digit. A decimal digit is a
character in the range '0'..'9'.
29 Is_Decimal_Digit
A renaming of Is_Digit.
30 {hexadecimal digit (a category of Character)} Is_Hexadecimal_Digit
True if Item is a hexadecimal digit. A hexadecimal digit is a
character that is either a decimal digit or that is in one of
the ranges 'A' .. 'F' or 'a' .. 'f'.
31 {alphanumeric character (a category of Character)} Is_Alphanumeric
True if Item is an alphanumeric character. An alphanumeric
character is a character that is either a letter or a decimal
digit.
32 {special graphic character (a category of Character)} Is_Special
True if Item is a special graphic character. A special graphic
character is a graphic character that is not alphanumeric.
33 Each of the names To_Lower, To_Upper, and To_Basic refers to two
functions: one that converts from Character to Character, and the other that
converts from String to String. The result of each Character-to-Character
function is described below, in terms of the conversion applied to Item, its
formal Character parameter. The result of each String-to-String conversion is
obtained by applying to each element of the function's String parameter the
corresponding Character-to-Character conversion; the result is the null String
if the value of the formal parameter is the null String. The lower bound of
the result String is 1.
34 To_Lower Returns the corresponding lower-case value for Item if
Is_Upper(Item), and returns Item otherwise.
35 To_Upper Returns the corresponding upper-case value for Item if
Is_Lower(Item) and Item has an upper-case form, and returns
Item otherwise. The lower case letters 'ß' and 'ÿ' do not have
upper case forms.
36 To_Basic Returns the letter corresponding to Item but with no
diacritical mark, if Item is a letter but not a basic letter;
returns Item otherwise.
37 The following set of functions test for membership in the ISO 646
character range, or convert between ISO 646 and Character.
38 Is_ISO_646 The function whose formal parameter, Item, is of type
Character returns True if Item is in the subtype ISO_646.
39 Is_ISO_646 The function whose formal parameter, Item, is of type String
returns True if Is_ISO_646(Item(I)) is True for each I in
Item'Range.
40 To_ISO_646 The function whose first formal parameter, Item, is of type
Character returns Item if Is_ISO_646(Item), and returns the
Substitute ISO_646 character otherwise.
41 To_ISO_646 The function whose first formal parameter, Item, is of type
String returns the String whose Range is 1..Item'Length and
each of whose elements is given by To_ISO_646 of the
corresponding element in Item.
Paragraphs 42 through 48 were deleted.
Implementation Advice
49/2 This paragraph was deleted.{AI95-00285-01}
NOTES
50 5 A basic letter is a letter without a diacritical mark.
51 6 Except for the hexadecimal digits, basic letters, and ISO_646
characters, the categories identified in the classification functions
form a strict hierarchy:
52 - Control characters
53 - Graphic characters
54 - Alphanumeric characters
55 - Letters
56 - Upper-case letters
57 - Lower-case letters
58 - Decimal digits
59 - Special graphic characters
59.a Ramification: Thus each Character value is either a control
character or a graphic character but not both; each graphic
character is either an alphanumeric or special graphic but not
both; each alphanumeric is either a letter or decimal digit but
not both; each letter is either upper case or lower case but not
both.
Extensions to Ada 95
59.b/2 {AI95-00362-01} {extensions to Ada 95} Characters.Handling is now
Pure, so it can be used in pure units.
Wording Changes from Ada 95
59.c/2 {AI95-00285-01} {AI95-00395-01} The conversion functions are made
obsolescent; a more complete set is available in
Characters.Conversions - see A.3.4.
59.d/2 {AI95-00285-01} We no longer talk about localized character sets;
these are a non-standard mode, which is none of our business.
A.3.3 The Package Characters.Latin_1
1 The package Characters.Latin_1 declares constants for characters in ISO
8859-1.
1.a Reason: The constants for the ISO 646 characters could have been
declared as renamings of objects declared in package ASCII, as
opposed to explicit constants. The main reason for explicit
constants was for consistency of style with the upper-half
constants, and to avoid emphasizing the package ASCII.
Static Semantics
2 The library package Characters.Latin_1 has the following declaration:
3 package Ada.Characters.Latin_1 is
pragma Pure(Latin_1);
4 -- Control characters:{control character (a category of Character)
[partial]}
5 NUL : constant Character := Character'Val(0);
SOH : constant Character := Character'Val(1);
STX : constant Character := Character'Val(2);
ETX : constant Character := Character'Val(3);
EOT : constant Character := Character'Val(4);
ENQ : constant Character := Character'Val(5);
ACK : constant Character := Character'Val(6);
BEL : constant Character := Character'Val(7);
BS : constant Character := Character'Val(8);
HT : constant Character := Character'Val(9);
LF : constant Character := Character'Val(10);
VT : constant Character := Character'Val(11);
FF : constant Character := Character'Val(12);
CR : constant Character := Character'Val(13);
SO : constant Character := Character'Val(14);
SI : constant Character := Character'Val(15);
6 DLE : constant Character := Character'Val(16);
DC1 : constant Character := Character'Val(17);
DC2 : constant Character := Character'Val(18);
DC3 : constant Character := Character'Val(19);
DC4 : constant Character := Character'Val(20);
NAK : constant Character := Character'Val(21);
SYN : constant Character := Character'Val(22);
ETB : constant Character := Character'Val(23);
CAN : constant Character := Character'Val(24);
EM : constant Character := Character'Val(25);
SUB : constant Character := Character'Val(26);
ESC : constant Character := Character'Val(27);
FS : constant Character := Character'Val(28);
GS : constant Character := Character'Val(29);
RS : constant Character := Character'Val(30);
US : constant Character := Character'Val(31);
7 -- ISO 646 graphic characters:
8 Space
: constant Character := ' '; -- Character'Val(32)
Exclamation
: constant Character := '!'; -- Character'Val(33)
Quotation
: constant Character := '"'; -- Character'Val(34)
Number_Sign
: constant Character := '#'; -- Character'Val(35)
Dollar_Sign
: constant Character := '$'; -- Character'Val(36)
Percent_Sign
: constant Character := '%'; -- Character'Val(37)
Ampersand
: constant Character := '&'; -- Character'Val(38)
Apostrophe
: constant Character := '''; -- Character'Val(39)
Left_Parenthesis
: constant Character := '('; -- Character'Val(40)
Right_Parenthesis
: constant Character := ')'; -- Character'Val(41)
Asterisk
: constant Character := '*'; -- Character'Val(42)
Plus_Sign
: constant Character := '+'; -- Character'Val(43)
Comma
: constant Character := ','; -- Character'Val(44)
Hyphen
: constant Character := '-'; -- Character'Val(45)
Minus_Sign : Character renames Hyphen;
Full_Stop
: constant Character := '.'; -- Character'Val(46)
Solidus
: constant Character := '/'; -- Character'Val(47)
9 -- Decimal digits '0' though '9' are at positions 48 through 57
10 Colon
: constant Character := ':'; -- Character'Val(58)
Semicolon
: constant Character := ';'; -- Character'Val(59)
Less_Than_Sign
: constant Character := '<'; -- Character'Val(60)
Equals_Sign
: constant Character := '='; -- Character'Val(61)
Greater_Than_Sign
: constant Character := '>'; -- Character'Val(62)
Question
: constant Character := '?'; -- Character'Val(63)
Commercial_At
: constant Character := '@'; -- Character'Val(64)
11 -- Letters 'A' through 'Z' are at positions 65 through 90
12 Left_Square_Bracket
: constant Character := '['; -- Character'Val(91)
Reverse_Solidus
: constant Character := '\'; -- Character'Val(92)
Right_Square_Bracket
: constant Character := ']'; -- Character'Val(93)
Circumflex
: constant Character := '^'; -- Character'Val(94)
Low_Line
: constant Character := '_'; -- Character'Val(95)
13 Grave
: constant Character := '`'; -- Character'Val(96)
LC_A
: constant Character := 'a'; -- Character'Val(97)
LC_B
: constant Character := 'b'; -- Character'Val(98)
LC_C
: constant Character := 'c'; -- Character'Val(99)
LC_D
: constant Character := 'd'; -- Character'Val(100)
LC_E
: constant Character := 'e'; -- Character'Val(101)
LC_F
: constant Character := 'f'; -- Character'Val(102)
LC_G
: constant Character := 'g'; -- Character'Val(103)
LC_H
: constant Character := 'h'; -- Character'Val(104)
LC_I
: constant Character := 'i'; -- Character'Val(105)
LC_J
: constant Character := 'j'; -- Character'Val(106)
LC_K
: constant Character := 'k'; -- Character'Val(107)
LC_L
: constant Character := 'l'; -- Character'Val(108)
LC_M
: constant Character := 'm'; -- Character'Val(109)
LC_N
: constant Character := 'n'; -- Character'Val(110)
LC_O
: constant Character := 'o'; -- Character'Val(111)
14 LC_P
: constant Character := 'p'; -- Character'Val(112)
LC_Q
: constant Character := 'q'; -- Character'Val(113)
LC_R
: constant Character := 'r'; -- Character'Val(114)
LC_S
: constant Character := 's'; -- Character'Val(115)
LC_T
: constant Character := 't'; -- Character'Val(116)
LC_U
: constant Character := 'u'; -- Character'Val(117)
LC_V
: constant Character := 'v'; -- Character'Val(118)
LC_W
: constant Character := 'w'; -- Character'Val(119)
LC_X
: constant Character := 'x'; -- Character'Val(120)
LC_Y
: constant Character := 'y'; -- Character'Val(121)
LC_Z
: constant Character := 'z'; -- Character'Val(122)
Left_Curly_Bracket
: constant Character := '{'; -- Character'Val(123)
Vertical_Line
: constant Character := '|'; -- Character'Val(124)
Right_Curly_Bracket
: constant Character := '}'; -- Character'Val(125)
Tilde
: constant Character := '~'; -- Character'Val(126)
DEL : constant Character := Character'Val(127);
15 -- ISO 6429 control characters:{control character (a category of Character)
[partial]}
16 IS4 : Character renames FS;
IS3 : Character renames GS;
IS2 : Character renames RS;
IS1 : Character renames US;
17 Reserved_128 : constant Character := Character'Val(128);
Reserved_129 : constant Character := Character'Val(129);
BPH : constant Character := Character'Val(130);
NBH : constant Character := Character'Val(131);
Reserved_132 : constant Character := Character'Val(132);
NEL : constant Character := Character'Val(133);
SSA : constant Character := Character'Val(134);
ESA : constant Character := Character'Val(135);
HTS : constant Character := Character'Val(136);
HTJ : constant Character := Character'Val(137);
VTS : constant Character := Character'Val(138);
PLD : constant Character := Character'Val(139);
PLU : constant Character := Character'Val(140);
RI : constant Character := Character'Val(141);
SS2 : constant Character := Character'Val(142);
SS3 : constant Character := Character'Val(143);
18 DCS : constant Character := Character'Val(144);
PU1 : constant Character := Character'Val(145);
PU2 : constant Character := Character'Val(146);
STS : constant Character := Character'Val(147);
CCH : constant Character := Character'Val(148);
MW : constant Character := Character'Val(149);
SPA : constant Character := Character'Val(150);
EPA : constant Character := Character'Val(151);
19 SOS : constant Character := Character'Val(152);
Reserved_153 : constant Character := Character'Val(153);
SCI : constant Character := Character'Val(154);
CSI : constant Character := Character'Val(155);
ST : constant Character := Character'Val(156);
OSC : constant Character := Character'Val(157);
PM : constant Character := Character'Val(158);
APC : constant Character := Character'Val(159);
20 -- Other graphic characters:
21 -- Character positions 160 (16#A0#) .. 175 (16#AF#):
No_Break_Space
: constant Character := ' '; --Character'Val(160)
NBSP : Character renames No_Break_Space;
Inverted_Exclamation
: constant Character := '¡'; --Character'Val(161)
Cent_Sign
: constant Character := '¢'; --Character'Val(162)
Pound_Sign
: constant Character := '£'; --Character'Val(163)
Currency_Sign
: constant Character := '¤'; --Character'Val(164)
Yen_Sign
: constant Character := '¥'; --Character'Val(165)
Broken_Bar
: constant Character := '¦'; --Character'Val(166)
Section_Sign
: constant Character := '§'; --Character'Val(167)
Diaeresis
: constant Character := '¨'; --Character'Val(168)
Copyright_Sign
: constant Character := '©'; --Character'Val(169)
Feminine_Ordinal_Indicator
: constant Character := 'ª'; --Character'Val(170)
Left_Angle_Quotation
: constant Character := '«'; --Character'Val(171)
Not_Sign
: constant Character := '¬'; --Character'Val(172)
Soft_Hyphen
: constant Character := ''; --Character'Val(173)
Registered_Trade_Mark_Sign
: constant Character := '®'; --Character'Val(174)
Macron
: constant Character := '¯'; --Character'Val(175)
22 -- Character positions 176 (16#B0#) .. 191 (16#BF#):
Degree_Sign
: constant Character := '°'; --Character'Val(176)
Ring_Above : Character renames Degree_Sign;
Plus_Minus_Sign
: constant Character := '±'; --Character'Val(177)
Superscript_Two
: constant Character := '²'; --Character'Val(178)
Superscript_Three
: constant Character := '³'; --Character'Val(179)
Acute
: constant Character := '´'; --Character'Val(180)
Micro_Sign
: constant Character := 'µ'; --Character'Val(181)
Pilcrow_Sign
: constant Character := '¶'; --Character'Val(182)
Paragraph_Sign : Character renames Pilcrow_Sign;
Middle_Dot
: constant Character := '·'; --Character'Val(183)
Cedilla
: constant Character := '¸'; --Character'Val(184)
Superscript_One
: constant Character := '¹'; --Character'Val(185)
Masculine_Ordinal_Indicator
: constant Character := 'º'; --Character'Val(186)
Right_Angle_Quotation
: constant Character := '»'; --Character'Val(187)
Fraction_One_Quarter
: constant Character := '¼'; --Character'Val(188)
Fraction_One_Half
: constant Character := '½'; --Character'Val(189)
Fraction_Three_Quarters
: constant Character := '¾'; --Character'Val(190)
Inverted_Question
: constant Character := '¿'; --Character'Val(191)
23 -- Character positions 192 (16#C0#) .. 207 (16#CF#):
UC_A_Grave
: constant Character := 'À'; --Character'Val(192)
UC_A_Acute
: constant Character := 'Á'; --Character'Val(193)
UC_A_Circumflex
: constant Character := 'Â'; --Character'Val(194)
UC_A_Tilde
: constant Character := 'Ã'; --Character'Val(195)
UC_A_Diaeresis
: constant Character := 'Ä'; --Character'Val(196)
UC_A_Ring
: constant Character := 'Å'; --Character'Val(197)
UC_AE_Diphthong
: constant Character := 'Æ'; --Character'Val(198)
UC_C_Cedilla
: constant Character := 'Ç'; --Character'Val(199)
UC_E_Grave
: constant Character := 'È'; --Character'Val(200)
UC_E_Acute
: constant Character := 'É'; --Character'Val(201)
UC_E_Circumflex
: constant Character := 'Ê'; --Character'Val(202)
UC_E_Diaeresis
: constant Character := 'Ë'; --Character'Val(203)
UC_I_Grave
: constant Character := 'Ì'; --Character'Val(204)
UC_I_Acute
: constant Character := 'Í'; --Character'Val(205)
UC_I_Circumflex
: constant Character := 'Î'; --Character'Val(206)
UC_I_Diaeresis
: constant Character := 'Ï'; --Character'Val(207)
24 -- Character positions 208 (16#D0#) .. 223 (16#DF#):
UC_Icelandic_Eth
: constant Character := 'Ð'; --Character'Val(208)
UC_N_Tilde
: constant Character := 'Ñ'; --Character'Val(209)
UC_O_Grave
: constant Character := 'Ò'; --Character'Val(210)
UC_O_Acute
: constant Character := 'Ó'; --Character'Val(211)
UC_O_Circumflex
: constant Character := 'Ô'; --Character'Val(212)
UC_O_Tilde
: constant Character := 'Õ'; --Character'Val(213)
UC_O_Diaeresis
: constant Character := 'Ö'; --Character'Val(214)
Multiplication_Sign
: constant Character := '×'; --Character'Val(215)
UC_O_Oblique_Stroke
: constant Character := 'Ø'; --Character'Val(216)
UC_U_Grave
: constant Character := 'Ù'; --Character'Val(217)
UC_U_Acute
: constant Character := 'Ú'; --Character'Val(218)
UC_U_Circumflex
: constant Character := 'Û'; --Character'Val(219)
UC_U_Diaeresis
: constant Character := 'Ü'; --Character'Val(220)
UC_Y_Acute
: constant Character := 'Ý'; --Character'Val(221)
UC_Icelandic_Thorn
: constant Character := 'Þ'; --Character'Val(222)
LC_German_Sharp_S
: constant Character := 'ß'; --Character'Val(223)
25 -- Character positions 224 (16#E0#) .. 239 (16#EF#):
LC_A_Grave
: constant Character := 'à'; --Character'Val(224)
LC_A_Acute
: constant Character := 'á'; --Character'Val(225)
LC_A_Circumflex
: constant Character := 'â'; --Character'Val(226)
LC_A_Tilde
: constant Character := 'ã'; --Character'Val(227)
LC_A_Diaeresis
: constant Character := 'ä'; --Character'Val(228)
LC_A_Ring
: constant Character := 'å'; --Character'Val(229)
LC_AE_Diphthong
: constant Character := 'æ'; --Character'Val(230)
LC_C_Cedilla
: constant Character := 'ç'; --Character'Val(231)
LC_E_Grave
: constant Character := 'è'; --Character'Val(232)
LC_E_Acute
: constant Character := 'é'; --Character'Val(233)
LC_E_Circumflex
: constant Character := 'ê'; --Character'Val(234)
LC_E_Diaeresis
: constant Character := 'ë'; --Character'Val(235)
LC_I_Grave
: constant Character := 'ì'; --Character'Val(236)
LC_I_Acute
: constant Character := 'í'; --Character'Val(237)
LC_I_Circumflex
: constant Character := 'î'; --Character'Val(238)
LC_I_Diaeresis
: constant Character := 'ï'; --Character'Val(239)
26 -- Character positions 240 (16#F0#) .. 255 (16#FF#):
LC_Icelandic_Eth
: constant Character := 'ð'; --Character'Val(240)
LC_N_Tilde
: constant Character := 'ñ'; --Character'Val(241)
LC_O_Grave
: constant Character := 'ò'; --Character'Val(242)
LC_O_Acute
: constant Character := 'ó'; --Character'Val(243)
LC_O_Circumflex
: constant Character := 'ô'; --Character'Val(244)
LC_O_Tilde
: constant Character := 'õ'; --Character'Val(245)
LC_O_Diaeresis
: constant Character := 'ö'; --Character'Val(246)
Division_Sign
: constant Character := '÷'; --Character'Val(247)
LC_O_Oblique_Stroke
: constant Character := 'ø'; --Character'Val(248)
LC_U_Grave
: constant Character := 'ù'; --Character'Val(249)
LC_U_Acute
: constant Character := 'ú'; --Character'Val(250)
LC_U_Circumflex
: constant Character := 'û'; --Character'Val(251)
LC_U_Diaeresis
: constant Character := 'ü'; --Character'Val(252)
LC_Y_Acute
: constant Character := 'ý'; --Character'Val(253)
LC_Icelandic_Thorn
: constant Character := 'þ'; --Character'Val(254)
LC_Y_Diaeresis
: constant Character := 'ÿ'; --Character'Val(255)
end Ada.Characters.Latin_1;
Implementation Permissions
27 An implementation may provide additional packages as children of
Ada.Characters, to declare names for the symbols of the local character set or
other character sets.
A.3.4 The Package Characters.Conversions
Static Semantics
1/2 {AI95-00395-01} The library package Characters.Conversions has the
following declaration:
2/2 package Ada.Characters.Conversions is
pragma Pure(Conversions);
3/2 function Is_Character
(Item : in Wide_Character) return Boolean;
function Is_String
(Item : in Wide_String) return Boolean;
function Is_Character
(Item : in Wide_Wide_Character) return Boolean;
function Is_String
(Item : in Wide_Wide_String) return Boolean;
function Is_Wide_Character (Item : in Wide_Wide_Character)
return Boolean;
function Is_Wide_String (Item : in Wide_Wide_String)
return Boolean;
4/2 function To_Wide_Character
(Item : in Character) return Wide_Character;
function To_Wide_String
(Item : in String) return Wide_String;
function To_Wide_Wide_Character (Item : in Character)
return Wide_Wide_Character;
function To_Wide_Wide_String (Item : in String)
return Wide_Wide_String;
function To_Wide_Wide_Character (Item : in Wide_Character)
return Wide_Wide_Character;
function To_Wide_Wide_String (Item : in Wide_String)
return Wide_Wide_String;
5/2 function To_Character (Item : in Wide_Character;
Substitute : in Character := ' ')
return Character;
function To_String (Item : in Wide_String;
Substitute : in Character := ' ')
return String;
function To_Character (Item : in Wide_Wide_Character;
Substitute : in Character := ' ')
return Character;
function To_String (Item : in Wide_Wide_String;
Substitute : in Character := ' ')
return String;
function To_Wide_Character (Item : in Wide_Wide_Character;
Substitute : in Wide_Character := ' ')
return Wide_Character;
function To_Wide_String (Item : in Wide_Wide_String;
Substitute : in Wide_Character := ' ')
return Wide_String;
6/2 end Ada.Characters.Conversions;
7/2 {AI95-00395-01} The functions in package Characters.Conversions test
Wide_Wide_Character or Wide_Character values for membership in Wide_Character
or Character, or convert between corresponding characters of
Wide_Wide_Character, Wide_Character, and Character.
8/2 function Is_Character (Item : in Wide_Character) return Boolean;
9/2 {AI95-00395-01} Returns True if Wide_Character'Pos(Item) <=
Character'Pos(Character'Last).
10/2 function Is_Character (Item : in Wide_Wide_Character) return Boolean;
11/2 {AI95-00395-01} Returns True if Wide_Wide_Character'Pos(Item) <=
Character'Pos(Character'Last).
12/2 function Is_Wide_Character (Item : in Wide_Wide_Character) return Boolean;
13/2 {AI95-00395-01} Returns True if Wide_Wide_Character'Pos(Item) <=
Wide_Character'Pos(Wide_Character'Last).
14/2 function Is_String (Item : in Wide_String) return Boolean;
function Is_String (Item : in Wide_Wide_String) return Boolean;
15/2 {AI95-00395-01} Returns True if Is_Character(Item(I)) is True for
each I in Item'Range.
16/2 function Is_Wide_String (Item : in Wide_Wide_String) return Boolean;
17/2 {AI95-00395-01} Returns True if Is_Wide_Character(Item(I)) is True
for each I in Item'Range.
18/2 function To_Character (Item : in Wide_Character;
Substitute : in Character := ' ') return Character;
function To_Character (Item : in Wide_Wide_Character;
Substitute : in Character := ' ') return Character;
19/2 {AI95-00395-01} Returns the Character corresponding to Item if
Is_Character(Item), and returns the Substitute Character otherwise.
20/2 function To_Wide_Character (Item : in Character) return Wide_Character;
21/2 {AI95-00395-01} Returns the Wide_Character X such that
Character'Pos(Item) = Wide_Character'Pos (X).
22/2 function To_Wide_Character (Item : in Wide_Wide_Character;
Substitute : in Wide_Character := ' ')
return Wide_Character;
23/2 {AI95-00395-01} Returns the Wide_Character corresponding to Item
if Is_Wide_Character(Item), and returns the Substitute
Wide_Character otherwise.
24/2 function To_Wide_Wide_Character (Item : in Character)
return Wide_Wide_Character;
25/2 {AI95-00395-01} Returns the Wide_Wide_Character X such that
Character'Pos(Item) = Wide_Wide_Character'Pos (X).
26/2 function To_Wide_Wide_Character (Item : in Wide_Character)
return Wide_Wide_Character;
27/2 {AI95-00395-01} Returns the Wide_Wide_Character X such that
Wide_Character'Pos(Item) = Wide_Wide_Character'Pos (X).
28/2 function To_String (Item : in Wide_String;
Substitute : in Character := ' ') return String;
function To_String (Item : in Wide_Wide_String;
Substitute : in Character := ' ') return String;
29/2 {AI95-00395-01} Returns the String whose range is 1..Item'Length
and each of whose elements is given by To_Character of the
corresponding element in Item.
30/2 function To_Wide_String (Item : in String) return Wide_String;
31/2 {AI95-00395-01} Returns the Wide_String whose range is
1..Item'Length and each of whose elements is given by
To_Wide_Character of the corresponding element in Item.
32/2 function To_Wide_String (Item : in Wide_Wide_String;
Substitute : in Wide_Character := ' ')
return Wide_String;
33/2 {AI95-00395-01} Returns the Wide_String whose range is
1..Item'Length and each of whose elements is given by
To_Wide_Character of the corresponding element in Item with the
given Substitute Wide_Character.
34/2 function To_Wide_Wide_String (Item : in String) return Wide_Wide_String;
function To_Wide_Wide_String (Item : in Wide_String)
return Wide_Wide_String;
35/2 {AI95-00395-01} Returns the Wide_Wide_String whose range is
1..Item'Length and each of whose elements is given by
To_Wide_Wide_Character of the corresponding element in Item.
Extensions to Ada 95
35.a/2 {AI95-00395-01} {extensions to Ada 95} The package
Characters.Conversions is new, replacing functions previously
found in Characters.Handling.
A.4 String Handling
1/2 {AI95-00285-01} This clause presents the specifications of the package
Strings and several child packages, which provide facilities for dealing with
string data. Fixed-length, bounded-length, and unbounded-length strings are
supported, for String, Wide_String, and Wide_Wide_String. The string-handling
subprograms include searches for pattern strings and for characters in
program-specified sets, translation (via a character-to-character mapping),
and transformation (replacing, inserting, overwriting, and deleting of
substrings).
Extensions to Ada 83
1.a {extensions to Ada 83} This clause is new to Ada 95.
Wording Changes from Ada 95
1.b/2 {AI95-00285-01} Included Wide_Wide_String in this description; the
individual changes are documented as extensions as needed.
A.4.1 The Package Strings
1 The package Strings provides declarations common to the string handling
packages.
Static Semantics
2 The library package Strings has the following declaration:
3 package Ada.Strings is
pragma Pure(Strings);
4/2 {AI95-00285-01} Space : constant Character := ' ';
Wide_Space : constant Wide_Character := ' ';
Wide_Wide_Space : constant Wide_Wide_Character := ' ';
5 Length_Error, Pattern_Error, Index_Error, Translation_Error
: exception;
6 type Alignment is (Left, Right, Center);
type Truncation is (Left, Right, Error);
type Membership is (Inside, Outside);
type Direction is (Forward, Backward);
type Trim_End is (Left, Right, Both);
end Ada.Strings;
Incompatibilities With Ada 95
6.a/2 {AI95-00285-01} {incompatibilities with Ada 95} Constant
Wide_Wide_Space is newly added to Ada.Strings. If Ada.Strings is
referenced in a use_clause, and an entity E with a
defining_identifier of Wide_Wide_Space is defined in a package
that is also referenced in a use_clause, the entity E may no
longer be use-visible, resulting in errors. This should be rare
and is easily fixed if it does occur.
A.4.2 The Package Strings.Maps
1 The package Strings.Maps defines the types, operations, and other entities
needed for character sets and character-to-character mappings.
Static Semantics
2 The library package Strings.Maps has the following declaration:
3/2 {AI95-00362-01} package Ada.Strings.Maps is
pragma Pure(Maps);
4/2 {AI95-00161-01} -- Representation for a set of character values:
type Character_Set is private;
pragma Preelaborable_Initialization(Character_Set);
5 Null_Set : constant Character_Set;
6 type Character_Range is
record
Low : Character;
High : Character;
end record;
-- Represents Character range Low..High
7 type Character_Ranges
is array (Positive range <>) of Character_Range;
8 function To_Set
(Ranges : in Character_Ranges)return Character_Set;
9 function To_Set
(Span : in Character_Range)return Character_Set;
10 function To_Ranges
(Set : in Character_Set) return Character_Ranges;
11 function "=" (Left, Right : in Character_Set) return Boolean;
12 function "not" (Right : in Character_Set) return Character_Set;
function "and" (Left, Right : in Character_Set) return Character_Set;
function "or" (Left, Right : in Character_Set) return Character_Set;
function "xor" (Left, Right : in Character_Set) return Character_Set;
function "-" (Left, Right : in Character_Set) return Character_Set;
13 function Is_In (Element : in Character;
Set : in Character_Set)
return Boolean;
14 function Is_Subset (Elements : in Character_Set;
Set : in Character_Set)
return Boolean;
15 function "<=" (Left : in Character_Set;
Right : in Character_Set)
return Boolean renames Is_Subset;
16 -- Alternative representation for a set of character values:
subtype Character_Sequence is String;
17 function To_Set
(Sequence : in Character_Sequence)return Character_Set;
18 function To_Set
(Singleton : in Character) return Character_Set;
19 function To_Sequence
(Set : in Character_Set) return Character_Sequence;
20/2 {AI95-00161-01}
-- Representation for a character to character mapping:
type Character_Mapping is private;
pragma Preelaborable_Initialization(Character_Mapping);
21 function Value (Map : in Character_Mapping;
Element : in Character)
return Character;
22 Identity : constant Character_Mapping;
23 function To_Mapping (From, To : in Character_Sequence)
return Character_Mapping;
24 function To_Domain (Map : in Character_Mapping)
return Character_Sequence;
function To_Range (Map : in Character_Mapping)
return Character_Sequence;
25 type Character_Mapping_Function is
access function (From : in Character) return Character;
26 private
... -- not specified by the language
end Ada.Strings.Maps;
27 An object of type Character_Set represents a set of characters.
28 Null_Set represents the set containing no characters.
29 An object Obj of type Character_Range represents the set of characters in
the range Obj.Low .. Obj.High.
30 An object Obj of type Character_Ranges represents the union of the sets
corresponding to Obj(I) for I in Obj'Range.
31 function To_Set (Ranges : in Character_Ranges) return Character_Set;
32 If Ranges'Length=0 then Null_Set is returned; otherwise the
returned value represents the set corresponding to Ranges.
33 function To_Set (Span : in Character_Range) return Character_Set;
34 The returned value represents the set containing each character in
Span.
35 function To_Ranges (Set : in Character_Set) return Character_Ranges;
36 If Set = Null_Set then an empty Character_Ranges array is
returned; otherwise the shortest array of contiguous ranges of
Character values in Set, in increasing order of Low, is returned.
37 function "=" (Left, Right : in Character_Set) return Boolean;
38 The function "=" returns True if Left and Right represent
identical sets, and False otherwise.
39 Each of the logical operators "not", "and", "or", and "xor" returns a
Character_Set value that represents the set obtained by applying the
corresponding operation to the set(s) represented by the parameter(s) of the
operator. "-"(Left, Right) is equivalent to "and"(Left, "not"(Right)).
39.a Reason: The set minus operator is provided for efficiency.
40 function Is_In (Element : in Character;
Set : in Character_Set);
return Boolean;
41 Is_In returns True if Element is in Set, and False otherwise.
42 function Is_Subset (Elements : in Character_Set;
Set : in Character_Set)
return Boolean;
43 Is_Subset returns True if Elements is a subset of Set, and False
otherwise.
44 subtype Character_Sequence is String;
45 The Character_Sequence subtype is used to portray a set of
character values and also to identify the domain and range of a
character mapping.
45.a Reason: Although a named subtype is redundant - the predefined
type String could have been used for the parameter to To_Set and
To_Mapping below - the use of a differently named subtype
identifies the intended purpose of the parameter.
46 function To_Set (Sequence : in Character_Sequence) return Character_Set;
function To_Set (Singleton : in Character) return Character_Set;
47 Sequence portrays the set of character values that it explicitly
contains (ignoring duplicates). Singleton portrays the set
comprising a single Character. Each of the To_Set functions
returns a Character_Set value that represents the set portrayed by
Sequence or Singleton.
48 function To_Sequence (Set : in Character_Set) return Character_Sequence;
49 The function To_Sequence returns a Character_Sequence value
containing each of the characters in the set represented by Set,
in ascending order with no duplicates.
50 type Character_Mapping is private;
51 An object of type Character_Mapping represents a
Character-to-Character mapping.
52 function Value (Map : in Character_Mapping;
Element : in Character)
return Character;
53 The function Value returns the Character value to which Element
maps with respect to the mapping represented by Map.
54 {match (a character to a pattern character)} A character C matches a
pattern character P with respect to a given Character_Mapping value Map if
Value(Map, C) = P. {match (a string to a pattern string)} A string S matches a
pattern string P with respect to a given Character_Mapping if their lengths
are the same and if each character in S matches its corresponding character in
the pattern string P.
54.a Discussion: In an earlier version of the string handling packages,
the definition of matching was symmetrical, namely C matches P if
Value(Map,C) = Value(Map,P). However, applying the mapping to the
pattern was confusing according to some reviewers. Furthermore, if
the symmetrical version is needed, it can be achieved by applying
the mapping to the pattern (via translation) prior to passing it
as a parameter.
55 String handling subprograms that deal with character mappings have
parameters whose type is Character_Mapping.
56 Identity : constant Character_Mapping;
57 Identity maps each Character to itself.
58 function To_Mapping (From, To : in Character_Sequence)
return Character_Mapping;
59 To_Mapping produces a Character_Mapping such that each element of
From maps to the corresponding element of To, and each other
character maps to itself. If From'Length /= To'Length, or if some
character is repeated in From, then Translation_Error is
propagated.
60 function To_Domain (Map : in Character_Mapping) return Character_Sequence;
61 To_Domain returns the shortest Character_Sequence value D such
that each character not in D maps to itself, and such that the
characters in D are in ascending order. The lower bound of D is 1.
62 function To_Range (Map : in Character_Mapping) return Character_Sequence;
63/1 {8652/0048} {AI95-00151-01} To_Range returns the
Character_Sequence value R, such that if D = To_Domain(Map), then
R has the same bounds as D, and D(I) maps to R(I) for each I in
D'Range.
64 An object F of type Character_Mapping_Function maps a Character value C to
the Character value F.all(C), which is said to match C with respect to mapping
function F.
{match (a character to a pattern character, with respect to a character mapping function)
}
NOTES
65 7 Character_Mapping and Character_Mapping_Function are used both for
character equivalence mappings in the search subprograms (such as for
case insensitivity) and as transformational mappings in the Translate
subprograms.
66 8 To_Domain(Identity) and To_Range(Identity) each returns the null
string.
66.a Reason: Package Strings.Maps is not pure, since it declares an
access-to-subprogram type.
Examples
67 To_Mapping("ABCD", "ZZAB") returns a Character_Mapping that maps 'A' and
'B' to 'Z', 'C' to 'A', 'D' to 'B', and each other Character to itself.
Extensions to Ada 95
67.a/2 {AI95-00161-01} {extensions to Ada 95} Amendment Correction: Added
pragma Preelaborable_Initialization to types Character_Set and
Character_Mapping, so that they can be used to declare
default-initialized objects in preelaborated units.
67.b/2 {AI95-00362-01} Strings.Maps is now Pure, so it can be used in
pure units.
Wording Changes from Ada 95
67.c/2 {8652/0048} {AI95-00151-01} Corrigendum: Corrected the definition
of the range of the result of To_Range, since the Ada 95
definition makes no sense.
A.4.3 Fixed-Length String Handling
1 The language-defined package Strings.Fixed provides string-handling
subprograms for fixed-length strings; that is, for values of type
Standard.String. Several of these subprograms are procedures that modify the
contents of a String that is passed as an out or an in out parameter; each has
additional parameters to control the effect when the logical length of the
result differs from the parameter's length.
2 For each function that returns a String, the lower bound of the returned
value is 1.
2.a/2 Discussion: {AI95-00114-01} Most operations that yield a String
are provided both as a function and as a procedure. The functional
form is possibly a more aesthetic style but may introduce overhead
due to extra copying or dynamic memory usage in some
implementations. Thus a procedural form, with an in out parameter
so that all copying is done `in place', is also supplied.
3 The basic model embodied in the package is that a fixed-length string
comprises significant characters and possibly padding (with space characters)
on either or both ends. When a shorter string is copied to a longer string,
padding is inserted, and when a longer string is copied to a shorter one,
padding is stripped. The Move procedure in Strings.Fixed, which takes a String
as an out parameter, allows the programmer to control these effects. Similar
control is provided by the string transformation procedures.
Static Semantics
4 The library package Strings.Fixed has the following declaration:
5 with Ada.Strings.Maps;
package Ada.Strings.Fixed is
pragma Preelaborate(Fixed);
6 -- "Copy" procedure for strings of possibly different lengths
7 procedure Move (Source : in String;
Target : out String;
Drop : in Truncation := Error;
Justify : in Alignment := Left;
Pad : in Character := Space);
8 -- Search subprograms
8.1/2 {AI95-00301-01} function Index (Source : in String;
Pattern : in String;
From : in Positive;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping := Maps.Identity)
return Natural;
8.2/2 {AI95-00301-01} function Index (Source : in String;
Pattern : in String;
From : in Positive;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
9 function Index (Source : in String;
Pattern : in String;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping
:= Maps.Identity)
return Natural;
10 function Index (Source : in String;
Pattern : in String;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
10.1/2 {AI95-00301-01} function Index (Source : in String;
Set : in Maps.Character_Set;
From : in Positive;
Test : in Membership := Inside;
Going : in Direction := Forward)
return Natural;
11 function Index (Source : in String;
Set : in Maps.Character_Set;
Test : in Membership := Inside;
Going : in Direction := Forward)
return Natural;
11.1/2 {AI95-00301-01} function Index_Non_Blank (Source : in String;
From : in Positive;
Going : in Direction := Forward)
return Natural;
12 function Index_Non_Blank (Source : in String;
Going : in Direction := Forward)
return Natural;
13 function Count (Source : in String;
Pattern : in String;
Mapping : in Maps.Character_Mapping
:= Maps.Identity)
return Natural;
14 function Count (Source : in String;
Pattern : in String;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
15 function Count (Source : in String;
Set : in Maps.Character_Set)
return Natural;
16 procedure Find_Token (Source : in String;
Set : in Maps.Character_Set;
Test : in Membership;
First : out Positive;
Last : out Natural);
17 -- String translation subprograms
18 function Translate (Source : in String;
Mapping : in Maps.Character_Mapping)
return String;
19 procedure Translate (Source : in out String;
Mapping : in Maps.Character_Mapping);
20 function Translate (Source : in String;
Mapping : in Maps.Character_Mapping_Function)
return String;
21 procedure Translate (Source : in out String;
Mapping : in Maps.Character_Mapping_Function);
22 -- String transformation subprograms
23 function Replace_Slice (Source : in String;
Low : in Positive;
High : in Natural;
By : in String)
return String;
24 procedure Replace_Slice (Source : in out String;
Low : in Positive;
High : in Natural;
By : in String;
Drop : in Truncation := Error;
Justify : in Alignment := Left;
Pad : in Character := Space);
25 function Insert (Source : in String;
Before : in Positive;
New_Item : in String)
return String;
26 procedure Insert (Source : in out String;
Before : in Positive;
New_Item : in String;
Drop : in Truncation := Error);
27 function Overwrite (Source : in String;
Position : in Positive;
New_Item : in String)
return String;
28 procedure Overwrite (Source : in out String;
Position : in Positive;
New_Item : in String;
Drop : in Truncation := Right);
29 function Delete (Source : in String;
From : in Positive;
Through : in Natural)
return String;
30 procedure Delete (Source : in out String;
From : in Positive;
Through : in Natural;
Justify : in Alignment := Left;
Pad : in Character := Space);
31 --String selector subprograms
function Trim (Source : in String;
Side : in Trim_End)
return String;
32 procedure Trim (Source : in out String;
Side : in Trim_End;
Justify : in Alignment := Left;
Pad : in Character := Space);
33 function Trim (Source : in String;
Left : in Maps.Character_Set;
Right : in Maps.Character_Set)
return String;
34 procedure Trim (Source : in out String;
Left : in Maps.Character_Set;
Right : in Maps.Character_Set;
Justify : in Alignment := Strings.Left;
Pad : in Character := Space);
35 function Head (Source : in String;
Count : in Natural;
Pad : in Character := Space)
return String;
36 procedure Head (Source : in out String;
Count : in Natural;
Justify : in Alignment := Left;
Pad : in Character := Space);
37 function Tail (Source : in String;
Count : in Natural;
Pad : in Character := Space)
return String;
38 procedure Tail (Source : in out String;
Count : in Natural;
Justify : in Alignment := Left;
Pad : in Character := Space);
39 --String constructor functions
40 function "*" (Left : in Natural;
Right : in Character) return String;
41 function "*" (Left : in Natural;
Right : in String) return String;
42 end Ada.Strings.Fixed;
43 The effects of the above subprograms are as follows.
44 procedure Move (Source : in String;
Target : out String;
Drop : in Truncation := Error;
Justify : in Alignment := Left;
Pad : in Character := Space);
45 The Move procedure copies characters from Source to Target. If
Source has the same length as Target, then the effect is to assign
Source to Target. If Source is shorter than Target then:
46 * If Justify=Left, then Source is copied into the first
Source'Length characters of Target.
47 * If Justify=Right, then Source is copied into the last
Source'Length characters of Target.
48 * If Justify=Center, then Source is copied into the middle
Source'Length characters of Target. In this case, if the
difference in length between Target and Source is odd, then
the extra Pad character is on the right.
49 * Pad is copied to each Target character not otherwise assigned.
50 If Source is longer than Target, then the effect is based on Drop.
51 * If Drop=Left, then the rightmost Target'Length characters of
Source are copied into Target.
52 * If Drop=Right, then the leftmost Target'Length characters of
Source are copied into Target.
53 * If Drop=Error, then the effect depends on the value of the
Justify parameter and also on whether any characters in Source
other than Pad would fail to be copied:
54 * If Justify=Left, and if each of the rightmost
Source'Length-Target'Length characters in Source is Pad,
then the leftmost Target'Length characters of Source are
copied to Target.
55 * If Justify=Right, and if each of the leftmost
Source'Length-Target'Length characters in Source is Pad,
then the rightmost Target'Length characters of Source are
copied to Target.
56 * Otherwise, Length_Error is propagated.
56.a Ramification: The Move procedure will work even if Source and
Target overlap.
56.b Reason: The order of parameters (Source before Target) corresponds
to the order in COBOL's MOVE verb.
56.1/2 function Index (Source : in String;
Pattern : in String;
From : in Positive;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping := Maps.Identity)
return Natural;
function Index (Source : in String;
Pattern : in String;
From : in Positive;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
56.2/2 {AI95-00301-01} Each Index function searches, starting from From,
for a slice of Source, with length Pattern'Length, that matches
Pattern with respect to Mapping; the parameter Going indicates the
direction of the lookup. If From is not in Source'Range, then
Index_Error is propagated. If Going = Forward, then Index returns
the smallest index I which is greater than or equal to From such
that the slice of Source starting at I matches Pattern. If Going =
Backward, then Index returns the largest index I such that the
slice of Source starting at I matches Pattern and has an upper
bound less than or equal to From. If there is no such slice, then
0 is returned. If Pattern is the null string, then Pattern_Error
is propagated.
56.c/2 Discussion: There is no default parameter for From; the default
value would need to depend on other parameters (the bounds of
Source and the direction Going). It is better to use overloaded
functions rather than a special value to represent the default.
56.d/2 There is no default value for the Mapping parameter that is a
Character_Mapping_Function; if there were, a call would be
ambiguous since there is also a default for the Mapping parameter
that is a Character_Mapping.
57 function Index (Source : in String;
Pattern : in String;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping
:= Maps.Identity)
return Natural;
function Index (Source : in String;
Pattern : in String;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
58/2 {AI95-00301-01} If Going = Forward, returns
58.1/2 Index (Source, Pattern, Source'First, Forward, Mapping);
58.2/2 otherwise returns
58.3/2 Index (Source, Pattern, Source'Last, Backward, Mapping);
58.a/2 This paragraph was deleted.There is no default value for the
Mapping parameter that is a Character_Mapping_Function; if there
were, a call would be ambiguous since there is also a default for
the Mapping parameter that is a Character_Mapping.
58.4/2 function Index (Source : in String;
Set : in Maps.Character_Set;
From : in Positive;
Test : in Membership := Inside;
Going : in Direction := Forward)
return Natural;
58.5/2 {AI95-00301-01} Index searches for the first or last occurrence of
any of a set of characters (when Test=Inside), or any of the
complement of a set of characters (when Test=Outside). If From is
not in Source'Range, then Index_Error is propagated. Otherwise, it
returns the smallest index I >= From (if Going=Forward) or the
largest index I <= From (if Going=Backward) such that Source(I)
satisfies the Test condition with respect to Set; it returns 0 if
there is no such Character in Source.
59 function Index (Source : in String;
Set : in Maps.Character_Set;
Test : in Membership := Inside;
Going : in Direction := Forward)
return Natural;
60/2 {AI95-00301-01} If Going = Forward, returns
60.1/2 Index (Source, Set, Source'First, Test, Forward);
60.2/2 otherwise returns
60.3/2 Index (Source, Set, Source'Last, Test, Backward);
60.4/2 function Index_Non_Blank (Source : in String;
From : in Positive;
Going : in Direction := Forward)
return Natural;
60.5/2 {AI95-00301-01} Returns Index (Source, Maps.To_Set(Space), From,
Outside, Going);
61 function Index_Non_Blank (Source : in String;
Going : in Direction := Forward)
return Natural;
62 Returns Index(Source, Maps.To_Set(Space), Outside, Going)
63 function Count (Source : in String;
Pattern : in String;
Mapping : in Maps.Character_Mapping
:= Maps.Identity)
return Natural;
function Count (Source : in String;
Pattern : in String;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
64 Returns the maximum number of nonoverlapping slices of Source that
match Pattern with respect to Mapping. If Pattern is the null
string then Pattern_Error is propagated.
64.a Reason: We say `maximum number' because it is possible to slice a
source string in different ways yielding different numbers of
matches. For example if Source is "ABABABA" and Pattern is "ABA",
then Count yields 2, although there is a partitioning of Source
that yields just 1 match, for the middle slice. Saying `maximum
number' is equivalent to saying that the pattern match starts
either at the low index or the high index position.
65 function Count (Source : in String;
Set : in Maps.Character_Set)
return Natural;
66 Returns the number of occurrences in Source of characters that are
in Set.
67 procedure Find_Token (Source : in String;
Set : in Maps.Character_Set;
Test : in Membership;
First : out Positive;
Last : out Natural);
68/1 {8652/0049} {AI95-00128-01} Find_Token returns in First and Last
the indices of the beginning and end of the first slice of Source
all of whose elements satisfy the Test condition, and such that
the elements (if any) immediately before and after the slice do
not satisfy the Test condition. If no such slice exists, then the
value returned for Last is zero, and the value returned for First
is Source'First; however, if Source'First is not in Positive then
Constraint_Error {Constraint_Error (raised by failure of run-time check)
} is raised.
69 function Translate (Source : in String;
Mapping : in Maps.Character_Mapping)
return String;
function Translate (Source : in String;
Mapping : in Maps.Character_Mapping_Function)
return String;
70 Returns the string S whose length is Source'Length and such that
S(I) is the character to which Mapping maps the corresponding
element of Source, for I in 1..Source'Length.
71 procedure Translate (Source : in out String;
Mapping : in Maps.Character_Mapping);
procedure Translate (Source : in out String;
Mapping : in Maps.Character_Mapping_Function);
72 Equivalent to Source := Translate(Source, Mapping).
73 function Replace_Slice (Source : in String;
Low : in Positive;
High : in Natural;
By : in String)
return String;
74/1 {8652/0049} {AI95-00128-01} If Low > Source'Last+1, or High <
Source'First-1, then Index_Error is propagated. Otherwise:
74.1/1 * {8652/0049} {AI95-00128-01} If High >= Low, then the returned
string comprises Source(Source'First..Low-1) & By &
Source(High+1..Source'Last), but with lower bound 1.
74.2/1 * {8652/0049} {AI95-00128-01} If High < Low, then the returned
string is Insert(Source, Before=>Low, New_Item=>By).
75 procedure Replace_Slice (Source : in out String;
Low : in Positive;
High : in Natural;
By : in String;
Drop : in Truncation := Error;
Justify : in Alignment := Left;
Pad : in Character := Space);
76 Equivalent to Move(Replace_Slice(Source, Low, High, By), Source,
Drop, Justify, Pad).
77 function Insert (Source : in String;
Before : in Positive;
New_Item : in String)
return String;
78 Propagates Index_Error if Before is not in Source'First ..
Source'Last+1; otherwise returns Source(Source'First..Before-1) &
New_Item & Source(Before..Source'Last), but with lower bound 1.
79 procedure Insert (Source : in out String;
Before : in Positive;
New_Item : in String;
Drop : in Truncation := Error);
80 Equivalent to Move(Insert(Source, Before, New_Item), Source, Drop).
81 function Overwrite (Source : in String;
Position : in Positive;
New_Item : in String)
return String;
82 Propagates Index_Error if Position is not in Source'First ..
Source'Last+1; otherwise returns the string obtained from Source
by consecutively replacing characters starting at Position with
corresponding characters from New_Item. If the end of Source is
reached before the characters in New_Item are exhausted, the
remaining characters from New_Item are appended to the string.
83 procedure Overwrite (Source : in out String;
Position : in Positive;
New_Item : in String;
Drop : in Truncation := Right);
84 Equivalent to Move(Overwrite(Source, Position, New_Item), Source,
Drop).
85 function Delete (Source : in String;
From : in Positive;
Through : in Natural)
return String;
86/1 {8652/0049} {AI95-00128-01} If From <= Through, the returned
string is Replace_Slice(Source, From, Through, ""), otherwise it
is Source with lower bound 1.
87 procedure Delete (Source : in out String;
From : in Positive;
Through : in Natural;
Justify : in Alignment := Left;
Pad : in Character := Space);
88 Equivalent to Move(Delete(Source, From, Through), Source, Justify
=> Justify, Pad => Pad).
89 function Trim (Source : in String;
Side : in Trim_End)
return String;
90 Returns the string obtained by removing from Source all leading
Space characters (if Side = Left), all trailing Space characters
(if Side = Right), or all leading and trailing Space characters
(if Side = Both).
91 procedure Trim (Source : in out String;
Side : in Trim_End;
Justify : in Alignment := Left;
Pad : in Character := Space);
92 Equivalent to Move(Trim(Source, Side), Source, Justify=>Justify,
Pad=>Pad).
93 function Trim (Source : in String;
Left : in Maps.Character_Set;
Right : in Maps.Character_Set)
return String;
94 Returns the string obtained by removing from Source all leading
characters in Left and all trailing characters in Right.
95 procedure Trim (Source : in out String;
Left : in Maps.Character_Set;
Right : in Maps.Character_Set;
Justify : in Alignment := Strings.Left;
Pad : in Character := Space);
96 Equivalent to Move(Trim(Source, Left, Right), Source, Justify =>
Justify, Pad=>Pad).
97 function Head (Source : in String;
Count : in Natural;
Pad : in Character := Space)
return String;
98 Returns a string of length Count. If Count <= Source'Length, the
string comprises the first Count characters of Source. Otherwise
its contents are Source concatenated with Count-Source'Length Pad
characters.
99 procedure Head (Source : in out String;
Count : in Natural;
Justify : in Alignment := Left;
Pad : in Character := Space);
100 Equivalent to Move(Head(Source, Count, Pad), Source, Drop=>Error,
Justify=>Justify, Pad=>Pad).
101 function Tail (Source : in String;
Count : in Natural;
Pad : in Character := Space)
return String;
102 Returns a string of length Count. If Count <= Source'Length, the
string comprises the last Count characters of Source. Otherwise
its contents are Count-Source'Length Pad characters concatenated
with Source.
103 procedure Tail (Source : in out String;
Count : in Natural;
Justify : in Alignment := Left;
Pad : in Character := Space);
104 Equivalent to Move(Tail(Source, Count, Pad), Source, Drop=>Error,
Justify=>Justify, Pad=>Pad).
105 function "*" (Left : in Natural;
Right : in Character) return String;
function "*" (Left : in Natural;
Right : in String) return String;
106/1 {8652/0049} {AI95-00128-01} These functions replicate a character
or string a specified number of times. The first function returns
a string whose length is Left and each of whose elements is Right.
The second function returns a string whose length is
Left*Right'Length and whose value is the null string if Left = 0
and otherwise is (Left-1)*Right & Right with lower bound 1.
NOTES
107 9 In the Index and Count functions taking Pattern and Mapping
parameters, the actual String parameter passed to Pattern should
comprise characters occurring as target characters of the mapping.
Otherwise the pattern will not match.
108 10 In the Insert subprograms, inserting at the end of a string is
obtained by passing Source'Last+1 as the Before parameter.
109 11 {Constraint_Error (raised by failure of run-time check)} If a null
Character_Mapping_Function is passed to any of the string handling
subprograms, Constraint_Error is propagated.
Incompatibilities With Ada 95
109.a/2 {AI95-00301-01} {incompatibilities with Ada 95} Overloaded
versions of Index and Index_Non_Blank are newly added to
Strings.Fixed. If Strings.Fixed is referenced in a use_clause, and
an entity E with a defining_identifier of Index or Index_Non_Blank
is defined in a package that is also referenced in a use_clause,
the entity E may no longer be use-visible, resulting in errors.
This should be rare and is easily fixed if it does occur.
Wording Changes from Ada 95
109.b/2 {8652/0049} {AI95-00128-01} Corrigendum: Clarified that Find_Token
may raise Constraint_Error if Source'First is not in Positive
(which is only possible for a null string).
109.c/2 {8652/0049} {AI95-00128-01} Corrigendum: Clarified that
Replace_Slice, Delete, and "*" always return a string with lower
bound 1.
A.4.4 Bounded-Length String Handling
1 The language-defined package Strings.Bounded provides a generic package
each of whose instances yields a private type Bounded_String and a set of
operations. An object of a particular Bounded_String type represents a String
whose low bound is 1 and whose length can vary conceptually between 0 and a
maximum size established at the generic instantiation. The subprograms for
fixed-length string handling are either overloaded directly for
Bounded_String, or are modified as needed to reflect the variability in
length. Additionally, since the Bounded_String type is private, appropriate
constructor and selector operations are provided.
1.a Reason: Strings.Bounded declares an inner generic package, versus
itself being directly a generic child of Strings, in order to
retain compatibility with a version of the string-handling
packages that is generic with respect to the character and string
types.
1.b Reason: The bound of a bounded-length string is specified as a
parameter to a generic, versus as the value for a discriminant,
because of the inappropriateness of assignment and equality of
discriminated types for the copying and comparison of bounded
strings.
Static Semantics
2 The library package Strings.Bounded has the following declaration:
3 with Ada.Strings.Maps;
package Ada.Strings.Bounded is
pragma Preelaborate(Bounded);
4 generic
Max : Positive; -- Maximum length of a Bounded_String
package Generic_Bounded_Length is
5 Max_Length : constant Positive := Max;
6 type Bounded_String is private;
7 Null_Bounded_String : constant Bounded_String;
8 subtype Length_Range is Natural range 0 .. Max_Length;
9 function Length
(Source : in Bounded_String) return Length_Range;
10 -- Conversion, Concatenation, and Selection functions
11 function To_Bounded_String (Source : in String;
Drop : in Truncation := Error)
return Bounded_String;
12 function To_String (Source : in Bounded_String) return String;
12.1/2 {AI95-00301-01} procedure Set_Bounded_String
(Target : out Bounded_String;
Source : in String;
Drop : in Truncation := Error);
13 function Append (Left, Right : in Bounded_String;
Drop : in Truncation := Error)
return Bounded_String;
14 function Append (Left : in Bounded_String;
Right : in String;
Drop : in Truncation := Error)
return Bounded_String;
15 function Append (Left : in String;
Right : in Bounded_String;
Drop : in Truncation := Error)
return Bounded_String;
16 function Append (Left : in Bounded_String;
Right : in Character;
Drop : in Truncation := Error)
return Bounded_String;
17 function Append (Left : in Character;
Right : in Bounded_String;
Drop : in Truncation := Error)
return Bounded_String;
18 procedure Append (Source : in out Bounded_String;
New_Item : in Bounded_String;
Drop : in Truncation := Error);
19 procedure Append (Source : in out Bounded_String;
New_Item : in String;
Drop : in Truncation := Error);
20 procedure Append (Source : in out Bounded_String;
New_Item : in Character;
Drop : in Truncation := Error);
21 function "&" (Left, Right : in Bounded_String)
return Bounded_String;
22 function "&" (Left : in Bounded_String; Right : in String)
return Bounded_String;
23 function "&" (Left : in String; Right : in Bounded_String)
return Bounded_String;
24 function "&" (Left : in Bounded_String; Right : in Character)
return Bounded_String;
25 function "&" (Left : in Character; Right : in Bounded_String)
return Bounded_String;
26 function Element (Source : in Bounded_String;
Index : in Positive)
return Character;
27 procedure Replace_Element (Source : in out Bounded_String;
Index : in Positive;
By : in Character);
28 function Slice (Source : in Bounded_String;
Low : in Positive;
High : in Natural)
return String;
28.1/2 {AI95-00301-01} function Bounded_Slice
(Source : in Bounded_String;
Low : in Positive;
High : in Natural)
return Bounded_String;
28.2/2 {AI95-00301-01} procedure Bounded_Slice
(Source : in Bounded_String;
Target : out Bounded_String;
Low : in Positive;
High : in Natural);
29 function "=" (Left, Right : in Bounded_String) return Boolean;
function "=" (Left : in Bounded_String; Right : in String)
return Boolean;
30 function "=" (Left : in String; Right : in Bounded_String)
return Boolean;
31 function "<" (Left, Right : in Bounded_String) return Boolean;
32 function "<" (Left : in Bounded_String; Right : in String)
return Boolean;
33 function "<" (Left : in String; Right : in Bounded_String)
return Boolean;
34 function "<=" (Left, Right : in Bounded_String) return Boolean;
35 function "<=" (Left : in Bounded_String; Right : in String)
return Boolean;
36 function "<=" (Left : in String; Right : in Bounded_String)
return Boolean;
37 function ">" (Left, Right : in Bounded_String) return Boolean;
38 function ">" (Left : in Bounded_String; Right : in String)
return Boolean;
39 function ">" (Left : in String; Right : in Bounded_String)
return Boolean;
40 function ">=" (Left, Right : in Bounded_String) return Boolean;
41 function ">=" (Left : in Bounded_String; Right : in String)
return Boolean;
42 function ">=" (Left : in String; Right : in Bounded_String)
return Boolean;
43/2 {AI95-00301-01} -- Search subprograms
43.1/2 {AI95-00301-01} function Index (Source : in Bounded_String;
Pattern : in String;
From : in Positive;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping := Maps.Identity)
return Natural;
43.2/2 {AI95-00301-01} function Index (Source : in Bounded_String;
Pattern : in String;
From : in Positive;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
44 function Index (Source : in Bounded_String;
Pattern : in String;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping
:= Maps.Identity)
return Natural;
45 function Index (Source : in Bounded_String;
Pattern : in String;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
45.1/2 {AI95-00301-01} function Index (Source : in Bounded_String;
Set : in Maps.Character_Set;
From : in Positive;
Test : in Membership := Inside;
Going : in Direction := Forward)
return Natural;
46 function Index (Source : in Bounded_String;
Set : in Maps.Character_Set;
Test : in Membership := Inside;
Going : in Direction := Forward)
return Natural;
46.1/2 {AI95-00301-01} function Index_Non_Blank
(Source : in Bounded_String;
From : in Positive;
Going : in Direction := Forward)
return Natural;
47 function Index_Non_Blank (Source : in Bounded_String;
Going : in Direction := Forward)
return Natural;
48 function Count (Source : in Bounded_String;
Pattern : in String;
Mapping : in Maps.Character_Mapping
:= Maps.Identity)
return Natural;
49 function Count (Source : in Bounded_String;
Pattern : in String;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
50 function Count (Source : in Bounded_String;
Set : in Maps.Character_Set)
return Natural;
51 procedure Find_Token (Source : in Bounded_String;
Set : in Maps.Character_Set;
Test : in Membership;
First : out Positive;
Last : out Natural);
52 -- String translation subprograms
53 function Translate (Source : in Bounded_String;
Mapping : in Maps.Character_Mapping)
return Bounded_String;
54 procedure Translate (Source : in out Bounded_String;
Mapping : in Maps.Character_Mapping);
55 function Translate (Source : in Bounded_String;
Mapping : in Maps.Character_Mapping_Function)
return Bounded_String;
56 procedure Translate (Source : in out Bounded_String;
Mapping : in Maps.Character_Mapping_Function);
57 -- String transformation subprograms
58 function Replace_Slice (Source : in Bounded_String;
Low : in Positive;
High : in Natural;
By : in String;
Drop : in Truncation := Error)
return Bounded_String;
59 procedure Replace_Slice (Source : in out Bounded_String;
Low : in Positive;
High : in Natural;
By : in String;
Drop : in Truncation := Error);
60 function Insert (Source : in Bounded_String;
Before : in Positive;
New_Item : in String;
Drop : in Truncation := Error)
return Bounded_String;
61 procedure Insert (Source : in out Bounded_String;
Before : in Positive;
New_Item : in String;
Drop : in Truncation := Error);
62 function Overwrite (Source : in Bounded_String;
Position : in Positive;
New_Item : in String;
Drop : in Truncation := Error)
return Bounded_String;
63 procedure Overwrite (Source : in out Bounded_String;
Position : in Positive;
New_Item : in String;
Drop : in Truncation := Error);
64 function Delete (Source : in Bounded_String;
From : in Positive;
Through : in Natural)
return Bounded_String;
65 procedure Delete (Source : in out Bounded_String;
From : in Positive;
Through : in Natural);
66 --String selector subprograms
67 function Trim (Source : in Bounded_String;
Side : in Trim_End)
return Bounded_String;
procedure Trim (Source : in out Bounded_String;
Side : in Trim_End);
68 function Trim (Source : in Bounded_String;
Left : in Maps.Character_Set;
Right : in Maps.Character_Set)
return Bounded_String;
69 procedure Trim (Source : in out Bounded_String;
Left : in Maps.Character_Set;
Right : in Maps.Character_Set);
70 function Head (Source : in Bounded_String;
Count : in Natural;
Pad : in Character := Space;
Drop : in Truncation := Error)
return Bounded_String;
71 procedure Head (Source : in out Bounded_String;
Count : in Natural;
Pad : in Character := Space;
Drop : in Truncation := Error);
72 function Tail (Source : in Bounded_String;
Count : in Natural;
Pad : in Character := Space;
Drop : in Truncation := Error)
return Bounded_String;
73 procedure Tail (Source : in out Bounded_String;
Count : in Natural;
Pad : in Character := Space;
Drop : in Truncation := Error);
74 --String constructor subprograms
75 function "*" (Left : in Natural;
Right : in Character)
return Bounded_String;
76 function "*" (Left : in Natural;
Right : in String)
return Bounded_String;
77 function "*" (Left : in Natural;
Right : in Bounded_String)
return Bounded_String;
78 function Replicate (Count : in Natural;
Item : in Character;
Drop : in Truncation := Error)
return Bounded_String;
79 function Replicate (Count : in Natural;
Item : in String;
Drop : in Truncation := Error)
return Bounded_String;
80 function Replicate (Count : in Natural;
Item : in Bounded_String;
Drop : in Truncation := Error)
return Bounded_String;
81 private
... -- not specified by the language
end Generic_Bounded_Length;
82 end Ada.Strings.Bounded;
82.a.1/2 This paragraph was deleted.{8652/0097} {AI95-00115-01}
{AI95-00344-01}
83 Null_Bounded_String represents the null string. If an object of type
Bounded_String is not otherwise initialized, it will be initialized to the
same value as Null_Bounded_String.
84 function Length (Source : in Bounded_String) return Length_Range;
85 The Length function returns the length of the string represented
by Source.
86 function To_Bounded_String (Source : in String;
Drop : in Truncation := Error)
return Bounded_String;
87 If Source'Length <= Max_Length then this function returns a
Bounded_String that represents Source. Otherwise the effect
depends on the value of Drop:
88 * If Drop=Left, then the result is a Bounded_String that
represents the string comprising the rightmost Max_Length
characters of Source.
89 * If Drop=Right, then the result is a Bounded_String that
represents the string comprising the leftmost Max_Length
characters of Source.
90 * If Drop=Error, then Strings.Length_Error is propagated.
91 function To_String (Source : in Bounded_String) return String;
92 To_String returns the String value with lower bound 1 represented
by Source. If B is a Bounded_String, then B =
To_Bounded_String(To_String(B)).
92.1/2 procedure Set_Bounded_String
(Target : out Bounded_String;
Source : in String;
Drop : in Truncation := Error);
92.2/2 {AI95-00301-01} Equivalent to Target := To_Bounded_String (Source,
Drop);
93 Each of the Append functions returns a Bounded_String obtained by
concatenating the string or character given or represented by one of the
parameters, with the string or character given or represented by the other
parameter, and applying To_Bounded_String to the concatenation result string,
with Drop as provided to the Append function.
94 Each of the procedures Append(Source, New_Item, Drop) has the same effect
as the corresponding assignment Source := Append(Source, New_Item, Drop).
95 Each of the "&" functions has the same effect as the corresponding Append
function, with Error as the Drop parameter.
96 function Element (Source : in Bounded_String;
Index : in Positive)
return Character;
97 Returns the character at position Index in the string represented
by Source; propagates Index_Error if Index > Length(Source).
98 procedure Replace_Element (Source : in out Bounded_String;
Index : in Positive;
By : in Character);
99 Updates Source such that the character at position Index in the
string represented by Source is By; propagates Index_Error if
Index > Length(Source).
100 function Slice (Source : in Bounded_String;
Low : in Positive;
High : in Natural)
return String;
101/1 {8652/0049} {AI95-00128-01} {AI95-00238-01} Returns the slice at
positions Low through High in the string represented by Source;
propagates Index_Error if Low > Length(Source)+1 or High >
Length(Source). The bounds of the returned string are Low and
High..
101.1/2 function Bounded_Slice
(Source : in Bounded_String;
Low : in Positive;
High : in Natural)
return Bounded_String;
101.2/2 {AI95-00301-01} Returns the slice at positions Low through High in
the string represented by Source as a bounded string; propagates
Index_Error if Low > Length(Source)+1 or High > Length(Source).
101.3/2 procedure Bounded_Slice
(Source : in Bounded_String;
Target : out Bounded_String;
Low : in Positive;
High : in Natural);
101.4/2 {AI95-00301-01} Equivalent to Target := Bounded_Slice (Source,
Low, High);
102 Each of the functions "=", "<", ">", "<=", and ">=" returns the same
result as the corresponding String operation applied to the String values
given or represented by the two parameters.
103 Each of the search subprograms (Index, Index_Non_Blank, Count, Find_Token)
has the same effect as the corresponding subprogram in Strings.Fixed applied
to the string represented by the Bounded_String parameter.
104 Each of the Translate subprograms, when applied to a Bounded_String, has
an analogous effect to the corresponding subprogram in Strings.Fixed. For the
Translate function, the translation is applied to the string represented by
the Bounded_String parameter, and the result is converted (via
To_Bounded_String) to a Bounded_String. For the Translate procedure, the
string represented by the Bounded_String parameter after the translation is
given by the Translate function for fixed-length strings applied to the string
represented by the original value of the parameter.
105/1 {8652/0049} {AI95-00128-01} Each of the transformation subprograms
(Replace_Slice, Insert, Overwrite, Delete), selector subprograms (Trim, Head,
Tail), and constructor functions ("*") has an effect based on its
corresponding subprogram in Strings.Fixed, and Replicate is based on
Fixed."*". In the case of a function, the corresponding fixed-length string
subprogram is applied to the string represented by the Bounded_String
parameter. To_Bounded_String is applied the result string, with Drop (or Error
in the case of Generic_Bounded_Length."*") determining the effect when the
string length exceeds Max_Length. In the case of a procedure, the
corresponding function in Strings.Bounded.Generic_Bounded_Length is applied,
with the result assigned into the Source parameter.
105.a/2 Ramification: {AI95-00114-01} The "/=" operations between
Bounded_String and String, and between String and Bounded_String,
are automatically defined based on the corresponding "="
operations.
Implementation Advice
106 Bounded string objects should not be implemented by implicit pointers and
dynamic allocation.
106.a.1/2 Implementation Advice: Bounded string objects should not be
implemented by implicit pointers and dynamic allocation.
106.a Implementation Note: The following is a possible implementation of
the private part of the package:
106.b type Bounded_String_Internals (Length : Length_Range := 0) is
record
Data : String(1..Length);
end record;
106.c type Bounded_String is
record
Data : Bounded_String_Internals; -- Unconstrained
end record;
106.d Null_Bounded_String : constant Bounded_String :=
(Data => (Length => 0,
Data => (1..0 => ' ')));
Inconsistencies With Ada 95
106.e/2 {AI95-00238-01} {inconsistencies with Ada 95} Amendment
Correction: The bounds of the string returned from Slice are now
defined. This is technically an inconsistency; if a program
depended on some other lower bound for the string returned from
Slice, it could fail when compiled with Ada 2005. Such code is not
portable even between Ada 95 implementations, so it should be very
rare.
Incompatibilities With Ada 95
106.f/2 {AI95-00301-01} {incompatibilities with Ada 95} Procedure
Set_Bounded_String, two Bounded_Slice subprograms, and overloaded
versions of Index and Index_Non_Blank are newly added to
Strings.Bounded. If Strings.Bounded is referenced in a
use_clause, and an entity E with the same defining_identifier as a
new entity in Strings.Bounded is defined in a package that is also
referenced in a use_clause, the entity E may no longer be
use-visible, resulting in errors. This should be rare and is
easily fixed if it does occur.
Wording Changes from Ada 95
106.g/2 {8652/0049} {AI95-00128-01} Corrigendum: Corrected the conditions
for which Slice raises Index_Error.
106.h/2 {8652/0049} {AI95-00128-01} Corrigendum: Clarified the meaning of
transformation, selector, and constructor subprograms by
describing the effects of procedures and functions separately.
A.4.5 Unbounded-Length String Handling
1 The language-defined package Strings.Unbounded provides a private type
Unbounded_String and a set of operations. An object of type Unbounded_String
represents a String whose low bound is 1 and whose length can vary
conceptually between 0 and Natural'Last. The subprograms for fixed-length
string handling are either overloaded directly for Unbounded_String, or are
modified as needed to reflect the flexibility in length. Since the
Unbounded_String type is private, relevant constructor and selector operations
are provided.
1.a Reason: The transformation operations for fixed- and
bounded-length strings that are not necessarily length preserving
are supplied for Unbounded_String as procedures as well as
functions. This allows an implementation to do an initial
allocation for an unbounded string and to avoid further
allocations as long as the length does not exceed the allocated
length.
Static Semantics
2 The library package Strings.Unbounded has the following declaration:
3 with Ada.Strings.Maps;
package Ada.Strings.Unbounded is
pragma Preelaborate(Unbounded);
4/2 {AI95-00161-01} type Unbounded_String is private;
pragma Preelaborable_Initialization(Unbounded_String);
5 Null_Unbounded_String : constant Unbounded_String;
6 function Length (Source : in Unbounded_String) return Natural;
7 type String_Access is access all String;
procedure Free (X : in out String_Access);
8 -- Conversion, Concatenation, and Selection functions
9 function To_Unbounded_String (Source : in String)
return Unbounded_String;
10 function To_Unbounded_String (Length : in Natural)
return Unbounded_String;
11 function To_String (Source : in Unbounded_String) return String;
11.1/2 {AI95-00301-01} procedure Set_Unbounded_String
(Target : out Unbounded_String;
Source : in String);
12 procedure Append (Source : in out Unbounded_String;
New_Item : in Unbounded_String);
13 procedure Append (Source : in out Unbounded_String;
New_Item : in String);
14 procedure Append (Source : in out Unbounded_String;
New_Item : in Character);
15 function "&" (Left, Right : in Unbounded_String)
return Unbounded_String;
16 function "&" (Left : in Unbounded_String; Right : in String)
return Unbounded_String;
17 function "&" (Left : in String; Right : in Unbounded_String)
return Unbounded_String;
18 function "&" (Left : in Unbounded_String; Right : in Character)
return Unbounded_String;
19 function "&" (Left : in Character; Right : in Unbounded_String)
return Unbounded_String;
20 function Element (Source : in Unbounded_String;
Index : in Positive)
return Character;
21 procedure Replace_Element (Source : in out Unbounded_String;
Index : in Positive;
By : in Character);
22 function Slice (Source : in Unbounded_String;
Low : in Positive;
High : in Natural)
return String;
22.1/2 {AI95-00301-01} function Unbounded_Slice
(Source : in Unbounded_String;
Low : in Positive;
High : in Natural)
return Unbounded_String;
22.2/2 {AI95-00301-01} procedure Unbounded_Slice
(Source : in Unbounded_String;
Target : out Unbounded_String;
Low : in Positive;
High : in Natural);
23 function "=" (Left, Right : in Unbounded_String) return Boolean;
24 function "=" (Left : in Unbounded_String; Right : in String)
return Boolean;
25 function "=" (Left : in String; Right : in Unbounded_String)
return Boolean;
26 function "<" (Left, Right : in Unbounded_String) return Boolean;
27 function "<" (Left : in Unbounded_String; Right : in String)
return Boolean;
28 function "<" (Left : in String; Right : in Unbounded_String)
return Boolean;
29 function "<=" (Left, Right : in Unbounded_String) return Boolean;
30 function "<=" (Left : in Unbounded_String; Right : in String)
return Boolean;
31 function "<=" (Left : in String; Right : in Unbounded_String)
return Boolean;
32 function ">" (Left, Right : in Unbounded_String) return Boolean;
33 function ">" (Left : in Unbounded_String; Right : in String)
return Boolean;
34 function ">" (Left : in String; Right : in Unbounded_String)
return Boolean;
35 function ">=" (Left, Right : in Unbounded_String) return Boolean;
36 function ">=" (Left : in Unbounded_String; Right : in String)
return Boolean;
37 function ">=" (Left : in String; Right : in Unbounded_String)
return Boolean;
38 -- Search subprograms
38.1/2 {AI95-00301-01} function Index (Source : in Unbounded_String;
Pattern : in String;
From : in Positive;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping := Maps.Identity)
return Natural;
38.2/2 {AI95-00301-01} function Index (Source : in Unbounded_String;
Pattern : in String;
From : in Positive;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
39 function Index (Source : in Unbounded_String;
Pattern : in String;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping
:= Maps.Identity)
return Natural;
40 function Index (Source : in Unbounded_String;
Pattern : in String;
Going : in Direction := Forward;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
40.1/2 {AI95-00301-01} function Index (Source : in Unbounded_String;
Set : in Maps.Character_Set;
From : in Positive;
Test : in Membership := Inside;
Going : in Direction := Forward)
return Natural;
41 function Index (Source : in Unbounded_String;
Set : in Maps.Character_Set;
Test : in Membership := Inside;
Going : in Direction := Forward) return Natural;
41.1/2 {AI95-00301-01} function Index_Non_Blank
(Source : in Unbounded_String;
From : in Positive;
Going : in Direction := Forward)
return Natural;
42 function Index_Non_Blank (Source : in Unbounded_String;
Going : in Direction := Forward)
return Natural;
43 function Count (Source : in Unbounded_String;
Pattern : in String;
Mapping : in Maps.Character_Mapping
:= Maps.Identity)
return Natural;
44 function Count (Source : in Unbounded_String;
Pattern : in String;
Mapping : in Maps.Character_Mapping_Function)
return Natural;
45 function Count (Source : in Unbounded_String;
Set : in Maps.Character_Set)
return Natural;
46 procedure Find_Token (Source : in Unbounded_String;
Set : in Maps.Character_Set;
Test : in Membership;
First : out Positive;
Last : out Natural);
47 -- String translation subprograms
48 function Translate (Source : in Unbounded_String;
Mapping : in Maps.Character_Mapping)
return Unbounded_String;
49 procedure Translate (Source : in out Unbounded_String;
Mapping : in Maps.Character_Mapping);
50 function Translate (Source : in Unbounded_String;
Mapping : in Maps.Character_Mapping_Function)
return Unbounded_String;
51 procedure Translate (Source : in out Unbounded_String;
Mapping : in Maps.Character_Mapping_Function);
52 -- String transformation subprograms
53 function Replace_Slice (Source : in Unbounded_String;
Low : in Positive;
High : in Natural;
By : in String)
return Unbounded_String;
54 procedure Replace_Slice (Source : in out Unbounded_String;
Low : in Positive;
High : in Natural;
By : in String);
55 function Insert (Source : in Unbounded_String;
Before : in Positive;
New_Item : in String)
return Unbounded_String;
56 procedure Insert (Source : in out Unbounded_String;
Before : in Positive;
New_Item : in String);
57 function Overwrite (Source : in Unbounded_String;
Position : in Positive;
New_Item : in String)
return Unbounded_String;
58 procedure Overwrite (Source : in out Unbounded_String;
Position : in Positive;
New_Item : in String);
59 function Delete (Source : in Unbounded_String;
From : in Positive;
Through : in Natural)
return Unbounded_String;
60 procedure Delete (Source : in out Unbounded_String;
From : in Positive;
Through : in Natural);
61 function Trim (Source : in Unbounded_String;
Side : in Trim_End)
return Unbounded_String;
62 procedure Trim (Source : in out Unbounded_String;
Side : in Trim_End);
63 function Trim (Source : in Unbounded_String;
Left : in Maps.Character_Set;
Right : in Maps.Character_Set)
return Unbounded_String;
64 procedure Trim (Source : in out Unbounded_String;
Left : in Maps.Character_Set;
Right : in Maps.Character_Set);
65 function Head (Source : in Unbounded_String;
Count : in Natural;
Pad : in Character := Space)
return Unbounded_String;
66 procedure Head (Source : in out Unbounded_String;
Count : in Natural;
Pad : in Character := Space);
67 function Tail (Source : in Unbounded_String;
Count : in Natural;
Pad : in Character := Space)
return Unbounded_String;
68 procedure Tail (Source : in out Unbounded_String;
Count : in Natural;
Pad : in Character := Space);
69 function "*" (Left : in Natural;
Right : in Character)
return Unbounded_String;
70 function "*" (Left : in Natural;
Right : in String)
return Unbounded_String;
71 function "*" (Left : in Natural;
Right : in Unbounded_String)
return Unbounded_String;
72 private
... -- not specified by the language
end Ada.Strings.Unbounded;
72.1/2 {AI95-00360-01} The type Unbounded_String needs finalization (see 7.6).
73 Null_Unbounded_String represents the null String. If an object of type
Unbounded_String is not otherwise initialized, it will be initialized to the
same value as Null_Unbounded_String.
74 The function Length returns the length of the String represented by Source.
75 The type String_Access provides a (non-private) access type for explicit
processing of unbounded-length strings. The procedure Free performs an
unchecked deallocation of an object of type String_Access.
76 The function To_Unbounded_String(Source : in String) returns an
Unbounded_String that represents Source. The function
To_Unbounded_String(Length : in Natural) returns an Unbounded_String that
represents an uninitialized String whose length is Length.
77 The function To_String returns the String with lower bound 1 represented
by Source. To_String and To_Unbounded_String are related as follows:
78 * If S is a String, then To_String(To_Unbounded_String(S)) = S.
79 * If U is an Unbounded_String, then To_Unbounded_String(To_String(U)) =
U.
79.1/2 {AI95-00301-01} The procedure Set_Unbounded_String sets Target to an
Unbounded_String that represents Source.
80 For each of the Append procedures, the resulting string represented by the
Source parameter is given by the concatenation of the original value of Source
and the value of New_Item.
81 Each of the "&" functions returns an Unbounded_String obtained by
concatenating the string or character given or represented by one of the
parameters, with the string or character given or represented by the other
parameter, and applying To_Unbounded_String to the concatenation result string.
82 The Element, Replace_Element, and Slice subprograms have the same effect
as the corresponding bounded-length string subprograms.
82.1/2 {AI95-00301-01} The function Unbounded_Slice returns the slice at
positions Low through High in the string represented by Source as an
Unbounded_String. The procedure Unbounded_Slice sets Target to the
Unbounded_String representing the slice at positions Low through High in the
string represented by Source. Both routines propagate Index_Error if Low >
Length(Source)+1 or High > Length(Source).
83 Each of the functions "=", "<", ">", "<=", and ">=" returns the same
result as the corresponding String operation applied to the String values
given or represented by Left and Right.
84 Each of the search subprograms (Index, Index_Non_Blank, Count, Find_Token)
has the same effect as the corresponding subprogram in Strings.Fixed applied
to the string represented by the Unbounded_String parameter.
85 The Translate function has an analogous effect to the corresponding
subprogram in Strings.Fixed. The translation is applied to the string
represented by the Unbounded_String parameter, and the result is converted
(via To_Unbounded_String) to an Unbounded_String.
86 Each of the transformation functions (Replace_Slice, Insert, Overwrite,
Delete), selector functions (Trim, Head, Tail), and constructor functions
("*") is likewise analogous to its corresponding subprogram in Strings.Fixed.
For each of the subprograms, the corresponding fixed-length string subprogram
is applied to the string represented by the Unbounded_String parameter, and
To_Unbounded_String is applied the result string.
87 For each of the procedures Translate, Replace_Slice, Insert, Overwrite,
Delete, Trim, Head, and Tail, the resulting string represented by the Source
parameter is given by the corresponding function for fixed-length strings
applied to the string represented by Source's original value.
Implementation Requirements
88 No storage associated with an Unbounded_String object shall be lost upon
assignment or scope exit.
88.a/2 Implementation Note: {AI95-00301-01} A sample implementation of
the private part of the package and several of the subprograms
appears in the Ada 95 Rationale.
Incompatibilities With Ada 95
88.b/2 {AI95-00360-01} {incompatibilities with Ada 95} Amendment
Correction: Type Unbounded_String is defined to need finalization.
If the restriction No_Nested_Finalization (see D.7) applies to the
partition, and Unbounded_String does not have a controlled part,
it will not be allowed in local objects in Ada 2005 whereas it
would be allowed in original Ada 95. Such code is not portable, as
most Ada compilers have a controlled part in Unbounded_String, and
thus would be illegal.
88.c/2 {AI95-00301-01} Procedure Set_Unbounded_String, two
Unbounded_Slice subprograms, and overloaded versions of Index and
Index_Non_Blank are newly added to Strings.Unbounded. If
Strings.Unbounded is referenced in a use_clause, and an entity E
with the same defining_identifier as a new entity in
Strings.Unbounded is defined in a package that is also referenced
in a use_clause, the entity E may no longer be use-visible,
resulting in errors. This should be rare and is easily fixed if it
does occur.
Extensions to Ada 95
88.d/2 {AI95-00161-01} {extensions to Ada 95} Amendment Correction: Added
a pragma Preelaborable_Initialization to type Unbounded_String, so
that it can be used to declare default-initialized objects in
preelaborated units.
A.4.6 String-Handling Sets and Mappings
1 The language-defined package Strings.Maps.Constants declares Character_Set
and Character_Mapping constants corresponding to classification and conversion
functions in package Characters.Handling.
1.a Discussion: The Constants package is a child of Strings.Maps since
it needs visibility of the private part of Strings.Maps in order
to initialize the constants in a preelaborable way (i.e. via
aggregates versus function calls).
Static Semantics
2 The library package Strings.Maps.Constants has the following declaration:
3/2 {AI95-00362-01} package Ada.Strings.Maps.Constants is
pragma Pure(Constants);
4 Control_Set : constant Character_Set;
Graphic_Set : constant Character_Set;
Letter_Set : constant Character_Set;
Lower_Set : constant Character_Set;
Upper_Set : constant Character_Set;
Basic_Set : constant Character_Set;
Decimal_Digit_Set : constant Character_Set;
Hexadecimal_Digit_Set : constant Character_Set;
Alphanumeric_Set : constant Character_Set;
Special_Set : constant Character_Set;
ISO_646_Set : constant Character_Set;
5 Lower_Case_Map : constant Character_Mapping;
--Maps to lower case for letters, else identity
Upper_Case_Map : constant Character_Mapping;
--Maps to upper case for letters, else identity
Basic_Map : constant Character_Mapping;
--Maps to basic letter for letters, else identity
6 private
... -- not specified by the language
end Ada.Strings.Maps.Constants;
7 Each of these constants represents a correspondingly named set of
characters or character mapping in Characters.Handling (see A.3.2).
Extensions to Ada 95
7.a/2 {AI95-00362-01} {extensions to Ada 95} Strings.Maps.Constants is
now Pure, so it can be used in pure units.
A.4.7 Wide_String Handling
1/2 {AI95-00302-03} Facilities for handling strings of Wide_Character elements
are found in the packages Strings.Wide_Maps, Strings.Wide_Fixed, Strings.-
Wide_Bounded, Strings.Wide_Unbounded, and Strings.Wide_Maps.Wide_Constants,
and in the functions Strings.Wide_Hash, Strings.Wide_Fixed.Wide_Hash, Strings.-
Wide_Bounded.Wide_Hash, and Strings.Wide_Unbounded.Wide_Hash. They provide the
same string-handling operations as the corresponding packages and functions
for strings of Character elements.
Static Semantics
2 The package Strings.Wide_Maps has the following declaration.
3 package Ada.Strings.Wide_Maps is
pragma Preelaborate(Wide_Maps);
4/2 {AI95-00161-01}
-- Representation for a set of Wide_Character values:
type Wide_Character_Set is private;
pragma Preelaborable_Initialization(Wide_Character_Set);
5 Null_Set : constant Wide_Character_Set;
6 type Wide_Character_Range is
record
Low : Wide_Character;
High : Wide_Character;
end record;
-- Represents Wide_Character range Low..High
7 type Wide_Character_Ranges is array (Positive range <>)
of Wide_Character_Range;
8 function To_Set (Ranges : in Wide_Character_Ranges)
return Wide_Character_Set;
9 function To_Set (Span : in Wide_Character_Range)
return Wide_Character_Set;
10 function To_Ranges (Set : in Wide_Character_Set)
return Wide_Character_Ranges;
11 function "=" (Left, Right : in Wide_Character_Set) return Boolean;
12 function "not" (Right : in Wide_Character_Set)
return Wide_Character_Set;
function "and" (Left, Right : in Wide_Character_Set)
return Wide_Character_Set;
function "or" (Left, Right : in Wide_Character_Set)
return Wide_Character_Set;
function "xor" (Left, Right : in Wide_Character_Set)
return Wide_Character_Set;
function "-" (Left, Right : in Wide_Character_Set)
return Wide_Character_Set;
13 function Is_In (Element : in Wide_Character;
Set : in Wide_Character_Set)
return Boolean;
14 function Is_Subset (Elements : in Wide_Character_Set;
Set : in Wide_Character_Set)
return Boolean;
15 function "<=" (Left : in Wide_Character_Set;
Right : in Wide_Character_Set)
return Boolean renames Is_Subset;
16 -- Alternative representation for a set of Wide_Character values:
subtype Wide_Character_Sequence is Wide_String;
17 function To_Set (Sequence : in Wide_Character_Sequence)
return Wide_Character_Set;
18 function To_Set (Singleton : in Wide_Character)
return Wide_Character_Set;
19 function To_Sequence (Set : in Wide_Character_Set)
return Wide_Character_Sequence;
20/2 {AI95-00161-01}
-- Representation for a Wide_Character to Wide_Character mapping:
type Wide_Character_Mapping is private;
pragma Preelaborable_Initialization(Wide_Character_Mapping);
21 function Value (Map : in Wide_Character_Mapping;
Element : in Wide_Character)
return Wide_Character;
22 Identity : constant Wide_Character_Mapping;
23 function To_Mapping (From, To : in Wide_Character_Sequence)
return Wide_Character_Mapping;
24 function To_Domain (Map : in Wide_Character_Mapping)
return Wide_Character_Sequence;
25 function To_Range (Map : in Wide_Character_Mapping)
return Wide_Character_Sequence;
26 type Wide_Character_Mapping_Function is
access function (From : in Wide_Character) return Wide_Character;
27 private
... -- not specified by the language
end Ada.Strings.Wide_Maps;
28 The context clause for each of the packages Strings.Wide_Fixed,
Strings.Wide_Bounded, and Strings.Wide_Unbounded identifies Strings.Wide_Maps
instead of Strings.Maps.
29/2 {AI95-00302-03} For each of the packages Strings.Fixed, Strings.Bounded,
Strings.Unbounded, and Strings.Maps.Constants, and for functions Strings.Hash,
Strings.Fixed.Hash, Strings.Bounded.Hash, and Strings.Unbounded.Hash, the
corresponding wide string package has the same contents except that
30 * Wide_Space replaces Space
31 * Wide_Character replaces Character
32 * Wide_String replaces String
33 * Wide_Character_Set replaces Character_Set
34 * Wide_Character_Mapping replaces Character_Mapping
35 * Wide_Character_Mapping_Function replaces Character_Mapping_Function
36 * Wide_Maps replaces Maps
37 * Bounded_Wide_String replaces Bounded_String
38 * Null_Bounded_Wide_String replaces Null_Bounded_String
39 * To_Bounded_Wide_String replaces To_Bounded_String
40 * To_Wide_String replaces To_String
40.1/2 * {AI95-00301-01} Set_Bounded_Wide_String replaces Set_Bounded_String
41 * Unbounded_Wide_String replaces Unbounded_String
42 * Null_Unbounded_Wide_String replaces Null_Unbounded_String
43 * Wide_String_Access replaces String_Access
44 * To_Unbounded_Wide_String replaces To_Unbounded_String
44.1/2 * {AI95-00301-01} Set_Unbounded_Wide_String replaces
Set_Unbounded_String
45 The following additional declaration is present in
Strings.Wide_Maps.Wide_Constants:
46/2 {AI95-00285-01} {AI95-00395-01} Character_Set
: constant Wide_Maps.Wide_Character_Set;
--Contains each Wide_Character value WC such that
--Characters.Conversions.Is_Character(WC) is True
46.1/2 {AI95-00395-01} Each Wide_Character_Set constant in the package
Strings.Wide_Maps.Wide_Constants contains no values outside the Character
portion of Wide_Character. Similarly, each Wide_Character_Mapping constant in
this package is the identity mapping when applied to any element outside the
Character portion of Wide_Character.
46.2/2 {AI95-00362-01} Pragma Pure is replaced by pragma Preelaborate in
Strings.Wide_Maps.Wide_Constants.
NOTES
47 12 {Constraint_Error (raised by failure of run-time check)} If a null
Wide_Character_Mapping_Function is passed to any of the Wide_String
handling subprograms, Constraint_Error is propagated.
48/2 This paragraph was deleted.{AI95-00395-01}
Incompatibilities With Ada 95
48.a/2 {AI95-00301-01} {incompatibilities with Ada 95} Various new
operations are added to Strings.Wide_Fixed, Strings.Wide_Bounded,
and Strings.Wide_Unbounded. If one of these packages is referenced
in a use_clause, and an entity E with the same
defining_identifier as a new entity is defined in a package that
is also referenced in a use_clause, the entity E may no longer be
use-visible, resulting in errors. This should be rare and is
easily fixed if it does occur.
Extensions to Ada 95
48.b/2 {AI95-00161-01} {extensions to Ada 95} Amendment Correction: Added
pragma Preelaborable_Initialization to types Wide_Character_Set
and Wide_Character_Mapping, so that they can be used to declare
default-initialized objects in preelaborated units.
Wording Changes from Ada 95
48.c/2 {AI95-00285-01} Corrected the description of Character_Set.
48.d/2 {AI95-00302-03} Added wide versions of Strings.Hash and
Strings.Unbounded.Hash.
48.e/2 {AI95-00362-01} Added wording so that
Strings.Wide_Maps.Wide_Constants does not change to Pure.
48.f/2 {AI95-00395-01} The second Note is now normative text, since there
is no way to derive it from the other rules. It's a little weird
given the use of Unicode character classifications in Ada 2005;
but changing it would be inconsistent with Ada 95 and a one-to-one
mapping isn't necessarily correct anyway.
A.4.8 Wide_Wide_String Handling
1/2 {AI95-00285-01} {AI95-00395-01} Facilities for handling strings of
Wide_Wide_Character elements are found in the packages Strings.Wide_Wide_-
Maps, Strings.Wide_Wide_Fixed, Strings.Wide_Wide_Bounded, Strings.Wide_Wide_-
Unbounded, and Strings.Wide_Wide_Maps.Wide_Wide_Constants, and in the
functions Strings.Wide_Wide_Hash, Strings.Wide_Wide_Fixed.Wide_Wide_Hash,
Strings.Wide_Wide_Bounded.Wide_Wide_Hash, and Strings.Wide_Wide_Unbounded.-
Wide_Wide_Hash. They provide the same string-handling operations as the
corresponding packages and functions for strings of Character elements.
Static Semantics
2/2 {AI95-00285-01} The library package Strings.Wide_Wide_Maps has the
following declaration.
3/2 package Ada.Strings.Wide_Wide_Maps is
pragma Preelaborate(Wide_Wide_Maps);
4/2 -- Representation for a set of Wide_Wide_Character values:
type Wide_Wide_Character_Set is private;
pragma Preelaborable_Initialization(Wide_Wide_Character_Set);
5/2 Null_Set : constant Wide_Wide_Character_Set;
6/2 type Wide_Wide_Character_Range is
record
Low : Wide_Wide_Character;
High : Wide_Wide_Character;
end record;
-- Represents Wide_Wide_Character range Low..High
7/2 type Wide_Wide_Character_Ranges is array (Positive range <>)
of Wide_Wide_Character_Range;
8/2 function To_Set (Ranges : in Wide_Wide_Character_Ranges)
return Wide_Wide_Character_Set;
9/2 function To_Set (Span : in Wide_Wide_Character_Range)
return Wide_Wide_Character_Set;
10/2 function To_Ranges (Set : in Wide_Wide_Character_Set)
return Wide_Wide_Character_Ranges;
11/2 function "=" (Left, Right : in Wide_Wide_Character_Set) return Boolean;
12/2 function "not" (Right : in Wide_Wide_Character_Set)
return Wide_Wide_Character_Set;
function "and" (Left, Right : in Wide_Wide_Character_Set)
return Wide_Wide_Character_Set;
function "or" (Left, Right : in Wide_Wide_Character_Set)
return Wide_Wide_Character_Set;
function "xor" (Left, Right : in Wide_Wide_Character_Set)
return Wide_Wide_Character_Set;
function "-" (Left, Right : in Wide_Wide_Character_Set)
return Wide_Wide_Character_Set;
13/2 function Is_In (Element : in Wide_Wide_Character;
Set : in Wide_Wide_Character_Set)
return Boolean;
14/2 function Is_Subset (Elements : in Wide_Wide_Character_Set;
Set : in Wide_Wide_Character_Set)
return Boolean;
15/2 function "<=" (Left : in Wide_Wide_Character_Set;
Right : in Wide_Wide_Character_Set)
return Boolean renames Is_Subset;
16/2 -- Alternative representation for a set of Wide_Wide_Character values:
subtype Wide_Wide_Character_Sequence is Wide_Wide_String;
17/2 function To_Set (Sequence : in Wide_Wide_Character_Sequence)
return Wide_Wide_Character_Set;
18/2 function To_Set (Singleton : in Wide_Wide_Character)
return Wide_Wide_Character_Set;
19/2 function To_Sequence (Set : in Wide_Wide_Character_Set)
return Wide_Wide_Character_Sequence;
20/2 -- Representation for a Wide_Wide_Character to Wide_Wide_Character
-- mapping:
type Wide_Wide_Character_Mapping is private;
pragma Preelaborable_Initialization(Wide_Wide_Character_Mapping);
21/2 function Value (Map : in Wide_Wide_Character_Mapping;
Element : in Wide_Wide_Character)
return Wide_Wide_Character;
22/2 Identity : constant Wide_Wide_Character_Mapping;
23/2 function To_Mapping (From, To : in Wide_Wide_Character_Sequence)
return Wide_Wide_Character_Mapping;
24/2 function To_Domain (Map : in Wide_Wide_Character_Mapping)
return Wide_Wide_Character_Sequence;
25/2 function To_Range (Map : in Wide_Wide_Character_Mapping)
return Wide_Wide_Character_Sequence;
26/2 type Wide_Wide_Character_Mapping_Function is
access function (From : in Wide_Wide_Character)
return Wide_Wide_Character;
27/2 private
... -- not specified by the language
end Ada.Strings.Wide_Wide_Maps;
28/2 {AI95-00285-01} The context clause for each of the packages
Strings.Wide_Wide_Fixed, Strings.Wide_Wide_Bounded, and
Strings.Wide_Wide_Unbounded identifies Strings.Wide_Wide_Maps instead of
Strings.Maps.
29/2 {AI95-00285-01} For each of the packages Strings.Fixed, Strings.Bounded,
Strings.Unbounded, and Strings.Maps.Constants, and for functions Strings.-
Hash, Strings.Fixed.Hash, Strings.Bounded.Hash, and Strings.Unbounded.Hash,
the corresponding wide wide string package or function has the same contents
except that
30/2 * Wide_Wide_Space replaces Space
31/2 * Wide_Wide_Character replaces Character
32/2 * Wide_Wide_String replaces String
33/2 * Wide_Wide_Character_Set replaces Character_Set
34/2 * Wide_Wide_Character_Mapping replaces Character_Mapping
35/2 * Wide_Wide_Character_Mapping_Function replaces
Character_Mapping_Function
36/2 * Wide_Wide_Maps replaces Maps
37/2 * Bounded_Wide_Wide_String replaces Bounded_String
38/2 * Null_Bounded_Wide_Wide_String replaces Null_Bounded_String
39/2 * To_Bounded_Wide_Wide_String replaces To_Bounded_String
40/2 * To_Wide_Wide_String replaces To_String
41/2 * {AI95-00301-01} Set_Bounded_Wide_Wide_String replaces
Set_Bounded_String
42/2 * Unbounded_Wide_Wide_String replaces Unbounded_String
43/2 * Null_Unbounded_Wide_Wide_String replaces Null_Unbounded_String
44/2 * Wide_Wide_String_Access replaces String_Access
45/2 * To_Unbounded_Wide_Wide_String replaces To_Unbounded_String
46/2 * {AI95-00301-01} Set_Unbounded_Wide_Wide_String replaces
Set_Unbounded_String
47/2 {AI95-00285-01} {AI95-00395-01} The following additional declarations are
present in Strings.Wide_Wide_Maps.Wide_Wide_Constants:
48/2 Character_Set : constant Wide_Wide_Maps.Wide_Wide_Character_Set;
-- Contains each Wide_Wide_Character value WWC such that
-- Characters.Conversions.Is_Character(WWC) is True
Wide_Character_Set : constant Wide_Wide_Maps.Wide_Wide_Character_Set;
-- Contains each Wide_Wide_Character value WWC such that
-- Characters.Conversions.Is_Wide_Character(WWC) is True
49/2 {AI95-00395-01} Each Wide_Wide_Character_Set constant in the package
Strings.Wide_Wide_Maps.Wide_Wide_Constants contains no values outside the
Character portion of Wide_Wide_Character. Similarly, each Wide_Wide_Character_-
Mapping constant in this package is the identity mapping when applied to any
element outside the Character portion of Wide_Wide_Character.
50/2 {AI95-00395-01} Pragma Pure is replaced by pragma Preelaborate in
Strings.Wide_Wide_Maps.Wide_Wide_Constants.
NOTES
51/2 13 {AI95-00285-01}
{Constraint_Error (raised by failure of run-time check)} If a null
Wide_Wide_Character_Mapping_Function is passed to any of the
Wide_Wide_String handling subprograms, Constraint_Error is propagated.
Extensions to Ada 95
51.a/2 {AI95-00285-01} {AI95-00395-01} {extensions to Ada 95} The
double-wide string-handling packages (Strings.Wide_Wide_Maps,
Strings.Wide_Wide_Fixed, Strings.Wide_Wide_Bounded,
Strings.Wide_Wide_Unbounded, and
Strings.Wide_Wide_Maps.Wide_Wide_Constants), and functions
Strings.Wide_Wide_Hash and
Strings.Wide_Wide_Unbounded.Wide_Wide_Hash are new.
A.4.9 String Hashing
Static Semantics
1/2 {AI95-00302-03} The library function Strings.Hash has the following
declaration:
2/2 with Ada.Containers;
function Ada.Strings.Hash (Key : String) return Containers.Hash_Type;
pragma Pure(Hash);
3/2 Returns an implementation-defined value which is a function of the
value of Key. If A and B are strings such that A equals B, Hash(A)
equals Hash(B).
3.a/2 Implementation defined: The values returned by Strings.Hash.
4/2 {AI95-00302-03} The library function Strings.Fixed.Hash has the following
declaration:
5/2 with Ada.Containers, Ada.Strings.Hash;
function Ada.Strings.Fixed.Hash (Key : String) return Containers.Hash_Type
renames Ada.Strings.Hash;
pragma Pure(Hash);
6/2 {AI95-00302-03} The generic library function Strings.Bounded.Hash has the
following declaration:
7/2 with Ada.Containers;
generic
with package Bounded is
new Ada.Strings.Bounded.Generic_Bounded_Length (<>);
function Ada.Strings.Bounded.Hash (Key : Bounded.Bounded_String)
return Containers.Hash_Type;
pragma Preelaborate(Hash);
8/2 Strings.Bounded.Hash is equivalent to the function call
Strings.Hash (Bounded.To_String (Key));
9/2 {AI95-00302-03} The library function Strings.Unbounded.Hash has the
following declaration:
10/2 with Ada.Containers;
function Ada.Strings.Unbounded.Hash (Key : Unbounded_String)
return Containers.Hash_Type;
pragma Preelaborate(Hash);
11/2 Strings.Unbounded.Hash is equivalent to the function call
Strings.Hash (To_String (Key));
Implementation Advice
12/2 {AI95-00302-03} The Hash functions should be good hash functions,
returning a wide spread of values for different string values. It should be
unlikely for similar strings to return the same value.
12.a/2 Implementation Advice: Strings.Hash should be good a hash
function, returning a wide spread of values for different string
values, and similar strings should rarely return the same value.
12.b/2 Ramification: The other functions are defined in terms of
Strings.Hash, so they don't need separate advice in the Annex.
Extensions to Ada 95
12.c/2 {AI95-00302-03} {extensions to Ada 95} The Strings.Hash,
Strings.Fixed.Hash, Strings.Bounded.Hash, and
Strings.Unbounded.Hash functions are new.
A.5 The Numerics Packages
1 The library package Numerics is the parent of several child units that
provide facilities for mathematical computation. One child, the generic
package Generic_Elementary_Functions, is defined in A.5.1, together with
nongeneric equivalents; two others, the package Float_Random and the generic
package Discrete_Random, are defined in A.5.2. Additional (optional) children
are defined in Annex G, "Numerics".
Static Semantics
2/1 This paragraph was deleted.
3/2 {AI95-00388-01} package Ada.Numerics is
pragma Pure(Numerics);
Argument_Error : exception;
Pi : constant :=
3.14159_26535_89793_23846_26433_83279_50288_41971_69399_37511;
PI : constant := Pi;
e : constant :=
2.71828_18284_59045_23536_02874_71352_66249_77572_47093_69996;
end Ada.Numerics;
4 The Argument_Error exception is raised by a subprogram in a child unit of
Numerics to signal that one or more of the actual subprogram parameters are
outside the domain of the corresponding mathematical function.
Implementation Permissions
5 The implementation may specify the values of Pi and e to a larger number
of significant digits.
5.a Reason: 51 digits seem more than adequate for all present
computers; converted to binary, the values given above are
accurate to more than 160 bits. Nevertheless, the permission
allows implementations to accommodate unforeseen hardware
advances.
Extensions to Ada 83
5.b {extensions to Ada 83} Numerics and its children were not
predefined in Ada 83.
Extensions to Ada 95
5.c/2 {AI95-00388-01} {extensions to Ada 95} The alternative declaration
of PI is new.
A.5.1 Elementary Functions
1 Implementation-defined approximations to the mathematical functions known
as the "elementary functions" are provided by the subprograms in Numerics.-
Generic_Elementary_Functions. Nongeneric equivalents of this generic package
for each of the predefined floating point types are also provided as children
of Numerics.
1.a Implementation defined: The accuracy actually achieved by the
elementary functions.
Static Semantics
2 The generic library package Numerics.Generic_Elementary_Functions has the
following declaration:
3 generic
type Float_Type is digits <>;
package Ada.Numerics.Generic_Elementary_Functions is
pragma Pure(Generic_Elementary_Functions);
4 function Sqrt
(X : Float_Type'Base) return Float_Type'Base;
function Log
(X : Float_Type'Base) return Float_Type'Base;
function Log
(X, Base : Float_Type'Base) return Float_Type'Base;
function Exp
(X : Float_Type'Base) return Float_Type'Base;
function "**" (Left, Right : Float_Type'Base) return Float_Type'Base;
5 function Sin
(X : Float_Type'Base) return Float_Type'Base;
function Sin
(X, Cycle : Float_Type'Base) return Float_Type'Base;
function Cos
(X : Float_Type'Base) return Float_Type'Base;
function Cos
(X, Cycle : Float_Type'Base) return Float_Type'Base;
function Tan
(X : Float_Type'Base) return Float_Type'Base;
function Tan
(X, Cycle : Float_Type'Base) return Float_Type'Base;
function Cot
(X : Float_Type'Base) return Float_Type'Base;
function Cot
(X, Cycle : Float_Type'Base) return Float_Type'Base;
6 function Arcsin
(X : Float_Type'Base) return Float_Type'Base;
function Arcsin
(X, Cycle : Float_Type'Base) return Float_Type'Base;
function Arccos
(X : Float_Type'Base) return Float_Type'Base;
function Arccos
(X, Cycle : Float_Type'Base) return Float_Type'Base;
function Arctan (Y : Float_Type'Base;
X : Float_Type'Base := 1.0)
return Float_Type'Base;
function Arctan (Y : Float_Type'Base;
X : Float_Type'Base := 1.0;
Cycle : Float_Type'Base) return Float_Type'Base;
function Arccot (X : Float_Type'Base;
Y : Float_Type'Base := 1.0)
return Float_Type'Base;
function Arccot (X : Float_Type'Base;
Y : Float_Type'Base := 1.0;
Cycle : Float_Type'Base) return Float_Type'Base;
7 function Sinh
(X : Float_Type'Base) return Float_Type'Base;
function Cosh
(X : Float_Type'Base) return Float_Type'Base;
function Tanh
(X : Float_Type'Base) return Float_Type'Base;
function Coth
(X : Float_Type'Base) return Float_Type'Base;
function Arcsinh
(X : Float_Type'Base) return Float_Type'Base;
function Arccosh
(X : Float_Type'Base) return Float_Type'Base;
function Arctanh
(X : Float_Type'Base) return Float_Type'Base;
function Arccoth
(X : Float_Type'Base) return Float_Type'Base;
8 end Ada.Numerics.Generic_Elementary_Functions;
9/1 {8652/0020} {AI95-00126-01} The library package
Numerics.Elementary_Functions is declared pure and defines the same
subprograms as Numerics.Generic_Elementary_Functions, except that the
predefined type Float is systematically substituted for Float_Type'Base
throughout. Nongeneric equivalents of Numerics.Generic_Elementary_Functions
for each of the other predefined floating point types are defined similarly,
with the names Numerics.Short_Elementary_Functions, Numerics.Long_Elementary_-
Functions, etc.
9.a Reason: The nongeneric equivalents are provided to allow the
programmer to construct simple mathematical applications without
being required to understand and use generics.
10 The functions have their usual mathematical meanings. When the Base
parameter is specified, the Log function computes the logarithm to the given
base; otherwise, it computes the natural logarithm. When the Cycle parameter
is specified, the parameter X of the forward trigonometric functions (Sin,
Cos, Tan, and Cot) and the results of the inverse trigonometric functions
(Arcsin, Arccos, Arctan, and Arccot) are measured in units such that a full
cycle of revolution has the given value; otherwise, they are measured in
radians.
11 The computed results of the mathematically multivalued functions are
rendered single-valued by the following conventions, which are meant to imply
the principal branch:
12 * The results of the Sqrt and Arccosh functions and that of the
exponentiation operator are nonnegative.
13 * The result of the Arcsin function is in the quadrant containing the
point (1.0, x), where x is the value of the parameter X. This quadrant
is I or IV; thus, the range of the Arcsin function is approximately
-PI/2.0 to PI/2.0 (-Cycle/4.0 to Cycle/4.0, if the parameter Cycle is
specified).
14 * The result of the Arccos function is in the quadrant containing the
point (x, 1.0), where x is the value of the parameter X. This quadrant
is I or II; thus, the Arccos function ranges from 0.0 to approximately
PI (Cycle/2.0, if the parameter Cycle is specified).
15 * The results of the Arctan and Arccot functions are in the quadrant
containing the point (x, y), where x and y are the values of the
parameters X and Y, respectively. This may be any quadrant (I through
IV) when the parameter X (resp., Y) of Arctan (resp., Arccot) is
specified, but it is restricted to quadrants I and IV (resp., I and
II) when that parameter is omitted. Thus, the range when that
parameter is specified is approximately -PI to PI (-Cycle/2.0 to
Cycle/2.0, if the parameter Cycle is specified); when omitted, the
range of Arctan (resp., Arccot) is that of Arcsin (resp., Arccos), as
given above. When the point (x, y) lies on the negative x-axis, the
result approximates
16 * PI (resp., -PI) when the sign of the parameter Y is positive
(resp., negative), if Float_Type'Signed_Zeros is True;
17 * PI, if Float_Type'Signed_Zeros is False.
18 (In the case of the inverse trigonometric functions, in which a result
lying on or near one of the axes may not be exactly representable, the
approximation inherent in computing the result may place it in an adjacent
quadrant, close to but on the wrong side of the axis.)
Dynamic Semantics
19 The exception Numerics.Argument_Error is raised, signaling a parameter
value outside the domain of the corresponding mathematical function, in the
following cases:
20 * by any forward or inverse trigonometric function with specified cycle,
when the value of the parameter Cycle is zero or negative;
21 * by the Log function with specified base, when the value of the
parameter Base is zero, one, or negative;
22 * by the Sqrt and Log functions, when the value of the parameter X is
negative;
23 * by the exponentiation operator, when the value of the left operand is
negative or when both operands have the value zero;
24 * by the Arcsin, Arccos, and Arctanh functions, when the absolute value
of the parameter X exceeds one;
25 * by the Arctan and Arccot functions, when the parameters X and Y both
have the value zero;
26 * by the Arccosh function, when the value of the parameter X is less
than one; and
27 * by the Arccoth function, when the absolute value of the parameter X is
less than one.
28 {Division_Check [partial]} {check, language-defined (Division_Check)}
{Constraint_Error (raised by failure of run-time check)} The exception
Constraint_Error is raised, signaling a pole of the mathematical function
(analogous to dividing by zero), in the following cases, provided that
Float_Type'Machine_Overflows is True:
29 * by the Log, Cot, and Coth functions, when the value of the parameter X
is zero;
30 * by the exponentiation operator, when the value of the left operand is
zero and the value of the exponent is negative;
31 * by the Tan function with specified cycle, when the value of the
parameter X is an odd multiple of the quarter cycle;
32 * by the Cot function with specified cycle, when the value of the
parameter X is zero or a multiple of the half cycle; and
33 * by the Arctanh and Arccoth functions, when the absolute value of the
parameter X is one.
34 {Constraint_Error (raised by failure of run-time check)} [Constraint_Error
can also be raised when a finite result overflows (see G.2.4); this may occur
for parameter values sufficiently near poles, and, in the case of some of the
functions, for parameter values with sufficiently large
magnitudes.]{unspecified [partial]} When Float_Type'Machine_Overflows is False, the result
at poles is unspecified.
34.a Reason: The purpose of raising Constraint_Error (rather than
Numerics.Argument_Error) at the poles of a function, when
Float_Type'Machine_Overflows is True, is to provide continuous
behavior as the actual parameters of the function approach the
pole and finally reach it.
34.b Discussion: It is anticipated that an Ada binding to IEC 559:1989
will be developed in the future. As part of such a binding, the
Machine_Overflows attribute of a conformant floating point type
will be specified to yield False, which will permit both the
predefined arithmetic operations and implementations of the
elementary functions to deliver signed infinities (and set the
overflow flag defined by the binding) instead of raising
Constraint_Error in overflow situations, when traps are disabled.
Similarly, it is appropriate for the elementary functions to
deliver signed infinities (and set the zero-divide flag defined by
the binding) instead of raising Constraint_Error at poles, when
traps are disabled. Finally, such a binding should also specify
the behavior of the elementary functions, when sensible, given
parameters with infinite values.
35 When one parameter of a function with multiple parameters represents a
pole and another is outside the function's domain, the latter takes precedence
(i.e., Numerics.Argument_Error is raised).
Implementation Requirements
36 In the implementation of Numerics.Generic_Elementary_Functions, the range
of intermediate values allowed during the calculation of a final result shall
not be affected by any range constraint of the subtype Float_Type.
36.a Implementation Note: Implementations of
Numerics.Generic_Elementary_Functions written in Ada should
therefore avoid declaring local variables of subtype Float_Type;
the subtype Float_Type'Base should be used instead.
37 {prescribed result (for the evaluation of an elementary function)} In the
following cases, evaluation of an elementary function shall yield the
prescribed result, provided that the preceding rules do not call for an
exception to be raised:
38 * When the parameter X has the value zero, the Sqrt, Sin, Arcsin, Tan,
Sinh, Arcsinh, Tanh, and Arctanh functions yield a result of zero, and
the Exp, Cos, and Cosh functions yield a result of one.
39 * When the parameter X has the value one, the Sqrt function yields a
result of one, and the Log, Arccos, and Arccosh functions yield a
result of zero.
40 * When the parameter Y has the value zero and the parameter X has a
positive value, the Arctan and Arccot functions yield a result of zero.
41 * The results of the Sin, Cos, Tan, and Cot functions with specified
cycle are exact when the mathematical result is zero; those of the
first two are also exact when the mathematical result is ± 1.0.
42 * Exponentiation by a zero exponent yields the value one. Exponentiation
by a unit exponent yields the value of the left operand.
Exponentiation of the value one yields the value one. Exponentiation
of the value zero yields the value zero.
43 Other accuracy requirements for the elementary functions, which apply only
in implementations conforming to the Numerics Annex, and then only in the "
strict" mode defined there (see G.2), are given in G.2.4.
44 When Float_Type'Signed_Zeros is True, the sign of a zero result shall be
as follows:
45 * A prescribed zero result delivered at the origin by one of the odd
functions (Sin, Arcsin, Sinh, Arcsinh, Tan, Arctan or Arccot as a
function of Y when X is fixed and positive, Tanh, and Arctanh) has the
sign of the parameter X (Y, in the case of Arctan or Arccot).
46 * A prescribed zero result delivered by one of the odd functions away
from the origin, or by some other elementary function, has an
implementation-defined sign.
46.a Implementation defined: The sign of a zero result from some of the
operators or functions in Numerics.Generic_Elementary_Functions,
when Float_Type'Signed_Zeros is True.
47 * [A zero result that is not a prescribed result (i.e., one that results
from rounding or underflow) has the correct mathematical sign.]
47.a Reason: This is a consequence of the rules specified in IEC
559:1989 as they apply to underflow situations with traps
disabled.
Implementation Permissions
48 The nongeneric equivalent packages may, but need not, be actual
instantiations of the generic package for the appropriate predefined type.
Wording Changes from Ada 83
48.a The semantics of Numerics.Generic_Elementary_Functions differs
from Generic_Elementary_Functions as defined in ISO/IEC DIS 11430
(for Ada 83) in the following ways:
48.b * The generic package is a child unit of the package defining
the Argument_Error exception.
48.c * DIS 11430 specified names for the nongeneric equivalents, if
provided. Here, those nongeneric equivalents are required.
48.d * Implementations are not allowed to impose an optional
restriction that the generic actual parameter associated with
Float_Type be unconstrained. (In view of the ability to
declare variables of subtype Float_Type'Base in
implementations of Numerics.Generic_Elementary_Functions, this
flexibility is no longer needed.)
48.e * The sign of a prescribed zero result at the origin of the odd
functions is specified, when Float_Type'Signed_Zeros is True.
This conforms with recommendations of Kahan and other
numerical analysts.
48.f * The dependence of Arctan and Arccot on the sign of a parameter
value of zero is tied to the value of Float_Type'Signed_Zeros.
48.g * Sqrt is prescribed to yield a result of one when its parameter
has the value one. This guarantee makes it easier to achieve
certain prescribed results of the complex elementary functions
(see G.1.2, "Complex Elementary Functions").
48.h * Conformance to accuracy requirements is conditional.
Wording Changes from Ada 95
48.i/2 {8652/0020} {AI95-00126-01} Corrigendum: Explicitly stated that
the nongeneric equivalents of Generic_Elementary_Functions are
pure.
A.5.2 Random Number Generation
1 [Facilities for the generation of pseudo-random floating point numbers are
provided in the package Numerics.Float_Random; the generic package
Numerics.Discrete_Random provides similar facilities for the generation of
pseudo-random integers and pseudo-random values of enumeration types.
{random number} For brevity, pseudo-random values of any of these types are
called random numbers.
2 Some of the facilities provided are basic to all applications of random
numbers. These include a limited private type each of whose objects serves as
the generator of a (possibly distinct) sequence of random numbers; a function
to obtain the "next" random number from a given sequence of random numbers
(that is, from its generator); and subprograms to initialize or reinitialize a
given generator to a time-dependent state or a state denoted by a single
integer.
3 Other facilities are provided specifically for advanced applications.
These include subprograms to save and restore the state of a given generator;
a private type whose objects can be used to hold the saved state of a
generator; and subprograms to obtain a string representation of a given
generator state, or, given such a string representation, the corresponding
state.]
3.a Discussion: These facilities support a variety of requirements
ranging from repeatable sequences (for debugging) to unique
sequences in each execution of a program.
Static Semantics
4 The library package Numerics.Float_Random has the following declaration:
5 package Ada.Numerics.Float_Random is
6 -- Basic facilities
7 type Generator is limited private;
8 subtype Uniformly_Distributed is Float range 0.0 .. 1.0;
function Random (Gen : Generator) return Uniformly_Distributed;
9 procedure Reset (Gen : in Generator;
Initiator : in Integer);
procedure Reset (Gen : in Generator);
10 -- Advanced facilities
11 type State is private;
12 procedure Save (Gen : in Generator;
To_State : out State);
procedure Reset (Gen : in Generator;
From_State : in State);
13 Max_Image_Width : constant := implementation-defined integer value;
14 function Image (Of_State : State) return String;
function Value (Coded_State : String) return State;
15 private
... -- not specified by the language
end Ada.Numerics.Float_Random;
15.1/2 {AI95-00360-01} The type Generator needs finalization (see 7.6).
16 The generic library package Numerics.Discrete_Random has the following
declaration:
17
generic
type Result_Subtype is (<>);
package Ada.Numerics.Discrete_Random is
18 -- Basic facilities
19 type Generator is limited private;
20 function Random (Gen : Generator) return Result_Subtype;
21 procedure Reset (Gen : in Generator;
Initiator : in Integer);
procedure Reset (Gen : in Generator);
22 -- Advanced facilities
23 type State is private;
24 procedure Save (Gen : in Generator;
To_State : out State);
procedure Reset (Gen : in Generator;
From_State : in State);
25 Max_Image_Width : constant := implementation-defined integer value;
26 function Image (Of_State : State) return String;
function Value (Coded_State : String) return State;
27 private
... -- not specified by the language
end Ada.Numerics.Discrete_Random;
27.a Implementation defined: The value of
Numerics.Float_Random.Max_Image_Width.
27.b Implementation defined: The value of
Numerics.Discrete_Random.Max_Image_Width.
27.c/1 Implementation Note: {8652/0097} {AI95-00115-01} The following is
a possible implementation of the private part of
Numerics.Float_Random (assuming the presence of "with
Ada.Finalization;" as a context clause):
27.d type State is ...;
type Access_State is access State;
type Generator is new Finalization.Limited_Controlled with
record
S : Access_State := new State'(...);
end record;
procedure Finalize (G : in out Generator);
27.d.1/2 {8652/0097} {AI95-00115-01} {AI95-00344-01}
Numerics.Discrete_Random.Generator also can be implemented this
way.
27.e Clearly some level of indirection is required in the
implementation of a Generator, since the parameter mode is in for
all operations on a Generator. For this reason,
Numerics.Float_Random and Numerics.Discrete_Random cannot be
declared pure.
27.1/2 {AI95-00360-01} The type Generator needs finalization (see 7.6) in
every instantiation of Numerics.Discrete_Random.
28 An object of the limited private type Generator is associated with a
sequence of random numbers. Each generator has a hidden (internal) state,
which the operations on generators use to determine the position in the
associated sequence. {unspecified [partial]} All generators are implicitly
initialized to an unspecified state that does not vary from one program
execution to another; they may also be explicitly initialized, or
reinitialized, to a time-dependent state, to a previously saved state, or to a
state uniquely denoted by an integer value.
28.a Discussion: The repeatability provided by the implicit
initialization may be exploited for testing or debugging purposes.
29 An object of the private type State can be used to hold the internal state
of a generator. Such objects are only needed if the application is designed to
save and restore generator states or to examine or manufacture them.
30 The operations on generators affect the state and therefore the future
values of the associated sequence. The semantics of the operations on
generators and states are defined below.
31 function Random (Gen : Generator) return Uniformly_Distributed;
function Random (Gen : Generator) return Result_Subtype;
32 Obtains the "next" random number from the given generator,
relative to its current state, according to an
implementation-defined algorithm. The result of the function in
Numerics.Float_Random is delivered as a value of the subtype
Uniformly_Distributed, which is a subtype of the predefined type
Float having a range of 0.0 .. 1.0. The result of the function in
an instantiation of Numerics.Discrete_Random is delivered as a
value of the generic formal subtype Result_Subtype.
32.a/2 This paragraph was deleted.
32.a.1/2 Discussion: The algorithm is the subject of a
Documentation Requirement, so we don't separately summarize this
implementation-defined item.
32.b Reason: The requirement for a level of indirection in accessing
the internal state of a generator arises from the desire to make
Random a function, rather than a procedure.
33 procedure Reset (Gen : in Generator;
Initiator : in Integer);
procedure Reset (Gen : in Generator);
34 {unspecified [partial]} Sets the state of the specified generator
to one that is an unspecified function of the value of the
parameter Initiator (or to a time-dependent state, if only a
generator parameter is specified).
{Time-dependent Reset procedure (of the random number generator)}
The latter form of the procedure is known as the time-dependent
Reset procedure.
34.a Implementation Note: The time-dependent Reset procedure can be
implemented by mapping the current time and date as determined by
the system clock into a state, but other implementations are
possible. For example, a white-noise generator or a radioactive
source can be used to generate time-dependent states.
35 procedure Save (Gen : in Generator;
To_State : out State);
procedure Reset (Gen : in Generator;
From_State : in State);
36 Save obtains the current state of a generator. Reset gives a
generator the specified state. A generator that is reset to a
state previously obtained by invoking Save is restored to the
state it had when Save was invoked.
37 function Image (Of_State : State) return String;
function Value (Coded_State : String) return State;
38 Image provides a representation of a state coded (in an
implementation-defined way) as a string whose length is bounded by
the value of Max_Image_Width. Value is the inverse of Image:
Value(Image(S)) = S for each state S that can be obtained from a
generator by invoking Save.
38.a Implementation defined: The string representation of a random
number generator's state.
Dynamic Semantics
39 {Range_Check [partial]} {check, language-defined (Range_Check)}
{Constraint_Error (raised by failure of run-time check)} Instantiation of
Numerics.Discrete_Random with a subtype having a null range raises
Constraint_Error.
40/1 This paragraph was deleted.{8652/0050} {AI95-00089}
Bounded (Run-Time) Errors
40.1/1 {8652/0050} {AI95-00089} It is a bounded error to invoke Value with a
string that is not the image of any generator state.
{Program_Error (raised by failure of run-time check)}
{Constraint_Error (raised by failure of run-time check)} If the error is
detected, Constraint_Error or Program_Error is raised. Otherwise, a call to
Reset with the resulting state will produce a generator such that calls to
Random with this generator will produce a sequence of values of the
appropriate subtype, but which might not be random in character. That is, the
sequence of values might not fulfill the implementation requirements of this
subclause.
Implementation Requirements
41 A sufficiently long sequence of random numbers obtained by successive
calls to Random is approximately uniformly distributed over the range of the
result subtype.
42 The Random function in an instantiation of Numerics.Discrete_Random is
guaranteed to yield each value in its result subtype in a finite number of
calls, provided that the number of such values does not exceed 2 (15).
43 Other performance requirements for the random number generator, which
apply only in implementations conforming to the Numerics Annex, and then only
in the "strict" mode defined there (see G.2), are given in G.2.5.
Documentation Requirements
44 No one algorithm for random number generation is best for all
applications. To enable the user to determine the suitability of the random
number generators for the intended application, the implementation shall
describe the algorithm used and shall give its period, if known exactly, or a
lower bound on the period, if the exact period is unknown. Periods that are so
long that the periodicity is unobservable in practice can be described in such
terms, without giving a numerical bound.
44.a/2 Documentation Requirement: The algorithm used for random number
generation, including a description of its period.
45 The implementation also shall document the minimum time interval between
calls to the time-dependent Reset procedure that are guaranteed to initiate
different sequences, and it shall document the nature of the strings that
Value will accept without raising Constraint_Error.
45.a/2 This paragraph was deleted.
45.b/2 Documentation Requirement: The minimum time interval between calls
to the time-dependent Reset procedure that is guaranteed to
initiate different random number sequences.
Implementation Advice
46 Any storage associated with an object of type Generator should be
reclaimed on exit from the scope of the object.
46.a.1/2 Implementation Advice: Any storage associated with an object of
type Generator of the random number packages should be reclaimed
on exit from the scope of the object.
46.a Ramification: A level of indirection is implicit in the semantics
of the operations, given that they all take parameters of mode in.
This implies that the full type of Generator probably should be a
controlled type, with appropriate finalization to reclaim any
heap-allocated storage.
47 If the generator period is sufficiently long in relation to the number of
distinct initiator values, then each possible value of Initiator passed to
Reset should initiate a sequence of random numbers that does not, in a
practical sense, overlap the sequence initiated by any other value. If this is
not possible, then the mapping between initiator values and generator states
should be a rapidly varying function of the initiator value.
47.a/2 Implementation Advice: Each value of Initiator passed to Reset for
the random number packages should initiate a distinct sequence of
random numbers, or, if that is not possible, be at least a rapidly
varying function of the initiator value.
NOTES
48 14 If two or more tasks are to share the same generator, then the
tasks have to synchronize their access to the generator as for any
shared variable (see 9.10).
49 15 Within a given implementation, a repeatable random number sequence
can be obtained by relying on the implicit initialization of
generators or by explicitly initializing a generator with a repeatable
initiator value. Different sequences of random numbers can be obtained
from a given generator in different program executions by explicitly
initializing the generator to a time-dependent state.
50 16 A given implementation of the Random function in
Numerics.Float_Random may or may not be capable of delivering the
values 0.0 or 1.0. Portable applications should assume that these
values, or values sufficiently close to them to behave
indistinguishably from them, can occur. If a sequence of random
integers from some fixed range is needed, the application should use
the Random function in an appropriate instantiation of
Numerics.Discrete_Random, rather than transforming the result of the
Random function in Numerics.Float_Random. However, some applications
with unusual requirements, such as for a sequence of random integers
each drawn from a different range, will find it more convenient to
transform the result of the floating point Random function. For M >=
1, the expression
51 Integer(Float(M) * Random(G)) mod M
52 transforms the result of Random(G) to an integer uniformly distributed
over the range 0 .. M-1; it is valid even if Random delivers 0.0 or
1.0. Each value of the result range is possible, provided that M is
not too large. Exponentially distributed (floating point) random
numbers with mean and standard deviation 1.0 can be obtained by the
transformation
53/2 {AI95-00434-01} -Log(Random(G) + Float'Model_Small)
54 where Log comes from Numerics.Elementary_Functions (see A.5.1); in
this expression, the addition of Float'Model_Small avoids the
exception that would be raised were Log to be given the value zero,
without affecting the result (in most implementations) when Random
returns a nonzero value.
Examples
55 Example of a program that plays a simulated dice game:
56 with Ada.Numerics.Discrete_Random;
procedure Dice_Game is
subtype Die is Integer range 1 .. 6;
subtype Dice is Integer range 2*Die'First .. 2*Die'Last;
package Random_Die is new Ada.Numerics.Discrete_Random (Die);
use Random_Die;
G : Generator;
D : Dice;
begin
Reset (G); -- Start the generator in a unique state in each run
loop
-- Roll a pair of dice; sum and process the results
D := Random(G) + Random(G);
...
end loop;
end Dice_Game;
57 Example of a program that simulates coin tosses:
58 with Ada.Numerics.Discrete_Random;
procedure Flip_A_Coin is
type Coin is (Heads, Tails);
package Random_Coin is new Ada.Numerics.Discrete_Random (Coin);
use Random_Coin;
G : Generator;
begin
Reset (G); -- Start the generator in a unique state in each run
loop
-- Toss a coin and process the result
case Random(G) is
when Heads =>
...
when Tails =>
...
end case;
...
end loop;
end Flip_A_Coin;
59 Example of a parallel simulation of a physical system, with a separate
generator of event probabilities in each task:
60 with Ada.Numerics.Float_Random;
procedure Parallel_Simulation is
use Ada.Numerics.Float_Random;
task type Worker is
entry Initialize_Generator (Initiator : in Integer);
...
end Worker;
W : array (1 .. 10) of Worker;
task body Worker is
G : Generator;
Probability_Of_Event : Uniformly_Distributed;
begin
accept Initialize_Generator (Initiator : in Integer) do
Reset (G, Initiator);
end Initialize_Generator;
loop
...
Probability_Of_Event := Random(G);
...
end loop;
end Worker;
begin
-- Initialize the generators in the Worker tasks to different states
for I in W'Range loop
W(I).Initialize_Generator (I);
end loop;
... -- Wait for the Worker tasks to terminate
end Parallel_Simulation;
NOTES
61 17 Notes on the last example: Although each Worker task initializes
its generator to a different state, those states will be the same in
every execution of the program. The generator states can be
initialized uniquely in each program execution by instantiating
Ada.Numerics.Discrete_Random for the type Integer in the main
procedure, resetting the generator obtained from that instance to a
time-dependent state, and then using random integers obtained from
that generator to initialize the generators in each Worker task.
Incompatibilities With Ada 95
61.a/2 {AI95-00360-01} {incompatibilities with Ada 95} Amendment
Correction: Type Generator in Numerics.Float_Random and in an
instance of Numerics.Discrete_Random is defined to need
finalization. If the restriction No_Nested_Finalization (see D.7)
applies to the partition, and Generator does not have a controlled
part, it will not be allowed in local objects in Ada 2005 whereas
it would be allowed in original Ada 95. Such code is not portable,
as another Ada compiler may have a controlled part in Generator,
and thus would be illegal.
Wording Changes from Ada 95
61.b/2 {8652/0050} {AI95-00089-01} Corrigendum: Made the passing of an
incorrect Image of a generator a bounded error, as it may not be
practical to check for problems (if a generator consists of
several related values).
A.5.3 Attributes of Floating Point Types
Static Semantics
1 {representation-oriented attributes (of a floating point subtype)} The
following representation-oriented attributes are defined for every subtype S
of a floating point type T.
2 S'Machine_Radix
Yields the radix of the hardware representation of the type T.
The value of this attribute is of the type universal_integer.
3 {canonical form} The values of other representation-oriented attributes of
a floating point subtype, and of the "primitive function" attributes of a
floating point subtype described later, are defined in terms of a particular
representation of nonzero values called the canonical form. The canonical form
(for the type T) is the form
± mantissa · T'Machine_Radix(exponent)
where
4 * mantissa is a fraction in the number base T'Machine_Radix, the first
digit of which is nonzero, and
5 * exponent is an integer.
6 S'Machine_Mantissa
Yields the largest value of p such that every value
expressible in the canonical form (for the type T), having a
p-digit mantissa and an exponent between T'Machine_Emin and
T'Machine_Emax, is a machine number (see 3.5.7) of the type T.
This attribute yields a value of the type universal_integer.
6.a Ramification: Values of a type held in an extended register are,
in general, not machine numbers of the type, since they cannot be
expressed in the canonical form with a sufficiently short
mantissa.
7 S'Machine_Emin
Yields the smallest (most negative) value of exponent such
that every value expressible in the canonical form (for the
type T), having a mantissa of T'Machine_Mantissa digits, is a
machine number (see 3.5.7) of the type T. This attribute
yields a value of the type universal_integer.
8 S'Machine_Emax
Yields the largest (most positive) value of exponent such that
every value expressible in the canonical form (for the type
T), having a mantissa of T'Machine_Mantissa digits, is a
machine number (see 3.5.7) of the type T. This attribute
yields a value of the type universal_integer.
8.a Ramification: Note that the above definitions do not determine
unique values for the representation-oriented attributes of
floating point types. The implementation may choose any set of
values that collectively satisfies the definitions.
9 S'Denorm Yields the value True if every value expressible in the form
± mantissa · T'Machine_Radix(T'Machine_Emin)
where mantissa is a nonzero T'Machine_Mantissa-digit fraction
in the number base T'Machine_Radix, the first digit of which
is zero, is a machine number (see 3.5.7) of the type T; yields
the value False otherwise. The value of this attribute is of
the predefined type Boolean.
10 {denormalized number} The values described by the formula in the
definition of S'Denorm are called denormalized numbers. {normalized number} A
nonzero machine number that is not a denormalized number is a normalized
number. {represented in canonical form} {canonical-form representation} A
normalized number x of a given type T is said to be represented in canonical
form when it is expressed in the canonical form (for the type T) with a
mantissa having T'Machine_Mantissa digits; the resulting form is the
canonical-form representation of x.
10.a Discussion: The intent is that S'Denorm be True when such
denormalized numbers exist and are generated in the circumstances
defined by IEC 559:1989, though the latter requirement is not
formalized here.
11 S'Machine_Rounds
Yields the value True if rounding is performed on inexact
results of every predefined operation that yields a result of
the type T; yields the value False otherwise. The value of
this attribute is of the predefined type Boolean.
11.a Discussion: It is difficult to be more precise about what it means
to round the result of a predefined operation. If the
implementation does not use extended registers, so that every
arithmetic result is necessarily a machine number, then rounding
seems to imply two things:
11.b * S'Model_Mantissa = S'Machine_Mantissa, so that operand
preperturbation never occurs;
11.c * when the exact mathematical result is not a machine number,
the result of a predefined operation must be the nearer of the
two adjacent machine numbers.
11.d Technically, this attribute should yield False when extended
registers are used, since a few computed results will cross over
the half-way point as a result of double rounding, if and when a
value held in an extended register has to be reduced in precision
to that of the machine numbers. It does not seem desirable to
preclude the use of extended registers when S'Machine_Rounds could
otherwise be True.
12 S'Machine_Overflows
Yields the value True if overflow and divide-by-zero are
detected and reported by raising Constraint_Error for every
predefined operation that yields a result of the type T;
yields the value False otherwise. The value of this attribute
is of the predefined type Boolean.
13 S'Signed_Zeros
Yields the value True if the hardware representation for the
type T has the capability of representing both positively and
negatively signed zeros, these being generated and used by the
predefined operations of the type T as specified in IEC
559:1989; yields the value False otherwise. The value of this
attribute is of the predefined type Boolean.
14 {normalized exponent} For every value x of a floating point type T, the
normalized exponent of x is defined as follows:
15 * the normalized exponent of zero is (by convention) zero;
16 * for nonzero x, the normalized exponent of x is the unique integer k
such that T'Machine_Radix(k-1) <= |x| < T'Machine_Radix(k).
16.a Ramification: The normalized exponent of a normalized number x is
the value of exponent in the canonical-form representation of x.
16.b The normalized exponent of a denormalized number is less than the
value of T'Machine_Emin.
17 {primitive function} The following primitive function attributes are
defined for any subtype S of a floating point type T.
18 S'Exponent S'Exponent denotes a function with the following
specification:
19 function S'Exponent (X : T)
return universal_integer
20 The function yields the normalized exponent of X.
21 S'Fraction S'Fraction denotes a function with the following
specification:
22 function S'Fraction (X : T)
return T
23 The function yields the value X · T'Machine_Radix(-k), where k
is the normalized exponent of X. A zero result[, which can
only occur when X is zero,] has the sign of X.
23.a Discussion: Informally, when X is a normalized number, the result
is the value obtained by replacing the exponent by zero in the
canonical-form representation of X.
23.b Ramification: Except when X is zero, the magnitude of the result
is greater than or equal to the reciprocal of T'Machine_Radix and
less than one; consequently, the result is always a normalized
number, even when X is a denormalized number.
23.c Implementation Note: When X is a denormalized number, the result
is the value obtained by replacing the exponent by zero in the
canonical-form representation of the result of scaling X up
sufficiently to normalize it.
24 S'Compose S'Compose denotes a function with the following specification:
25 function S'Compose (Fraction : T;
Exponent : universal_integer)
return T
26 {Constraint_Error (raised by failure of run-time check)} Let v
be the value Fraction · T'Machine_Radix(Exponent-k), where k
is the normalized exponent of Fraction. If v is a machine
number of the type T, or if |v| >= T'Model_Small, the function
yields v; otherwise, it yields either one of the machine
numbers of the type T adjacent to v. {Range_Check [partial]}
{check, language-defined (Range_Check)} Constraint_Error is
optionally raised if v is outside the base range of S. A zero
result has the sign of Fraction when S'Signed_Zeros is True.
26.a Discussion: Informally, when Fraction and v are both normalized
numbers, the result is the value obtained by replacing the
exponent by Exponent in the canonical-form representation of
Fraction.
26.b Ramification: If Exponent is less than T'Machine_Emin and Fraction
is nonzero, the result is either zero, T'Model_Small, or (if
T'Denorm is True) a denormalized number.
27 S'Scaling S'Scaling denotes a function with the following specification:
28 function S'Scaling (X : T;
Adjustment : universal_integer)
return T
29 {Constraint_Error (raised by failure of run-time check)} Let v
be the value X · T'Machine_Radix(Adjustment). If v is a
machine number of the type T, or if |v| >= T'Model_Small, the
function yields v; otherwise, it yields either one of the
machine numbers of the type T adjacent to v. {Range_Check
[partial]} {check, language-defined (Range_Check)}
Constraint_Error is optionally raised if v is outside the base
range of S. A zero result has the sign of X when
S'Signed_Zeros is True.
29.a Discussion: Informally, when X and v are both normalized numbers,
the result is the value obtained by increasing the exponent by
Adjustment in the canonical-form representation of X.
29.b Ramification: If Adjustment is sufficiently small (i.e.,
sufficiently negative), the result is either zero, T'Model_Small,
or (if T'Denorm is True) a denormalized number.
30 S'Floor S'Floor denotes a function with the following specification:
31 function S'Floor (X : T)
return T
32 The function yields the value Floor(X), i.e., the largest
(most positive) integral value less than or equal to X. When X
is zero, the result has the sign of X; a zero result otherwise
has a positive sign.
33 S'Ceiling S'Ceiling denotes a function with the following specification:
34 function S'Ceiling (X : T)
return T
35 The function yields the value Ceiling(X), i.e., the smallest
(most negative) integral value greater than or equal to X.
When X is zero, the result has the sign of X; a zero result
otherwise has a negative sign when S'Signed_Zeros is True.
36 S'Rounding S'Rounding denotes a function with the following
specification:
37 function S'Rounding (X : T)
return T
38 The function yields the integral value nearest to X, rounding
away from zero if X lies exactly halfway between two integers.
A zero result has the sign of X when S'Signed_Zeros is True.
39 S'Unbiased_Rounding
S'Unbiased_Rounding denotes a function with the following
specification:
40 function S'Unbiased_Rounding (X : T)
return T
41 The function yields the integral value nearest to X, rounding
toward the even integer if X lies exactly halfway between two
integers. A zero result has the sign of X when S'Signed_Zeros
is True.
41.1/2 S'Machine_Rounding
{AI95-00267-01} S'Machine_Rounding denotes a function with the
following specification:
41.2/2 function S'Machine_Rounding (X : T)
return T
41.3/2 The function yields the integral value nearest to X. If X lies
exactly halfway between two integers, one of those integers is
returned, but which of them is returned is unspecified. A zero
result has the sign of X when S'Signed_Zeros is True. This
function provides access to the rounding behavior which is
most efficient on the target processor.{unspecified
[partial]}
41.a.1/2 Discussion: We leave the rounding unspecified, so that users
cannot depend on a particular rounding. This attribute is intended
for use in cases where the particular rounding chosen is
irrelevant. If there is a need to know which way values halfway
between two integers are rounded, one of the other rounding
attributes should be used.
42 S'Truncation
S'Truncation denotes a function with the following
specification:
43 function S'Truncation (X : T)
return T
44 The function yields the value Ceiling(X) when X is negative,
and Floor(X) otherwise. A zero result has the sign of X when
S'Signed_Zeros is True.
45 S'Remainder S'Remainder denotes a function with the following
specification:
46 function S'Remainder (X, Y : T)
return T
47 {Constraint_Error (raised by failure of run-time check)} For
nonzero Y, let v be the value X - n · Y, where n is the
integer nearest to the exact value of X/Y; if |n - X/Y| = 1/2,
then n is chosen to be even. If v is a machine number of the
type T, the function yields v; otherwise, it yields zero.
{Division_Check [partial]}
{check, language-defined (Division_Check)} Constraint_Error is
raised if Y is zero. A zero result has the sign of X when
S'Signed_Zeros is True.
47.a Ramification: The magnitude of the result is less than or equal to
one-half the magnitude of Y.
47.b Discussion: Given machine numbers X and Y of the type T, v is
necessarily a machine number of the type T, except when Y is in
the neighborhood of zero, X is sufficiently close to a multiple of
Y, and T'Denorm is False.
48 S'Adjacent S'Adjacent denotes a function with the following
specification:
49 function S'Adjacent (X, Towards : T)
return T
50 {Constraint_Error (raised by failure of run-time check)} If
Towards = X, the function yields X; otherwise, it yields the
machine number of the type T adjacent to X in the direction of
Towards, if that machine number exists. {Range_Check
[partial]} {check, language-defined (Range_Check)} If the
result would be outside the base range of S, Constraint_Error
is raised. When T'Signed_Zeros is True, a zero result has the
sign of X. When Towards is zero, its sign has no bearing on
the result.
50.a Ramification: The value of S'Adjacent(0.0, 1.0) is the smallest
normalized positive number of the type T when T'Denorm is False
and the smallest denormalized positive number of the type T when
T'Denorm is True.
51 S'Copy_Sign S'Copy_Sign denotes a function with the following
specification:
52 function S'Copy_Sign (Value, Sign : T)
return T
53 {Constraint_Error (raised by failure of run-time check)} If
the value of Value is nonzero, the function yields a result
whose magnitude is that of Value and whose sign is that of
Sign; otherwise, it yields the value zero. {Range_Check
[partial]} {check, language-defined (Range_Check)}
Constraint_Error is optionally raised if the result is outside
the base range of S. A zero result has the sign of Sign when
S'Signed_Zeros is True.
53.a Discussion: S'Copy_Sign is provided for convenience in restoring
the sign to a quantity from which it has been temporarily removed,
or to a related quantity. When S'Signed_Zeros is True, it is also
instrumental in determining the sign of a zero quantity, when
required. (Because negative and positive zeros compare equal in
systems conforming to IEC 559:1989, a negative zero does not
appear to be negative when compared to zero.) The sign
determination is accomplished by transferring the sign of the zero
quantity to a nonzero quantity and then testing for a negative
result.
54 S'Leading_Part
S'Leading_Part denotes a function with the following
specification:
55 function S'Leading_Part (X : T;
Radix_Digits : universal_integer)
return T
56 Let v be the value T'Machine_Radix(k-Radix_Digits), where k is
the normalized exponent of X. The function yields the value
57 * Floor(X/v) · v, when X is nonnegative and Radix_Digits is
positive;
58 * Ceiling(X/v) · v, when X is negative and Radix_Digits is
positive.
59 {Constraint_Error (raised by failure of run-time check)}
{Range_Check [partial]}
{check, language-defined (Range_Check)} Constraint_Error is
raised when Radix_Digits is zero or negative. A zero result[,
which can only occur when X is zero,] has the sign of X.
59.a Discussion: Informally, if X is nonzero, the result is the value
obtained by retaining only the specified number of (leading)
significant digits of X (in the machine radix), setting all other
digits to zero.
59.b Implementation Note: The result can be obtained by first scaling X
up, if necessary to normalize it, then masking the mantissa so as
to retain only the specified number of leading digits, then
scaling the result back down if X was scaled up.
60 S'Machine S'Machine denotes a function with the following specification:
61 function S'Machine (X : T)
return T
62 {Constraint_Error (raised by failure of run-time check)} If X
is a machine number of the type T, the function yields X;
otherwise, it yields the value obtained by rounding or
truncating X to either one of the adjacent machine numbers of
the type T. {Range_Check [partial]}
{check, language-defined (Range_Check)} Constraint_Error is
raised if rounding or truncating X to the precision of the
machine numbers results in a value outside the base range of
S. A zero result has the sign of X when S'Signed_Zeros is
True.
62.a Discussion: All of the primitive function attributes except
Rounding and Machine correspond to subprograms in the
Generic_Primitive_Functions generic package proposed as a separate
ISO standard (ISO/IEC DIS 11729) for Ada 83. The Scaling,
Unbiased_Rounding, and Truncation attributes correspond to the
Scale, Round, and Truncate functions, respectively, in
Generic_Primitive_Functions. The Rounding attribute rounds away
from zero; this functionality was not provided in
Generic_Primitive_Functions. The name Round was not available for
either of the primitive function attributes that perform rounding,
since an attribute of that name is used for a different purpose
for decimal fixed point types. Likewise, the name Scale was not
available, since an attribute of that name is also used for a
different purpose for decimal fixed point types. The functionality
of the Machine attribute was also not provided in
Generic_Primitive_Functions. The functionality of the Decompose
procedure of Generic_Primitive_Functions is only provided in the
form of the separate attributes Exponent and Fraction. The
functionality of the Successor and Predecessor functions of
Generic_Primitive_Functions is provided by the extension of the
existing Succ and Pred attributes.
62.b Implementation Note: The primitive function attributes may be
implemented either with appropriate floating point arithmetic
operations or with integer and logical operations that act on
parts of the representation directly. The latter is strongly
encouraged when it is more efficient than the former; it is
mandatory when the former cannot deliver the required accuracy due
to limitations of the implementation's arithmetic operations.
63 {model-oriented attributes (of a floating point subtype)} The following
model-oriented attributes are defined for any subtype S of a floating point
type T.
64 S'Model_Mantissa
If the Numerics Annex is not supported, this attribute yields
an implementation defined value that is greater than or equal
to Ceiling(d · log(10) / log(T'Machine_Radix)) + 1, where d is
the requested decimal precision of T, and less than or equal
to the value of T'Machine_Mantissa. See G.2.2 for further
requirements that apply to implementations supporting the
Numerics Annex. The value of this attribute is of the type
universal_integer.
65 S'Model_Emin
If the Numerics Annex is not supported, this attribute yields
an implementation defined value that is greater than or equal
to the value of T'Machine_Emin. See G.2.2 for further
requirements that apply to implementations supporting the
Numerics Annex. The value of this attribute is of the type
universal_integer.
66 S'Model_Epsilon
Yields the value T'Machine_Radix(1 - T'Model_Mantissa). The
value of this attribute is of the type universal_real.
66.a Discussion: In most implementations, this attribute yields the
absolute value of the difference between one and the smallest
machine number of the type T above one which, when added to one,
yields a machine number different from one. Further discussion can
be found in G.2.2.
67 S'Model_Small
Yields the value T'Machine_Radix(T'Model_Emin - 1). The value
of this attribute is of the type universal_real.
67.a Discussion: In most implementations, this attribute yields the
smallest positive normalized number of the type T, i.e. the number
corresponding to the positive underflow threshold. In some
implementations employing a radix-complement representation for
the type T, the positive underflow threshold is closer to zero
than is the negative underflow threshold, with the consequence
that the smallest positive normalized number does not coincide
with the positive underflow threshold (i.e., it exceeds the
latter). Further discussion can be found in G.2.2.
68 S'Model S'Model denotes a function with the following specification:
69 function S'Model (X : T)
return T
70 If the Numerics Annex is not supported, the meaning of this
attribute is implementation defined; see G.2.2 for the
definition that applies to implementations supporting the
Numerics Annex.
71 S'Safe_First
Yields the lower bound of the safe range (see 3.5.7) of the
type T. If the Numerics Annex is not supported, the value of
this attribute is implementation defined; see G.2.2 for the
definition that applies to implementations supporting the
Numerics Annex. The value of this attribute is of the type
universal_real.
72 S'Safe_Last Yields the upper bound of the safe range (see 3.5.7) of the
type T. If the Numerics Annex is not supported, the value of
this attribute is implementation defined; see G.2.2 for the
definition that applies to implementations supporting the
Numerics Annex. The value of this attribute is of the type
universal_real.
72.a Discussion: A predefined floating point arithmetic operation that
yields a value in the safe range of its result type is guaranteed
not to overflow.
72.b To be honest: An exception is made for exponentiation by a
negative exponent in 4.5.6.
72.c Implementation defined: The values of the Model_Mantissa,
Model_Emin, Model_Epsilon, Model, Safe_First, and Safe_Last
attributes, if the Numerics Annex is not supported.
Incompatibilities With Ada 83
72.d {incompatibilities with Ada 83} The Epsilon and Mantissa
attributes of floating point types are removed from the language
and replaced by Model_Epsilon and Model_Mantissa, which may have
different values (as a result of changes in the definition of
model numbers); the replacement of one set of attributes by
another is intended to convert what would be an inconsistent
change into an incompatible change.
72.e The Emax, Small, Large, Safe_Emax, Safe_Small, and Safe_Large
attributes of floating point types are removed from the language.
Small and Safe_Small are collectively replaced by Model_Small,
which is functionally equivalent to Safe_Small, though it may have
a slightly different value. The others are collectively replaced
by Safe_First and Safe_Last. Safe_Last is functionally equivalent
to Safe_Large, though it may have a different value; Safe_First is
comparable to the negation of Safe_Large but may differ slightly
from it as well as from the negation of Safe_Last. Emax and
Safe_Emax had relatively few uses in Ada 83; T'Safe_Emax can be
computed in the revised language as
Integer'Min(T'Exponent(T'Safe_First), T'Exponent(T'Safe_Last)).
72.f Implementations are encouraged to eliminate the incompatibilities
discussed here by retaining the old attributes, during a
transition period, in the form of implementation-defined
attributes with their former values.
Extensions to Ada 83
72.g {extensions to Ada 83} The Model_Emin attribute is new. It is
conceptually similar to the negation of Safe_Emax attribute of Ada
83, adjusted for the fact that the model numbers now have the
hardware radix. It is a fundamental determinant, along with
Model_Mantissa, of the set of model numbers of a type (see G.2.1).
72.h The Denorm and Signed_Zeros attributes are new, as are all of the
primitive function attributes.
Extensions to Ada 95
72.i/2 {AI95-00388-01} {extensions to Ada 95} The Machine_Rounding
attribute is new.
A.5.4 Attributes of Fixed Point Types
Static Semantics
1 {representation-oriented attributes (of a fixed point subtype)} The
following representation-oriented attributes are defined for every subtype S
of a fixed point type T.
2 S'Machine_Radix
Yields the radix of the hardware representation of the type T.
The value of this attribute is of the type universal_integer.
3 S'Machine_Rounds
Yields the value True if rounding is performed on inexact
results of every predefined operation that yields a result of
the type T; yields the value False otherwise. The value of
this attribute is of the predefined type Boolean.
4 S'Machine_Overflows
Yields the value True if overflow and divide-by-zero are
detected and reported by raising Constraint_Error for every
predefined operation that yields a result of the type T;
yields the value False otherwise. The value of this attribute
is of the predefined type Boolean.
Incompatibilities With Ada 83
4.a {incompatibilities with Ada 83} The Mantissa, Large, Safe_Small,
and Safe_Large attributes of fixed point types are removed from
the language.
4.b Implementations are encouraged to eliminate the resulting
incompatibility by retaining these attributes, during a transition
period, in the form of implementation-defined attributes with
their former values.
Extensions to Ada 83
4.c {extensions to Ada 83} The Machine_Radix attribute is now allowed
for fixed point types. It is also specifiable in an attribute
definition clause (see F.1).
A.6 Input-Output
1/2 {AI95-00285-01} [{input} {output} Input-output is provided through
language-defined packages, each of which is a child of the root package Ada.
The generic packages Sequential_IO and Direct_IO define input-output
operations applicable to files containing elements of a given type. The
generic package Storage_IO supports reading from and writing to an in-memory
buffer. Additional operations for text input-output are supplied in the
packages Text_IO, Wide_Text_IO, and Wide_Wide_Text_IO. Heterogeneous
input-output is provided through the child packages Streams.Stream_IO and
Text_IO.Text_Streams (see also 13.13). The package IO_Exceptions defines the
exceptions needed by the predefined input-output packages.]
Inconsistencies With Ada 83
1.a {inconsistencies with Ada 83} The introduction of Append_File as a
new element of the enumeration type File_Mode in Sequential_IO and
Text_IO, and the introduction of several new declarations in
Text_IO, may result in name clashes in the presence of use
clauses.
Extensions to Ada 83
1.b {extensions to Ada 83} Text_IO enhancements (Get_Immediate,
Look_Ahead, Standard_Error, Modular_IO, Decimal_IO), Wide_Text_IO,
and the stream input-output facilities are new in Ada 95.
Wording Changes from Ada 83
1.c RM83-14.6, "Low Level Input-Output," is removed. This has no
semantic effect, since the package was entirely implementation
defined, nobody actually implemented it, and if they did, they can
always provide it as a vendor-supplied package.
Wording Changes from Ada 95
1.d/2 {AI95-00285-01} Included package Wide_Wide_Text_IO in this
description.
A.7 External Files and File Objects
Static Semantics
1 {external file} {name (of an external file)} {form (of an external file)}
Values input from the external environment of the program, or output to the
external environment, are considered to occupy external files. An external
file can be anything external to the program that can produce a value to be
read or receive a value to be written. An external file is identified by a
string (the name). A second string (the form) gives further system-dependent
characteristics that may be associated with the file, such as the physical
organization or access rights. The conventions governing the interpretation of
such strings shall be documented.
2 {file (as file object)} Input and output operations are expressed as
operations on objects of some file type, rather than directly in terms of the
external files. In the remainder of this section, the term file is always used
to refer to a file object; the term external file is used otherwise.
3 Input-output for sequential files of values of a single element type is
defined by means of the generic package Sequential_IO. In order to define
sequential input-output for a given element type, an instantiation of this
generic unit, with the given type as actual parameter, has to be declared. The
resulting package contains the declaration of a file type (called File_Type)
for files of such elements, as well as the operations applicable to these
files, such as the Open, Read, and Write procedures.
4/2 {AI95-00285-01} Input-output for direct access files is likewise defined
by a generic package called Direct_IO. Input-output in human-readable form is
defined by the (nongeneric) packages Text_IO for Character and String data,
Wide_Text_IO for Wide_Character and Wide_String data, and Wide_Wide_Text_IO
for Wide_Wide_Character and Wide_Wide_String data. Input-output for files
containing streams of elements representing values of possibly different types
is defined by means of the (nongeneric) package Streams.Stream_IO.
5 Before input or output operations can be performed on a file, the file
first has to be associated with an external file. While such an association is
in effect, the file is said to be open, and otherwise the file is said to be
closed.
6 The language does not define what happens to external files after the
completion of the main program and all the library tasks (in particular, if
corresponding files have not been closed).
{access types (input-output unspecified)}
{input-output (unspecified for access types)} {unspecified [partial]} The
effect of input-output for access types is unspecified.
7 {current mode (of an open file)} An open file has a current mode, which is
a value of one of the following enumeration types:
8 type File_Mode is (In_File, Inout_File, Out_File); -- for Direct_IO
9 These values correspond respectively to the cases where only
reading, both reading and writing, or only writing are to be
performed.
10/2 {AI95-00285-01} type File_Mode is (In_File, Out_File, Append_File);
-- for Sequential_IO, Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, and Stream_IO
11 These values correspond respectively to the cases where only
reading, only writing, or only appending are to be performed.
12 The mode of a file can be changed.
13/2 {AI95-00285-01} Several file management operations are common to
Sequential_IO, Direct_IO, Text_IO, Wide_Text_IO, and Wide_Wide_Text_IO. These
operations are described in subclause A.8.2 for sequential and direct files.
Any additional effects concerning text input-output are described in subclause
A.10.2.
14 The exceptions that can be propagated by the execution of an input-output
subprogram are defined in the package IO_Exceptions; the situations in which
they can be propagated are described following the description of the
subprogram (and in clause A.13).
{Storage_Error (raised by failure of run-time check)}
{Program_Error (raised by failure of run-time check)} The exceptions
Storage_Error and Program_Error may be propagated. (Program_Error can only be
propagated due to errors made by the caller of the subprogram.) Finally,
exceptions can be propagated in certain implementation-defined situations.
14.a/2 This paragraph was deleted.
14.b/2 Discussion: The last sentence here is referring to the
documentation requirements in A.13, "Exceptions in Input-Output
", and the documentation summary item is provided there.
NOTES
15/2 18 {AI95-00285-01} Each instantiation of the generic packages
Sequential_IO and Direct_IO declares a different type File_Type. In
the case of Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, and
Streams.Stream_IO, the corresponding type File_Type is unique.
16 19 A bidirectional device can often be modeled as two sequential
files associated with the device, one of mode In_File, and one of mode
Out_File. An implementation may restrict the number of files that may
be associated with a given external file.
Wording Changes from Ada 95
16.a/2 {AI95-00285-01} Included package Wide_Wide_Text_IO in this
description.
A.8 Sequential and Direct Files
Static Semantics
1/2 {AI95-00283-01} {sequential file} {direct file} {stream file} Two kinds of
access to external files are defined in this subclause: sequential access and
direct access. The corresponding file types and the associated operations are
provided by the generic packages Sequential_IO and Direct_IO. A file object to
be used for sequential access is called a sequential file, and one to be used
for direct access is called a direct file. Access to stream files is described
in A.12.1.
2 {sequential access} For sequential access, the file is viewed as a
sequence of values that are transferred in the order of their appearance (as
produced by the program or by the external environment). When the file is
opened with mode In_File or Out_File, transfer starts respectively from or to
the beginning of the file. When the file is opened with mode Append_File,
transfer to the file starts after the last element of the file.
2.a Discussion: Adding stream I/O necessitates a review of the
terminology. In Ada 83, `sequential' implies both the access
method (purely sequential - that is, no indexing or positional
access) and homogeneity. Direct access includes purely sequential
access and indexed access, as well as homogeneity. In Ada 95,
streams allow purely sequential access but also positional access
to an individual element, and are heterogeneous. We considered
generalizing the notion of `sequential file' to include both
Sequential_IO and Stream_IO files, but since streams allow
positional access it seems misleading to call them sequential
files. Or, looked at differently, if the criterion for calling
something a sequential file is whether it permits (versus
requires) purely sequential access, then one could just as soon
regard a Direct_IO file as a sequential file.
2.b It seems better to regard `sequential file' as meaning `only
permitting purely sequential access'; hence we have decided to
supplement `sequential access' and `direct access' with a third
category, informally called `access to streams'. (We decided
against the term `stream access' because of possible confusion
with the Stream_Access type declared in one of the stream
packages.)
3 {direct access} {index (of an element of an open direct file)}
{current size (of an external file)} For direct access, the file is viewed as a
set of elements occupying consecutive positions in linear order; a value can
be transferred to or from an element of the file at any selected position. The
position of an element is specified by its index, which is a number, greater
than zero, of the implementation-defined integer type Count. The first
element, if any, has index one; the index of the last element, if any, is
called the current size; the current size is zero if there are no elements.
The current size is a property of the external file.
4 {current index (of an open direct file)} An open direct file has a current
index, which is the index that will be used by the next read or write
operation. When a direct file is opened, the current index is set to one. The
current index of a direct file is a property of a file object, not of an
external file.
Wording Changes from Ada 95
4.a/2 {AI95-00283-01} Italicized "stream file" to clarify that this is
another kind of file.
A.8.1 The Generic Package Sequential_IO
Static Semantics
1 The generic library package Sequential_IO has the following declaration:
2 with Ada.IO_Exceptions;
generic
type Element_Type(<>) is private;
package Ada.Sequential_IO is
3 type File_Type is limited private;
4 type File_Mode is (In_File, Out_File, Append_File);
5 -- File management
6 procedure Create(File : in out File_Type;
Mode : in File_Mode := Out_File;
Name : in String := "";
Form : in String := "");
7 procedure Open (File : in out File_Type;
Mode : in File_Mode;
Name : in String;
Form : in String := "");
8 procedure Close (File : in out File_Type);
procedure Delete(File : in out File_Type);
procedure Reset (File : in out File_Type; Mode : in File_Mode);
procedure Reset (File : in out File_Type);
9 function Mode (File : in File_Type) return File_Mode;
function Name (File : in File_Type) return String;
function Form (File : in File_Type) return String;
10 function Is_Open(File : in File_Type) return Boolean;
11 -- Input and output operations
12 procedure Read (File : in File_Type; Item : out Element_Type);
procedure Write (File : in File_Type; Item : in Element_Type);
13 function End_Of_File(File : in File_Type) return Boolean;
14 -- Exceptions
15 Status_Error : exception renames IO_Exceptions.Status_Error;
Mode_Error : exception renames IO_Exceptions.Mode_Error;
Name_Error : exception renames IO_Exceptions.Name_Error;
Use_Error : exception renames IO_Exceptions.Use_Error;
Device_Error : exception renames IO_Exceptions.Device_Error;
End_Error : exception renames IO_Exceptions.End_Error;
Data_Error : exception renames IO_Exceptions.Data_Error;
16 private
... -- not specified by the language
end Ada.Sequential_IO;
17/2 {AI95-00360-01} The type File_Type needs finalization (see 7.6) in every
instantiation of Sequential_IO.
Incompatibilities With Ada 83
17.a {incompatibilities with Ada 83} The new enumeration element
Append_File may introduce upward incompatibilities. It is possible
that a program based on the assumption that File_Mode'Last =
Out_File will be illegal (e.g., case statement choice coverage) or
execute with a different effect in Ada 95.
17.a.1/2 This paragraph was deleted.{8652/0097} {AI95-00115-01}
{AI95-00344-01}
Incompatibilities With Ada 95
17.b/2 {AI95-00360-01} {incompatibilities with Ada 95} Amendment
Correction: File_Type in an instance of Sequential_IO is defined
to need finalization. If the restriction No_Nested_Finalization
(see D.7) applies to the partition, and File_Type does not have a
controlled part, it will not be allowed in local objects in Ada
2005 whereas it would be allowed in original Ada 95. Such code is
not portable, as another Ada compiler may have a controlled part
in File_Type, and thus would be illegal.
A.8.2 File Management
Static Semantics
1 The procedures and functions described in this subclause provide for the
control of external files; their declarations are repeated in each of the
packages for sequential, direct, text, and stream input-output. For text
input-output, the procedures Create, Open, and Reset have additional effects
described in subclause A.10.2.
2 procedure Create(File : in out File_Type;
Mode : in File_Mode := default_mode;
Name : in String := "";
Form : in String := "");
3/2 {AI95-00283-01} Establishes a new external file, with the given
name and form, and associates this external file with the given
file. The given file is left open. The current mode of the given
file is set to the given access mode. The default access mode is
the mode Out_File for sequential, stream, and text input-output;
it is the mode Inout_File for direct input-output. For direct
access, the size of the created file is implementation defined.
4 A null string for Name specifies an external file that is not
accessible after the completion of the main program (a temporary
file). A null string for Form specifies the use of the default
options of the implementation for the external file.
5 The exception Status_Error is propagated if the given file is
already open. The exception Name_Error is propagated if the string
given as Name does not allow the identification of an external
file. The exception Use_Error is propagated if, for the specified
mode, the external environment does not support creation of an
external file with the given name (in the absence of Name_Error)
and form.
6 procedure Open(File : in out File_Type;
Mode : in File_Mode;
Name : in String;
Form : in String := "");
7 Associates the given file with an existing external file having
the given name and form, and sets the current mode of the given
file to the given mode. The given file is left open.
8 The exception Status_Error is propagated if the given file is
already open. The exception Name_Error is propagated if the string
given as Name does not allow the identification of an external
file; in particular, this exception is propagated if no external
file with the given name exists. The exception Use_Error is
propagated if, for the specified mode, the external environment
does not support opening for an external file with the given name
(in the absence of Name_Error) and form.
9 procedure Close(File : in out File_Type);
10 Severs the association between the given file and its associated
external file. The given file is left closed. In addition, for
sequential files, if the file being closed has mode Out_File or
Append_File, then the last element written since the most recent
open or reset is the last element that can be read from the file.
If no elements have been written and the file mode is Out_File,
then the closed file is empty. If no elements have been written
and the file mode is Append_File, then the closed file is
unchanged.
11 The exception Status_Error is propagated if the given file is not
open.
12 procedure Delete(File : in out File_Type);
13 Deletes the external file associated with the given file. The
given file is closed, and the external file ceases to exist.
14 The exception Status_Error is propagated if the given file is not
open. The exception Use_Error is propagated if deletion of the
external file is not supported by the external environment.
15 procedure Reset(File : in out File_Type; Mode : in File_Mode);
procedure Reset(File : in out File_Type);
16/2 {AI95-00085-01} Resets the given file so that reading from its
elements can be restarted from the beginning of the external file
(for modes In_File and Inout_File), and so that writing to its
elements can be restarted at the beginning of the external file
(for modes Out_File and Inout_File) or after the last element of
the external file (for mode Append_File). In particular, for
direct access this means that the current index is set to one. If
a Mode parameter is supplied, the current mode of the given file
is set to the given mode. In addition, for sequential files, if
the given file has mode Out_File or Append_File when Reset is
called, the last element written since the most recent open or
reset is the last element that can be read from the external file.
If no elements have been written and the file mode is Out_File,
the reset file is empty. If no elements have been written and the
file mode is Append_File, then the reset file is unchanged.
17 The exception Status_Error is propagated if the file is not open.
The exception Use_Error is propagated if the external environment
does not support resetting for the external file and, also, if the
external environment does not support resetting to the specified
mode for the external file.
18 function Mode(File : in File_Type) return File_Mode;
19 Returns the current mode of the given file.
20 The exception Status_Error is propagated if the file is not open.
21 function Name(File : in File_Type) return String;
22/2 {AI95-00248-01} Returns a string which uniquely identifies the
external file currently associated with the given file (and may
thus be used in an Open operation).
22.a/2 Discussion: {AI95-00248-01} Retrieving the full path can be
accomplished by passing the result of Name to
Directories.Full_Name (see A.16). It is important to drop the
requirement on Name, as the only way to accomplish this
requirement given that the current directory can be changed with
package Directories is to store the full path when the file is
opened. That's expensive, and it's better for users that need the
full path to explicitly request it.
23 The exception Status_Error is propagated if the given file is not
open. The exception Use_Error is propagated if the associated
external file is a temporary file that cannot be opened by any
name.
24 function Form(File : in File_Type) return String;
25 Returns the form string for the external file currently associated
with the given file. If an external environment allows alternative
specifications of the form (for example, abbreviations using
default options), the string returned by the function should
correspond to a full specification (that is, it should indicate
explicitly all options selected, including default options).
26 The exception Status_Error is propagated if the given file is not
open.
27 function Is_Open(File : in File_Type) return Boolean;
28 Returns True if the file is open (that is, if it is associated
with an external file), otherwise returns False.
Implementation Permissions
29 An implementation may propagate Name_Error or Use_Error if an attempt is
made to use an I/O feature that cannot be supported by the implementation due
to limitations in the external environment. Any such restriction should be
documented.
Wording Changes from Ada 95
29.a/2 {AI95-00085-01} Clarified that Reset affects and depends on the
external file.
29.b/2 {AI95-00248-01} Removed the requirement for Name to return a full
path; this is now accomplished by
Directories.Full_Name(Name(File)) (see A.16). This is not
documented as an inconsistency, because there is no requirement
for implementations to change - the Ada 95 behavior is still
allowed, it just is no longer required.
29.c/2 {AI95-00283-01} Added text to specify the default mode for a
stream file.
A.8.3 Sequential Input-Output Operations
Static Semantics
1 The operations available for sequential input and output are described in
this subclause. The exception Status_Error is propagated if any of these
operations is attempted for a file that is not open.
2 procedure Read(File : in File_Type; Item : out Element_Type);
3 Operates on a file of mode In_File. Reads an element from the
given file, and returns the value of this element in the Item
parameter.
3.a Discussion: We considered basing Sequential_IO.Read on
Element_Type'Read from an implicit stream associated with the
sequential file. However, Element_Type'Read is a type-related
attribute, whereas Sequential_IO should take advantage of the
particular constraints of the actual subtype corresponding to
Element_Type to minimize the size of the external file.
Furthermore, forcing the implementation of Sequential_IO to be
based on Element_Type'Read would create an upward incompatibility
since existing data files written by an Ada 83 program using
Sequential_IO might not be readable by the identical program built
with an Ada 95 implementation of Sequential_IO.
3.b An Ada 95 implementation might still use an implementation-defined
attribute analogous to 'Read to implement the procedure Read, but
that attribute will likely have to be subtype-specific rather than
type-related, and it need not be user-specifiable. Such an
attribute will presumably be needed to implement the generic
package Storage_IO (see A.9).
4 The exception Mode_Error is propagated if the mode is not In_File.
The exception End_Error is propagated if no more elements can be
read from the given file. The exception Data_Error can be
propagated if the element read cannot be interpreted as a value of
the subtype Element_Type (see A.13, "Exceptions in Input-Output
").
4.a Discussion: Data_Error need not be propagated if the check is too
complex. See A.13, "Exceptions in Input-Output".
5 procedure Write(File : in File_Type; Item : in Element_Type);
6 Operates on a file of mode Out_File or Append_File. Writes the
value of Item to the given file.
7 The exception Mode_Error is propagated if the mode is not Out_File
or Append_File. The exception Use_Error is propagated if the
capacity of the external file is exceeded.
8 function End_Of_File(File : in File_Type) return Boolean;
9 Operates on a file of mode In_File. Returns True if no more
elements can be read from the given file; otherwise returns False.
10 The exception Mode_Error is propagated if the mode is not In_File.
A.8.4 The Generic Package Direct_IO
Static Semantics
1 The generic library package Direct_IO has the following declaration:
2 with Ada.IO_Exceptions;
generic
type Element_Type is private;
package Ada.Direct_IO is
3 type File_Type is limited private;
4 type File_Mode is (In_File, Inout_File, Out_File);
type Count is range 0 .. implementation-defined;
subtype Positive_Count is Count range 1 .. Count'Last;
5 -- File management
6 procedure Create(File : in out File_Type;
Mode : in File_Mode := Inout_File;
Name : in String := "";
Form : in String := "");
7 procedure Open (File : in out File_Type;
Mode : in File_Mode;
Name : in String;
Form : in String := "");
8 procedure Close (File : in out File_Type);
procedure Delete(File : in out File_Type);
procedure Reset (File : in out File_Type; Mode : in File_Mode);
procedure Reset (File : in out File_Type);
9 function Mode (File : in File_Type) return File_Mode;
function Name (File : in File_Type) return String;
function Form (File : in File_Type) return String;
10 function Is_Open(File : in File_Type) return Boolean;
11 -- Input and output operations
12 procedure Read (File : in File_Type; Item : out Element_Type;
From : in Positive_Count);
procedure Read (File : in File_Type; Item : out Element_Type);
13 procedure Write(File : in File_Type; Item : in Element_Type;
To : in Positive_Count);
procedure Write(File : in File_Type; Item : in Element_Type);
14 procedure Set_Index(File : in File_Type; To : in Positive_Count);
15 function Index(File : in File_Type) return Positive_Count;
function Size (File : in File_Type) return Count;
16 function End_Of_File(File : in File_Type) return Boolean;
17 -- Exceptions
18 Status_Error : exception renames IO_Exceptions.Status_Error;
Mode_Error : exception renames IO_Exceptions.Mode_Error;
Name_Error : exception renames IO_Exceptions.Name_Error;
Use_Error : exception renames IO_Exceptions.Use_Error;
Device_Error : exception renames IO_Exceptions.Device_Error;
End_Error : exception renames IO_Exceptions.End_Error;
Data_Error : exception renames IO_Exceptions.Data_Error;
19 private
... -- not specified by the language
end Ada.Direct_IO;
19.a Reason: The Element_Type formal of Direct_IO does not have an
unknown_discriminant_part (unlike Sequential_IO) so that the
implementation can make use of the ability to declare
uninitialized variables of the type.
20/2 {AI95-00360-01} The type File_Type needs finalization (see 7.6) in every
instantiation of Direct_IO.
20.a.1/2 This paragraph was deleted.{8652/0097} {AI95-00115-01}
{AI95-00344-01}
Incompatibilities With Ada 95
20.a/2 {AI95-00360-01} {incompatibilities with Ada 95} Amendment
Correction: File_Type in an instance of Direct_IO is defined to
need finalization. If the restriction No_Nested_Finalization (see
D.7) applies to the partition, and File_Type does not have a
controlled part, it will not be allowed in local objects in Ada
2005 whereas it would be allowed in original Ada 95. Such code is
not portable, as another Ada compiler may have a controlled part
in File_Type, and thus would be illegal.
A.8.5 Direct Input-Output Operations
Static Semantics
1 The operations available for direct input and output are described in this
subclause. The exception Status_Error is propagated if any of these operations
is attempted for a file that is not open.
2 procedure Read(File : in File_Type; Item : out Element_Type;
From : in Positive_Count);
procedure Read(File : in File_Type; Item : out Element_Type);
3 Operates on a file of mode In_File or Inout_File. In the case of
the first form, sets the current index of the given file to the
index value given by the parameter From. Then (for both forms)
returns, in the parameter Item, the value of the element whose
position in the given file is specified by the current index of
the file; finally, increases the current index by one.
4 The exception Mode_Error is propagated if the mode of the given
file is Out_File. The exception End_Error is propagated if the
index to be used exceeds the size of the external file. The
exception Data_Error can be propagated if the element read cannot
be interpreted as a value of the subtype Element_Type (see A.13).
5 procedure Write(File : in File_Type; Item : in Element_Type;
To : in Positive_Count);
procedure Write(File : in File_Type; Item : in Element_Type);
6 Operates on a file of mode Inout_File or Out_File. In the case of
the first form, sets the index of the given file to the index
value given by the parameter To. Then (for both forms) gives the
value of the parameter Item to the element whose position in the
given file is specified by the current index of the file; finally,
increases the current index by one.
7 The exception Mode_Error is propagated if the mode of the given
file is In_File. The exception Use_Error is propagated if the
capacity of the external file is exceeded.
8 procedure Set_Index(File : in File_Type; To : in Positive_Count);
9 Operates on a file of any mode. Sets the current index of the
given file to the given index value (which may exceed the current
size of the file).
10 function Index(File : in File_Type) return Positive_Count;
11 Operates on a file of any mode. Returns the current index of the
given file.
12 function Size(File : in File_Type) return Count;
13 Operates on a file of any mode. Returns the current size of the
external file that is associated with the given file.
14 function End_Of_File(File : in File_Type) return Boolean;
15 Operates on a file of mode In_File or Inout_File. Returns True if
the current index exceeds the size of the external file; otherwise
returns False.
16 The exception Mode_Error is propagated if the mode of the given
file is Out_File.
NOTES
17 20 Append_File mode is not supported for the generic package
Direct_IO.
A.9 The Generic Package Storage_IO
1 The generic package Storage_IO provides for reading from and writing to an
in-memory buffer. This generic package supports the construction of
user-defined input-output packages.
1.a Reason: This package exists to allow the portable construction of
user-defined direct-access-oriented input-output packages. The
Write procedure writes a value of type Element_Type into a
Storage_Array of size Buffer_Size, flattening out any implicit
levels of indirection used in the representation of the type. The
Read procedure reads a value of type Element_Type from the buffer,
reconstructing any implicit levels of indirection used in the
representation of the type. It also properly initializes any type
tags that appear within the value, presuming that the buffer was
written by a different program and that tag values for the"
same" type might vary from one executable to another.
Static Semantics
2 The generic library package Storage_IO has the following declaration:
3 with Ada.IO_Exceptions;
with System.Storage_Elements;
generic
type Element_Type is private;
package Ada.Storage_IO is
pragma Preelaborate(Storage_IO);
4 Buffer_Size : constant System.Storage_Elements.Storage_Count :=
implementation-defined;
subtype Buffer_Type is
System.Storage_Elements.Storage_Array(1..Buffer_Size);
5 -- Input and output operations
6 procedure Read (Buffer : in Buffer_Type; Item : out Element_Type);
7 procedure Write(Buffer : out Buffer_Type; Item : in Element_Type);
8 -- Exceptions
9 Data_Error : exception renames IO_Exceptions.Data_Error;
end Ada.Storage_IO;
10 In each instance, the constant Buffer_Size has a value that is the size
(in storage elements) of the buffer required to represent the content of an
object of subtype Element_Type, including any implicit levels of indirection
used by the implementation. The Read and Write procedures of Storage_IO
correspond to the Read and Write procedures of Direct_IO (see A.8.4), but with
the content of the Item parameter being read from or written into the
specified Buffer, rather than an external file.
10.a Reason: As with Direct_IO, the Element_Type formal of Storage_IO
does not have an unknown_discriminant_part so that there is a
well-defined upper bound on the size of the buffer needed to hold
the content of an object of the formal subtype (i.e. Buffer_Size).
If there are no implicit levels of indirection, Buffer_Size will
typically equal:
10.b (Element_Type'Size + System.Storage_Unit - 1) / System.Storage_Unit
10.c Implementation defined: The value of Buffer_Size in Storage_IO.
NOTES
11 21 A buffer used for Storage_IO holds only one element at a time; an
external file used for Direct_IO holds a sequence of elements.
A.10 Text Input-Output
Static Semantics
1 This clause describes the package Text_IO, which provides facilities for
input and output in human-readable form. Each file is read or written
sequentially, as a sequence of characters grouped into lines, and as a
sequence of lines grouped into pages. The specification of the package is
given below in subclause A.10.1.
2 The facilities for file management given above, in subclauses A.8.2 and
A.8.3, are available for text input-output. In place of Read and Write,
however, there are procedures Get and Put that input values of suitable types
from text files, and output values to them. These values are provided to the
Put procedures, and returned by the Get procedures, in a parameter Item.
Several overloaded procedures of these names exist, for different types of
Item. These Get procedures analyze the input sequences of characters based on
lexical elements (see Section 2) and return the corresponding values; the Put
procedures output the given values as appropriate lexical elements. Procedures
Get and Put are also available that input and output individual characters
treated as character values rather than as lexical elements. Related to
character input are procedures to look ahead at the next character without
reading it, and to read a character "immediately" without waiting for an
end-of-line to signal availability.
3 In addition to the procedures Get and Put for numeric and enumeration
types of Item that operate on text files, analogous procedures are provided
that read from and write to a parameter of type String. These procedures
perform the same analysis and composition of character sequences as their
counterparts which have a file parameter.
4 For all Get and Put procedures that operate on text files, and for many
other subprograms, there are forms with and without a file parameter. Each
such Get procedure operates on an input file, and each such Put procedure
operates on an output file. If no file is specified, a default input file or a
default output file is used.
5 {standard input file} {standard output file} At the beginning of program
execution the default input and output files are the so-called standard input
file and standard output file. These files are open, have respectively the
current modes In_File and Out_File, and are associated with two
implementation-defined external files. Procedures are provided to change the
current default input file and the current default output file.
5.a/2 Implementation defined: The external files associated with the
standard input, standard output, and standard error files.
5.a.1/1 Implementation Note: {8652/0113} {AI95-00087-01} The default input
file and default output file are not the names of distinct file
objects, but rather the role played by one or more (other) file
object(s). Thus, they generally will be implemented as accesses to
another file object. An implementation that implements them by
copying them is incorrect.
6 {standard error file} At the beginning of program execution a default file
for program-dependent error-related text output is the so-called standard
error file. This file is open, has the current mode Out_File, and is
associated with an implementation-defined external file. A procedure is
provided to change the current default error file.
7 {line terminator} {page terminator} {file terminator} From a logical point
of view, a text file is a sequence of pages, a page is a sequence of lines,
and a line is a sequence of characters; the end of a line is marked by a line
terminator; the end of a page is marked by the combination of a line
terminator immediately followed by a page terminator; and the end of a file is
marked by the combination of a line terminator immediately followed by a page
terminator and then a file terminator. Terminators are generated during
output; either by calls of procedures provided expressly for that purpose; or
implicitly as part of other operations, for example, when a bounded line
length, a bounded page length, or both, have been specified for a file.
8 The actual nature of terminators is not defined by the language and hence
depends on the implementation. Although terminators are recognized or
generated by certain of the procedures that follow, they are not necessarily
implemented as characters or as sequences of characters. Whether they are
characters (and if so which ones) in any particular implementation need not
concern a user who neither explicitly outputs nor explicitly inputs control
characters. The effect of input (Get) or output (Put) of control characters
(other than horizontal tabulation) is not specified by the language.
{unspecified [partial]}
9 {column number} {current column number} {current line number}
{current page number} The characters of a line are numbered, starting from one;
the number of a character is called its column number. For a line terminator,
a column number is also defined: it is one more than the number of characters
in the line. The lines of a page, and the pages of a file, are similarly
numbered. The current column number is the column number of the next character
or line terminator to be transferred. The current line number is the number of
the current line. The current page number is the number of the current page.
These numbers are values of the subtype Positive_Count of the type Count (by
convention, the value zero of the type Count is used to indicate special
conditions).
10 type Count is range 0 .. implementation-defined;
subtype Positive_Count is Count range 1 .. Count'Last;
11 {maximum line length} {maximum page length} For an output file or an
append file, a maximum line length can be specified and a maximum page length
can be specified. If a value to be output cannot fit on the current line, for
a specified maximum line length, then a new line is automatically started
before the value is output; if, further, this new line cannot fit on the
current page, for a specified maximum page length, then a new page is
automatically started before the value is output. Functions are provided to
determine the maximum line length and the maximum page length. When a file is
opened with mode Out_File or Append_File, both values are zero: by convention,
this means that the line lengths and page lengths are unbounded.
(Consequently, output consists of a single line if the subprograms for
explicit control of line and page structure are not used.) The constant
Unbounded is provided for this purpose.
Extensions to Ada 83
11.a {extensions to Ada 83} Append_File is new in Ada 95.
A.10.1 The Package Text_IO
Static Semantics
1 The library package Text_IO has the following declaration:
2 with Ada.IO_Exceptions;
package Ada.Text_IO is
3 type File_Type is limited private;
4 type File_Mode is (In_File, Out_File, Append_File);
5 type Count is range 0 .. implementation-defined;
subtype Positive_Count is Count range 1 .. Count'Last;
Unbounded : constant Count := 0; -- line and page length
6 subtype Field is Integer range 0 .. implementation-defined;
subtype Number_Base is Integer range 2 .. 16;
7 type Type_Set is (Lower_Case, Upper_Case);
8 -- File Management
9 procedure Create (File : in out File_Type;
Mode : in File_Mode := Out_File;
Name : in String := "";
Form : in String := "");
10 procedure Open (File : in out File_Type;
Mode : in File_Mode;
Name : in String;
Form : in String := "");
11 procedure Close (File : in out File_Type);
procedure Delete (File : in out File_Type);
procedure Reset (File : in out File_Type; Mode : in File_Mode);
procedure Reset (File : in out File_Type);
12 function Mode (File : in File_Type) return File_Mode;
function Name (File : in File_Type) return String;
function Form (File : in File_Type) return String;
13 function Is_Open(File : in File_Type) return Boolean;
14 -- Control of default input and output files
15 procedure Set_Input (File : in File_Type);
procedure Set_Output(File : in File_Type);
procedure Set_Error (File : in File_Type);
16 function Standard_Input return File_Type;
function Standard_Output return File_Type;
function Standard_Error return File_Type;
17 function Current_Input return File_Type;
function Current_Output return File_Type;
function Current_Error return File_Type;
18 type File_Access is access constant File_Type;
19 function Standard_Input return File_Access;
function Standard_Output return File_Access;
function Standard_Error return File_Access;
20 function Current_Input return File_Access;
function Current_Output return File_Access;
function Current_Error return File_Access;
21/1 {8652/0051} {AI95-00057-01} --Buffer control
procedure Flush (File : in File_Type);
procedure Flush;
22 -- Specification of line and page lengths
23 procedure Set_Line_Length(File : in File_Type; To : in Count);
procedure Set_Line_Length(To : in Count);
24 procedure Set_Page_Length(File : in File_Type; To : in Count);
procedure Set_Page_Length(To : in Count);
25 function Line_Length(File : in File_Type) return Count;
function Line_Length return Count;
26 function Page_Length(File : in File_Type) return Count;
function Page_Length return Count;
27 -- Column, Line, and Page Control
28 procedure New_Line (File : in File_Type;
Spacing : in Positive_Count := 1);
procedure New_Line (Spacing : in Positive_Count := 1);
29 procedure Skip_Line (File : in File_Type;
Spacing : in Positive_Count := 1);
procedure Skip_Line (Spacing : in Positive_Count := 1);
30 function End_Of_Line(File : in File_Type) return Boolean;
function End_Of_Line return Boolean;
31 procedure New_Page (File : in File_Type);
procedure New_Page;
32 procedure Skip_Page (File : in File_Type);
procedure Skip_Page;
33 function End_Of_Page(File : in File_Type) return Boolean;
function End_Of_Page return Boolean;
34 function End_Of_File(File : in File_Type) return Boolean;
function End_Of_File return Boolean;
35 procedure Set_Col (File : in File_Type; To : in Positive_Count);
procedure Set_Col (To : in Positive_Count);
36 procedure Set_Line(File : in File_Type; To : in Positive_Count);
procedure Set_Line(To : in Positive_Count);
37 function Col (File : in File_Type) return Positive_Count;
function Col return Positive_Count;
38 function Line(File : in File_Type) return Positive_Count;
function Line return Positive_Count;
39 function Page(File : in File_Type) return Positive_Count;
function Page return Positive_Count;
40 -- Character Input-Output
41 procedure Get(File : in File_Type; Item : out Character);
procedure Get(Item : out Character);
42 procedure Put(File : in File_Type; Item : in Character);
procedure Put(Item : in Character);
43 procedure Look_Ahead (File : in File_Type;
Item : out Character;
End_Of_Line : out Boolean);
procedure Look_Ahead (Item : out Character;
End_Of_Line : out Boolean);
44 procedure Get_Immediate(File : in File_Type;
Item : out Character);
procedure Get_Immediate(Item : out Character);
45 procedure Get_Immediate(File : in File_Type;
Item : out Character;
Available : out Boolean);
procedure Get_Immediate(Item : out Character;
Available : out Boolean);
46 -- String Input-Output
47 procedure Get(File : in File_Type; Item : out String);
procedure Get(Item : out String);
48 procedure Put(File : in File_Type; Item : in String);
procedure Put(Item : in String);
49 procedure Get_Line(File : in File_Type;
Item : out String;
Last : out Natural);
procedure Get_Line(Item : out String; Last : out Natural);
49.1/2 {AI95-00301-01} function Get_Line
(File : in File_Type) return String;
function Get_Line return String;
50 procedure Put_Line(File : in File_Type; Item : in String);
procedure Put_Line(Item : in String);
51 -- Generic packages for Input-Output of Integer Types
52 generic
type Num is range <>;
package Integer_IO is
53 Default_Width : Field := Num'Width;
Default_Base : Number_Base := 10;
54 procedure Get(File : in File_Type;
Item : out Num;
Width : in Field := 0);
procedure Get(Item : out Num;
Width : in Field := 0);
55 procedure Put(File : in File_Type;
Item : in Num;
Width : in Field := Default_Width;
Base : in Number_Base := Default_Base);
procedure Put(Item : in Num;
Width : in Field := Default_Width;
Base : in Number_Base := Default_Base);
procedure Get(From : in String;
Item : out Num;
Last : out Positive);
procedure Put(To : out String;
Item : in Num;
Base : in Number_Base := Default_Base);
56 end Integer_IO;
57 generic
type Num is mod <>;
package Modular_IO is
58 Default_Width : Field := Num'Width;
Default_Base : Number_Base := 10;
59 procedure Get(File : in File_Type;
Item : out Num;
Width : in Field := 0);
procedure Get(Item : out Num;
Width : in Field := 0);
60 procedure Put(File : in File_Type;
Item : in Num;
Width : in Field := Default_Width;
Base : in Number_Base := Default_Base);
procedure Put(Item : in Num;
Width : in Field := Default_Width;
Base : in Number_Base := Default_Base);
procedure Get(From : in String;
Item : out Num;
Last : out Positive);
procedure Put(To : out String;
Item : in Num;
Base : in Number_Base := Default_Base);
61 end Modular_IO;
62 -- Generic packages for Input-Output of Real Types
63 generic
type Num is digits <>;
package Float_IO is
64 Default_Fore : Field := 2;
Default_Aft : Field := Num'Digits-1;
Default_Exp : Field := 3;
65 procedure Get(File : in File_Type;
Item : out Num;
Width : in Field := 0);
procedure Get(Item : out Num;
Width : in Field := 0);
66 procedure Put(File : in File_Type;
Item : in Num;
Fore : in Field := Default_Fore;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
procedure Put(Item : in Num;
Fore : in Field := Default_Fore;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
67 procedure Get(From : in String;
Item : out Num;
Last : out Positive);
procedure Put(To : out String;
Item : in Num;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
end Float_IO;
68 generic
type Num is delta <>;
package Fixed_IO is
69 Default_Fore : Field := Num'Fore;
Default_Aft : Field := Num'Aft;
Default_Exp : Field := 0;
70 procedure Get(File : in File_Type;
Item : out Num;
Width : in Field := 0);
procedure Get(Item : out Num;
Width : in Field := 0);
71 procedure Put(File : in File_Type;
Item : in Num;
Fore : in Field := Default_Fore;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
procedure Put(Item : in Num;
Fore : in Field := Default_Fore;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
72 procedure Get(From : in String;
Item : out Num;
Last : out Positive);
procedure Put(To : out String;
Item : in Num;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
end Fixed_IO;
73 generic
type Num is delta <> digits <>;
package Decimal_IO is
74 Default_Fore : Field := Num'Fore;
Default_Aft : Field := Num'Aft;
Default_Exp : Field := 0;
75 procedure Get(File : in File_Type;
Item : out Num;
Width : in Field := 0);
procedure Get(Item : out Num;
Width : in Field := 0);
76 procedure Put(File : in File_Type;
Item : in Num;
Fore : in Field := Default_Fore;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
procedure Put(Item : in Num;
Fore : in Field := Default_Fore;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
77 procedure Get(From : in String;
Item : out Num;
Last : out Positive);
procedure Put(To : out String;
Item : in Num;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
end Decimal_IO;
78 -- Generic package for Input-Output of Enumeration Types
79 generic
type Enum is (<>);
package Enumeration_IO is
80 Default_Width : Field := 0;
Default_Setting : Type_Set := Upper_Case;
81 procedure Get(File : in File_Type;
Item : out Enum);
procedure Get(Item : out Enum);
82 procedure Put(File : in File_Type;
Item : in Enum;
Width : in Field := Default_Width;
Set : in Type_Set := Default_Setting);
procedure Put(Item : in Enum;
Width : in Field := Default_Width;
Set : in Type_Set := Default_Setting);
83 procedure Get(From : in String;
Item : out Enum;
Last : out Positive);
procedure Put(To : out String;
Item : in Enum;
Set : in Type_Set := Default_Setting);
end Enumeration_IO;
84 -- Exceptions
85 Status_Error : exception renames IO_Exceptions.Status_Error;
Mode_Error : exception renames IO_Exceptions.Mode_Error;
Name_Error : exception renames IO_Exceptions.Name_Error;
Use_Error : exception renames IO_Exceptions.Use_Error;
Device_Error : exception renames IO_Exceptions.Device_Error;
End_Error : exception renames IO_Exceptions.End_Error;
Data_Error : exception renames IO_Exceptions.Data_Error;
Layout_Error : exception renames IO_Exceptions.Layout_Error;
private
... -- not specified by the language
end Ada.Text_IO;
86/2 {AI95-00360-01} The type File_Type needs finalization (see 7.6).
Incompatibilities With Ada 83
86.a {incompatibilities with Ada 83} Append_File is a new element of
enumeration type File_Mode.
Extensions to Ada 83
86.b {extensions to Ada 83} Get_Immediate, Look_Ahead, the subprograms
for dealing with standard error, the type File_Access and its
associated subprograms, and the generic packages Modular_IO and
Decimal_IO are new in Ada 95.
Incompatibilities With Ada 95
86.c/2 {AI95-00360-01} {incompatibilities with Ada 95} Amendment
Correction: Text_IO.File_Type is defined to need finalization. If
the restriction No_Nested_Finalization (see D.7) applies to the
partition, and File_Type does not have a controlled part, it will
not be allowed in local objects in Ada 2005 whereas it would be
allowed in original Ada 95. Such code is not portable, as another
Ada compiler may have a controlled part in File_Type, and thus
would be illegal.
Wording Changes from Ada 95
86.d/2 {8652/0051} {AI95-00057-01} Corrigendum: Corrected the parameter
mode of Flush; otherwise it could not be used on Standard_Output.
86.e/2 {AI95-00301-01} The Text_IO.Get_Line functions are new; they are
described in A.10.7, "Input-Output of Characters and Strings".
A.10.2 Text File Management
Static Semantics
1 The only allowed file modes for text files are the modes In_File,
Out_File, and Append_File. The subprograms given in subclause A.8.2 for the
control of external files, and the function End_Of_File given in subclause
A.8.3 for sequential input-output, are also available for text files. There is
also a version of End_Of_File that refers to the current default input file.
For text files, the procedures have the following additional effects:
2 * For the procedures Create and Open: After a file with mode Out_File or
Append_File is opened, the page length and line length are unbounded
(both have the conventional value zero). After a file (of any mode) is
opened, the current column, current line, and current page numbers are
set to one. If the mode is Append_File, it is implementation defined
whether a page terminator will separate preexisting text in the file
from the new text to be written.
2.a Reason: For a file with mode Append_File, although it may seem
more sensible for Open to set the current column, line, and page
number based on the number of pages in the file, the number of
lines on the last page, and the number of columns in the last
line, we rejected this approach because of implementation costs;
it would require the implementation to scan the file before doing
the append, or to do processing that would be equivalent in effect.
2.b For similar reasons, there is no requirement to erase the last
page terminator of the file, nor to insert an explicit page
terminator in the case when the final page terminator of a file is
represented implicitly by the implementation.
3 * For the procedure Close: If the file has the current mode Out_File or
Append_File, has the effect of calling New_Page, unless the current
page is already terminated; then outputs a file terminator.
4 * For the procedure Reset: If the file has the current mode Out_File or
Append_File, has the effect of calling New_Page, unless the current
page is already terminated; then outputs a file terminator. The
current column, line, and page numbers are set to one, and the line
and page lengths to Unbounded. If the new mode is Append_File, it is
implementation defined whether a page terminator will separate
preexisting text in the file from the new text to be written.
4.a Reason: The behavior of Reset should be similar to closing a file
and reopening it with the given mode
5 The exception Mode_Error is propagated by the procedure Reset upon an
attempt to change the mode of a file that is the current default input file,
the current default output file, or the current default error file.
NOTES
6 22 An implementation can define the Form parameter of Create and Open
to control effects including the following:
7 * the interpretation of line and column numbers for an interactive
file, and
8 * the interpretation of text formats in a file created by a foreign
program.
A.10.3 Default Input, Output, and Error Files
Static Semantics
1 The following subprograms provide for the control of the particular
default files that are used when a file parameter is omitted from a Get, Put,
or other operation of text input-output described below, or when
application-dependent error-related text is to be output.
2 procedure Set_Input(File : in File_Type);
3 Operates on a file of mode In_File. Sets the current default input
file to File.
4 The exception Status_Error is propagated if the given file is not
open. The exception Mode_Error is propagated if the mode of the
given file is not In_File.
5 procedure Set_Output(File : in File_Type);
procedure Set_Error (File : in File_Type);
6 Each operates on a file of mode Out_File or Append_File.
Set_Output sets the current default output file to File. Set_Error
sets the current default error file to File. The exception
Status_Error is propagated if the given file is not open. The
exception Mode_Error is propagated if the mode of the given file
is not Out_File or Append_File.
7 function Standard_Input return File_Type;
function Standard_Input return File_Access;
8 Returns the standard input file (see A.10), or an access value
designating the standard input file, respectively.
9 function Standard_Output return File_Type;
function Standard_Output return File_Access;
10 Returns the standard output file (see A.10) or an access value
designating the standard output file, respectively.
11 function Standard_Error return File_Type;
function Standard_Error return File_Access;
12/1 {8652/0052} {AI95-00194-01} Returns the standard error file (see
A.10), or an access value designating the standard error file,
respectively.
13 The Form strings implicitly associated with the opening of Standard_Input,
Standard_Output, and Standard_Error at the start of program execution are
implementation defined.
14 function Current_Input return File_Type;
function Current_Input return File_Access;
15 Returns the current default input file, or an access value
designating the current default input file, respectively.
16 function Current_Output return File_Type;
function Current_Output return File_Access;
17 Returns the current default output file, or an access value
designating the current default output file, respectively.
18 function Current_Error return File_Type;
function Current_Error return File_Access;
19 Returns the current default error file, or an access value
designating the current default error file, respectively.
20/1 {8652/0051} {AI95-00057-01} procedure Flush (File : in File_Type);
procedure Flush;
21 The effect of Flush is the same as the corresponding subprogram in
Streams.Stream_IO (see A.12.1). If File is not explicitly
specified, Current_Output is used.
Erroneous Execution
22/1 {8652/0053} {AI95-00063-01} {erroneous execution (cause) [partial]} The
execution of a program is erroneous if it invokes an operation on a current
default input, default output, or default error file, and if the corresponding
file object is closed or no longer exists.
22.a.1/1 Ramification: {8652/0053} {AI95-00063-01} Closing a default file,
then setting the default file to another open file before
accessing it is not erroneous.
23/1 This paragraph was deleted.{8652/0053} {AI95-00063-01}
NOTES
24 23 The standard input, standard output, and standard error files
cannot be opened, closed, reset, or deleted, because the parameter
File of the corresponding procedures has the mode in out.
25 24 The standard input, standard output, and standard error files are
different file objects, but not necessarily different external files.
Wording Changes from Ada 95
25.a/2 {8652/0051} {AI95-00057-01} Corrigendum: Corrected the parameter
mode of Flush; otherwise it could not be used on Standard_Output.
25.b/2 {8652/0052} {AI95-00194-01} Corrigendum: Corrected Standard_Error
so it refers to the correct file.
25.c/2 {8652/0053} {AI95-00063-01} Corrigendum: Clarified that execution
is erroneous only when a closed default file is accessed.
A.10.4 Specification of Line and Page Lengths
Static Semantics
1 The subprograms described in this subclause are concerned with the line
and page structure of a file of mode Out_File or Append_File. They operate
either on the file given as the first parameter, or, in the absence of such a
file parameter, on the current default output file. They provide for output of
text with a specified maximum line length or page length. In these cases, line
and page terminators are output implicitly and automatically when needed. When
line and page lengths are unbounded (that is, when they have the conventional
value zero), as in the case of a newly opened file, new lines and new pages
are only started when explicitly called for.
2 In all cases, the exception Status_Error is propagated if the file to be
used is not open; the exception Mode_Error is propagated if the mode of the
file is not Out_File or Append_File.
3 procedure Set_Line_Length(File : in File_Type; To : in Count);
procedure Set_Line_Length(To : in Count);
4 Sets the maximum line length of the specified output or append
file to the number of characters specified by To. The value zero
for To specifies an unbounded line length.
4.a Ramification: The setting does not affect the lengths of lines in
the existing file, rather it only influences subsequent output
operations.
5 The exception Use_Error is propagated if the specified line length
is inappropriate for the associated external file.
6 procedure Set_Page_Length(File : in File_Type; To : in Count);
procedure Set_Page_Length(To : in Count);
7 Sets the maximum page length of the specified output or append
file to the number of lines specified by To. The value zero for To
specifies an unbounded page length.
8 The exception Use_Error is propagated if the specified page length
is inappropriate for the associated external file.
9 function Line_Length(File : in File_Type) return Count;
function Line_Length return Count;
10 Returns the maximum line length currently set for the specified
output or append file, or zero if the line length is unbounded.
11 function Page_Length(File : in File_Type) return Count;
function Page_Length return Count;
12 Returns the maximum page length currently set for the specified
output or append file, or zero if the page length is unbounded.
A.10.5 Operations on Columns, Lines, and Pages
Static Semantics
1 The subprograms described in this subclause provide for explicit control
of line and page structure; they operate either on the file given as the first
parameter, or, in the absence of such a file parameter, on the appropriate
(input or output) current default file. The exception Status_Error is
propagated by any of these subprograms if the file to be used is not open.
2 procedure New_Line(File : in File_Type; Spacing : in Positive_Count := 1);
procedure New_Line(Spacing : in Positive_Count := 1);
3 Operates on a file of mode Out_File or Append_File.
4 For a Spacing of one: Outputs a line terminator and sets the
current column number to one. Then increments the current line
number by one, except in the case that the current line number is
already greater than or equal to the maximum page length, for a
bounded page length; in that case a page terminator is output, the
current page number is incremented by one, and the current line
number is set to one.
5 For a Spacing greater than one, the above actions are performed
Spacing times.
6 The exception Mode_Error is propagated if the mode is not Out_File
or Append_File.
7 procedure Skip_Line(File : in File_Type; Spacing : in Positive_Count := 1);
procedure Skip_Line(Spacing : in Positive_Count := 1);
8 Operates on a file of mode In_File.
9 For a Spacing of one: Reads and discards all characters until a
line terminator has been read, and then sets the current column
number to one. If the line terminator is not immediately followed
by a page terminator, the current line number is incremented by
one. Otherwise, if the line terminator is immediately followed by
a page terminator, then the page terminator is skipped, the
current page number is incremented by one, and the current line
number is set to one.
10 For a Spacing greater than one, the above actions are performed
Spacing times.
11 The exception Mode_Error is propagated if the mode is not In_File.
The exception End_Error is propagated if an attempt is made to
read a file terminator.
12 function End_Of_Line(File : in File_Type) return Boolean;
function End_Of_Line return Boolean;
13 Operates on a file of mode In_File. Returns True if a line
terminator or a file terminator is next; otherwise returns False.
14 The exception Mode_Error is propagated if the mode is not In_File.
15 procedure New_Page(File : in File_Type);
procedure New_Page;
16 Operates on a file of mode Out_File or Append_File. Outputs a line
terminator if the current line is not terminated, or if the
current page is empty (that is, if the current column and line
numbers are both equal to one). Then outputs a page terminator,
which terminates the current page. Adds one to the current page
number and sets the current column and line numbers to one.
17 The exception Mode_Error is propagated if the mode is not Out_File
or Append_File.
18 procedure Skip_Page(File : in File_Type);
procedure Skip_Page;
19 Operates on a file of mode In_File. Reads and discards all
characters and line terminators until a page terminator has been
read. Then adds one to the current page number, and sets the
current column and line numbers to one.
20 The exception Mode_Error is propagated if the mode is not In_File.
The exception End_Error is propagated if an attempt is made to
read a file terminator.
21 function End_Of_Page(File : in File_Type) return Boolean;
function End_Of_Page return Boolean;
22 Operates on a file of mode In_File. Returns True if the
combination of a line terminator and a page terminator is next, or
if a file terminator is next; otherwise returns False.
23 The exception Mode_Error is propagated if the mode is not In_File.
24 function End_Of_File(File : in File_Type) return Boolean;
function End_Of_File return Boolean;
25 Operates on a file of mode In_File. Returns True if a file
terminator is next, or if the combination of a line, a page, and a
file terminator is next; otherwise returns False.
26 The exception Mode_Error is propagated if the mode is not In_File.
27 The following subprograms provide for the control of the current position
of reading or writing in a file. In all cases, the default file is the current
output file.
28 procedure Set_Col(File : in File_Type; To : in Positive_Count);
procedure Set_Col(To : in Positive_Count);
29 If the file mode is Out_File or Append_File:
30 * If the value specified by To is greater than the current
column number, outputs spaces, adding one to the current
column number after each space, until the current column
number equals the specified value. If the value specified by
To is equal to the current column number, there is no effect.
If the value specified by To is less than the current column
number, has the effect of calling New_Line (with a spacing of
one), then outputs (To - 1) spaces, and sets the current
column number to the specified value.
31 * The exception Layout_Error is propagated if the value
specified by To exceeds Line_Length when the line length is
bounded (that is, when it does not have the conventional value
zero).
32 If the file mode is In_File:
33 * Reads (and discards) individual characters, line terminators,
and page terminators, until the next character to be read has
a column number that equals the value specified by To; there
is no effect if the current column number already equals this
value. Each transfer of a character or terminator maintains
the current column, line, and page numbers in the same way as
a Get procedure (see A.10.6). (Short lines will be skipped
until a line is reached that has a character at the specified
column position.)
34 * The exception End_Error is propagated if an attempt is made to
read a file terminator.
35 procedure Set_Line(File : in File_Type; To : in Positive_Count);
procedure Set_Line(To : in Positive_Count);
36 If the file mode is Out_File or Append_File:
37 * If the value specified by To is greater than the current line
number, has the effect of repeatedly calling New_Line (with a
spacing of one), until the current line number equals the
specified value. If the value specified by To is equal to the
current line number, there is no effect. If the value
specified by To is less than the current line number, has the
effect of calling New_Page followed by a call of New_Line with
a spacing equal to (To - 1).
38 * The exception Layout_Error is propagated if the value
specified by To exceeds Page_Length when the page length is
bounded (that is, when it does not have the conventional value
zero).
39 If the mode is In_File:
40 * Has the effect of repeatedly calling Skip_Line (with a spacing
of one), until the current line number equals the value
specified by To; there is no effect if the current line number
already equals this value. (Short pages will be skipped until
a page is reached that has a line at the specified line
position.)
41 * The exception End_Error is propagated if an attempt is made to
read a file terminator.
42 function Col(File : in File_Type) return Positive_Count;
function Col return Positive_Count;
43 Returns the current column number.
44 The exception Layout_Error is propagated if this number exceeds
Count'Last.
45 function Line(File : in File_Type) return Positive_Count;
function Line return Positive_Count;
46 Returns the current line number.
47 The exception Layout_Error is propagated if this number exceeds
Count'Last.
48 function Page(File : in File_Type) return Positive_Count;
function Page return Positive_Count;
49 Returns the current page number.
50 The exception Layout_Error is propagated if this number exceeds
Count'Last.
51 The column number, line number, or page number are allowed to exceed
Count'Last (as a consequence of the input or output of sufficiently many
characters, lines, or pages). These events do not cause any exception to be
propagated. However, a call of Col, Line, or Page propagates the exception
Layout_Error if the corresponding number exceeds Count'Last.
NOTES
52 25 A page terminator is always skipped whenever the preceding line
terminator is skipped. An implementation may represent the combination
of these terminators by a single character, provided that it is
properly recognized on input.
A.10.6 Get and Put Procedures
Static Semantics
1 The procedures Get and Put for items of the type Character, String,
numeric types, and enumeration types are described in subsequent subclauses.
Features of these procedures that are common to most of these types are
described in this subclause. The Get and Put procedures for items of type
Character and String deal with individual character values; the Get and Put
procedures for numeric and enumeration types treat the items as lexical
elements.
2 All procedures Get and Put have forms with a file parameter, written
first. Where this parameter is omitted, the appropriate (input or output)
current default file is understood to be specified. Each procedure Get
operates on a file of mode In_File. Each procedure Put operates on a file of
mode Out_File or Append_File.
3 All procedures Get and Put maintain the current column, line, and page
numbers of the specified file: the effect of each of these procedures upon
these numbers is the result of the effects of individual transfers of
characters and of individual output or skipping of terminators. Each transfer
of a character adds one to the current column number. Each output of a line
terminator sets the current column number to one and adds one to the current
line number. Each output of a page terminator sets the current column and line
numbers to one and adds one to the current page number. For input, each
skipping of a line terminator sets the current column number to one and adds
one to the current line number; each skipping of a page terminator sets the
current column and line numbers to one and adds one to the current page
number. Similar considerations apply to the procedures Get_Line, Put_Line, and
Set_Col.
4 Several Get and Put procedures, for numeric and enumeration types, have
format parameters which specify field lengths; these parameters are of the
nonnegative subtype Field of the type Integer.
5/2 {AI95-00223-01} {blank (in text input for enumeration and numeric types)}
Input-output of enumeration values uses the syntax of the corresponding
lexical elements. Any Get procedure for an enumeration type begins by skipping
any leading blanks, or line or page terminators. A blank is defined as a space
or a horizontal tabulation character. Next, characters are input only so long
as the sequence input is an initial sequence of an identifier or of a
character literal (in particular, input ceases when a line terminator is
encountered). The character or line terminator that causes input to cease
remains available for subsequent input.
6 For a numeric type, the Get procedures have a format parameter called
Width. If the value given for this parameter is zero, the Get procedure
proceeds in the same manner as for enumeration types, but using the syntax of
numeric literals instead of that of enumeration literals. If a nonzero value
is given, then exactly Width characters are input, or the characters up to a
line terminator, whichever comes first; any skipped leading blanks are
included in the count. The syntax used for numeric literals is an extended
syntax that allows a leading sign (but no intervening blanks, or line or page
terminators) and that also allows (for real types) an integer literal as well
as forms that have digits only before the point or only after the point.
7 Any Put procedure, for an item of a numeric or an enumeration type,
outputs the value of the item as a numeric literal, identifier, or character
literal, as appropriate. This is preceded by leading spaces if required by the
format parameters Width or Fore (as described in later subclauses), and then a
minus sign for a negative value; for an enumeration type, the spaces follow
instead of leading. The format given for a Put procedure is overridden if it
is insufficiently wide, by using the minimum needed width.
8 Two further cases arise for Put procedures for numeric and enumeration
types, if the line length of the specified output file is bounded (that is, if
it does not have the conventional value zero). If the number of characters to
be output does not exceed the maximum line length, but is such that they
cannot fit on the current line, starting from the current column, then (in
effect) New_Line is called (with a spacing of one) before output of the item.
Otherwise, if the number of characters exceeds the maximum line length, then
the exception Layout_Error is propagated and nothing is output.
9 The exception Status_Error is propagated by any of the procedures Get,
Get_Line, Put, and Put_Line if the file to be used is not open. The exception
Mode_Error is propagated by the procedures Get and Get_Line if the mode of the
file to be used is not In_File; and by the procedures Put and Put_Line, if the
mode is not Out_File or Append_File.
10 The exception End_Error is propagated by a Get procedure if an attempt is
made to skip a file terminator. The exception Data_Error is propagated by a
Get procedure if the sequence finally input is not a lexical element
corresponding to the type, in particular if no characters were input; for this
test, leading blanks are ignored; for an item of a numeric type, when a sign
is input, this rule applies to the succeeding numeric literal. The exception
Layout_Error is propagated by a Put procedure that outputs to a parameter of
type String, if the length of the actual string is insufficient for the output
of the item.
Examples
11 In the examples, here and in subclauses A.10.8 and A.10.9, the string
quotes and the lower case letter b are not transferred: they are shown only to
reveal the layout and spaces.
12 N : Integer;
...
Get(N);
13 -- Characters at input Sequence input
Value of N
-- bb-12535b -12535 -12535
-- bb12_535e1b 12_535e1 125350
-- bb12_535e; 12_535e
(none) Data_Error raised
14 Example of overridden width parameter:
15 Put(Item => -23, Width => 2); -- "-23"
Wording Changes from Ada 95
15.a/2 {AI95-00223-01} Removed conflicting text describing the skipping
of blanks for a Get procedure.
A.10.7 Input-Output of Characters and Strings
Static Semantics
1 For an item of type Character the following procedures are provided:
2 procedure Get(File : in File_Type; Item : out Character);
procedure Get(Item : out Character);
3 After skipping any line terminators and any page terminators,
reads the next character from the specified input file and returns
the value of this character in the out parameter Item.
4 The exception End_Error is propagated if an attempt is made to
skip a file terminator.
5 procedure Put(File : in File_Type; Item : in Character);
procedure Put(Item : in Character);
6 If the line length of the specified output file is bounded (that
is, does not have the conventional value zero), and the current
column number exceeds it, has the effect of calling New_Line with
a spacing of one. Then, or otherwise, outputs the given character
to the file.
7 procedure Look_Ahead (File : in File_Type;
Item : out Character;
End_Of_Line : out Boolean);
procedure Look_Ahead (Item : out Character;
End_Of_Line : out Boolean);
8/1 Mode_Error is propagated if the mode of the file is not In_File.
Sets End_Of_Line to True if at end of line, including if at end of
page or at end of file; in each of these cases the value of Item
is not specified. {unspecified [partial]} Otherwise End_Of_Line is
set to False and Item is set to the next character (without
consuming it) from the file.
9 procedure Get_Immediate(File : in File_Type;
Item : out Character);
procedure Get_Immediate(Item : out Character);
10 Reads the next character, either control or graphic, from the
specified File or the default input file. Mode_Error is propagated
if the mode of the file is not In_File. End_Error is propagated if
at the end of the file. The current column, line and page numbers
for the file are not affected.
11 procedure Get_Immediate(File : in File_Type;
Item : out Character;
Available : out Boolean);
procedure Get_Immediate(Item : out Character;
Available : out Boolean);
12 If a character, either control or graphic, is available from the
specified File or the default input file, then the character is
read; Available is True and Item contains the value of this
character. If a character is not available, then Available is
False and the value of Item is not specified. {unspecified
[partial]} Mode_Error is propagated if the mode of the file is
not In_File. End_Error is propagated if at the end of the file.
The current column, line and page numbers for the file are not
affected.
13/2 {AI95-00301-01} For an item of type String the following subprograms are
provided:
14 procedure Get(File : in File_Type; Item : out String);
procedure Get(Item : out String);
15 Determines the length of the given string and attempts that number
of Get operations for successive characters of the string (in
particular, no operation is performed if the string is null).
16 procedure Put(File : in File_Type; Item : in String);
procedure Put(Item : in String);
17 Determines the length of the given string and attempts that number
of Put operations for successive characters of the string (in
particular, no operation is performed if the string is null).
17.1/2 function Get_Line(File : in File_Type) return String;
function Get_Line return String;
17.2/2 {AI95-00301-01} Returns a result string constructed by reading
successive characters from the specified input file, and assigning
them to successive characters of the result string. The result
string has a lower bound of 1 and an upper bound of the number of
characters read. Reading stops when the end of the line is met;
Skip_Line is then (in effect) called with a spacing of 1.
17.3/2 {AI95-00301-01} Constraint_Error is raised if the length of the
line exceeds Positive'Last; in this case, the line number and page
number are unchanged, and the column number is unspecified but no
less than it was before the call.{unspecified [partial]} The
exception End_Error is propagated if an attempt is made to skip a
file terminator.
17.a/2 Ramification: {AI95-00301-01} Precisely what is left in the file
is unspecified if Constraint_Error is raised because the line
doesn't fit in a String; it should be consistent with column
number. This allows implementers to use whatever buffering scheme
makes sense. But the line terminator is not skipped in this case.
18 procedure Get_Line(File : in File_Type;
Item : out String;
Last : out Natural);
procedure Get_Line(Item : out String; Last : out Natural);
19 Reads successive characters from the specified input file and
assigns them to successive characters of the specified string.
Reading stops if the end of the string is met. Reading also stops
if the end of the line is met before meeting the end of the
string; in this case Skip_Line is (in effect) called with a
spacing of 1. {unspecified [partial]} The values of characters not
assigned are not specified.
20 If characters are read, returns in Last the index value such that
Item(Last) is the last character assigned (the index of the first
character assigned is Item'First). If no characters are read,
returns in Last an index value that is one less than Item'First.
The exception End_Error is propagated if an attempt is made to
skip a file terminator.
21 procedure Put_Line(File : in File_Type; Item : in String);
procedure Put_Line(Item : in String);
22 Calls the procedure Put for the given string, and then the
procedure New_Line with a spacing of one.
Implementation Advice
23 The Get_Immediate procedures should be implemented with unbuffered input.
For a device such as a keyboard, input should be "available" if a key has
already been typed, whereas for a disk file, input should always be available
except at end of file. For a file associated with a keyboard-like device, any
line-editing features of the underlying operating system should be disabled
during the execution of Get_Immediate.
23.a/2 Implementation Advice: Get_Immediate should be implemented with
unbuffered input; input should be available immediately;
line-editing should be disabled.
NOTES
24 26 Get_Immediate can be used to read a single key from the keyboard
"immediately"; that is, without waiting for an end of line. In a call
of Get_Immediate without the parameter Available, the caller will wait
until a character is available.
25 27 In a literal string parameter of Put, the enclosing string bracket
characters are not output. Each doubled string bracket character in
the enclosed string is output as a single string bracket character, as
a consequence of the rule for string literals (see 2.6).
26 28 A string read by Get or written by Put can extend over several
lines. An implementation is allowed to assume that certain external
files do not contain page terminators, in which case Get_Line and
Skip_Line can return as soon as a line terminator is read.
Incompatibilities With Ada 95
26.a/2 {AI95-00301-01} {incompatibilities with Ada 95} The Get_Line
functions are newly added to Ada.Text_IO. If Ada.Text_IO is
referenced in a use_clause, and a function Get_Line is defined in
a package that is also referenced in a use_clause, the
user-defined Get_Line may no longer be use-visible, resulting in
errors. This should be rare and is easily fixed if it does occur.
Extensions to Ada 95
26.b/2 {AI95-00301-01} {extensions to Ada 95} The Text_IO.Get_Line
functions are new.
A.10.8 Input-Output for Integer Types
Static Semantics
1 The following procedures are defined in the generic packages Integer_IO
and Modular_IO, which have to be instantiated for the appropriate signed
integer or modular type respectively (indicated by Num in the specifications).
2 Values are output as decimal or based literals, without low line
characters or exponent, and, for Integer_IO, preceded by a minus sign if
negative. The format (which includes any leading spaces and minus sign) can be
specified by an optional field width parameter. Values of widths of fields in
output formats are of the nonnegative integer subtype Field. Values of bases
are of the integer subtype Number_Base.
3 subtype Number_Base is Integer range 2 .. 16;
4 The default field width and base to be used by output procedures are
defined by the following variables that are declared in the generic packages
Integer_IO and Modular_IO:
5 Default_Width : Field := Num'Width;
Default_Base : Number_Base := 10;
6 The following procedures are provided:
7 procedure Get(File : in File_Type; Item : out Num; Width : in Field := 0);
procedure Get(Item : out Num; Width : in Field := 0);
8 If the value of the parameter Width is zero, skips any leading
blanks, line terminators, or page terminators, then reads a plus
sign if present or (for a signed type only) a minus sign if
present, then reads the longest possible sequence of characters
matching the syntax of a numeric literal without a point. If a
nonzero value of Width is supplied, then exactly Width characters
are input, or the characters (possibly none) up to a line
terminator, whichever comes first; any skipped leading blanks are
included in the count.
9 Returns, in the parameter Item, the value of type Num that
corresponds to the sequence input.
10 The exception Data_Error is propagated if the sequence of
characters read does not form a legal integer literal or if the
value obtained is not of the subtype Num (for Integer_IO) or is
not in the base range of Num (for Modular_IO).
11 procedure Put(File : in File_Type;
Item : in Num;
Width : in Field := Default_Width;
Base : in Number_Base := Default_Base);
procedure Put(Item : in Num;
Width : in Field := Default_Width;
Base : in Number_Base := Default_Base);
12 Outputs the value of the parameter Item as an integer literal,
with no low lines, no exponent, and no leading zeros (but a single
zero for the value zero), and a preceding minus sign for a
negative value.
13 If the resulting sequence of characters to be output has fewer
than Width characters, then leading spaces are first output to
make up the difference.
14 Uses the syntax for decimal literal if the parameter Base has the
value ten (either explicitly or through Default_Base); otherwise,
uses the syntax for based literal, with any letters in upper case.
15 procedure Get(From : in String; Item : out Num; Last : out Positive);
16 Reads an integer value from the beginning of the given string,
following the same rules as the Get procedure that reads an
integer value from a file, but treating the end of the string as a
file terminator. Returns, in the parameter Item, the value of type
Num that corresponds to the sequence input. Returns in Last the
index value such that From(Last) is the last character read.
17 The exception Data_Error is propagated if the sequence input does
not have the required syntax or if the value obtained is not of
the subtype Num.
18 procedure Put(To : out String;
Item : in Num;
Base : in Number_Base := Default_Base);
19 Outputs the value of the parameter Item to the given string,
following the same rule as for output to a file, using the length
of the given string as the value for Width.
20 Integer_Text_IO is a library package that is a nongeneric equivalent to
Text_IO.Integer_IO for the predefined type Integer:
21 with Ada.Text_IO;
package Ada.Integer_Text_IO is new Ada.Text_IO.Integer_IO(Integer);
22 For each predefined signed integer type, a nongeneric equivalent to
Text_IO.Integer_IO is provided, with names such as Ada.Long_Integer_Text_IO.
Implementation Permissions
23 The nongeneric equivalent packages may, but need not, be actual
instantiations of the generic package for the appropriate predefined type.
NOTES
24 29 For Modular_IO, execution of Get propagates Data_Error if the
sequence of characters read forms an integer literal outside the range
0..Num'Last.
Examples
25/1 This paragraph was deleted.
26 package Int_IO is new Integer_IO(Small_Int); use Int_IO;
-- default format used at instantiation,
-- Default_Width = 4, Default_Base = 10
27 Put(126); -- "b126"
Put(-126, 7); -- "bbb-126"
Put(126, Width => 13, Base => 2); -- "bbb2#1111110#"
A.10.9 Input-Output for Real Types
Static Semantics
1 The following procedures are defined in the generic packages Float_IO,
Fixed_IO, and Decimal_IO, which have to be instantiated for the appropriate
floating point, ordinary fixed point, or decimal fixed point type respectively
(indicated by Num in the specifications).
2 Values are output as decimal literals without low line characters. The
format of each value output consists of a Fore field, a decimal point, an Aft
field, and (if a nonzero Exp parameter is supplied) the letter E and an Exp
field. The two possible formats thus correspond to:
3 Fore . Aft
4 and to:
5 Fore . Aft E Exp
6 without any spaces between these fields. The Fore field may include
leading spaces, and a minus sign for negative values. The Aft field includes
only decimal digits (possibly with trailing zeros). The Exp field includes the
sign (plus or minus) and the exponent (possibly with leading zeros).
7 For floating point types, the default lengths of these fields are defined
by the following variables that are declared in the generic package Float_IO:
8 Default_Fore : Field := 2;
Default_Aft : Field := Num'Digits-1;
Default_Exp : Field := 3;
9 For ordinary or decimal fixed point types, the default lengths of these
fields are defined by the following variables that are declared in the generic
packages Fixed_IO and Decimal_IO, respectively:
10 Default_Fore : Field := Num'Fore;
Default_Aft : Field := Num'Aft;
Default_Exp : Field := 0;
11 The following procedures are provided:
12 procedure Get(File : in File_Type; Item : out Num; Width : in Field := 0);
procedure Get(Item : out Num; Width : in Field := 0);
13 If the value of the parameter Width is zero, skips any leading
blanks, line terminators, or page terminators, then reads the
longest possible sequence of characters matching the syntax of any
of the following (see 2.4):
14 * [+|-]numeric_literal
15 * [+|-]numeral.[exponent]
16 * [+|-].numeral[exponent]
17 * [+|-]base#based_numeral.#[exponent]
18 * [+|-]base#.based_numeral#[exponent]
19 If a nonzero value of Width is supplied, then exactly Width
characters are input, or the characters (possibly none) up to a
line terminator, whichever comes first; any skipped leading blanks
are included in the count.
20 Returns in the parameter Item the value of type Num that
corresponds to the sequence input, preserving the sign (positive
if none has been specified) of a zero value if Num is a floating
point type and Num'Signed_Zeros is True.
21 The exception Data_Error is propagated if the sequence input does
not have the required syntax or if the value obtained is not of
the subtype Num.
22 procedure Put(File : in File_Type;
Item : in Num;
Fore : in Field := Default_Fore;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
procedure Put(Item : in Num;
Fore : in Field := Default_Fore;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
23 Outputs the value of the parameter Item as a decimal literal with
the format defined by Fore, Aft and Exp. If the value is negative,
or if Num is a floating point type where Num'Signed_Zeros is True
and the value is a negatively signed zero, then a minus sign is
included in the integer part. If Exp has the value zero, then the
integer part to be output has as many digits as are needed to
represent the integer part of the value of Item, overriding Fore
if necessary, or consists of the digit zero if the value of Item
has no integer part.
24 If Exp has a value greater than zero, then the integer part to be
output has a single digit, which is nonzero except for the value
0.0 of Item.
25 In both cases, however, if the integer part to be output has fewer
than Fore characters, including any minus sign, then leading
spaces are first output to make up the difference. The number of
digits of the fractional part is given by Aft, or is one if Aft
equals zero. The value is rounded; a value of exactly one half in
the last place is rounded away from zero.
26 If Exp has the value zero, there is no exponent part. If Exp has a
value greater than zero, then the exponent part to be output has
as many digits as are needed to represent the exponent part of the
value of Item (for which a single digit integer part is used), and
includes an initial sign (plus or minus). If the exponent part to
be output has fewer than Exp characters, including the sign, then
leading zeros precede the digits, to make up the difference. For
the value 0.0 of Item, the exponent has the value zero.
27 procedure Get(From : in String; Item : out Num; Last : out Positive);
28 Reads a real value from the beginning of the given string,
following the same rule as the Get procedure that reads a real
value from a file, but treating the end of the string as a file
terminator. Returns, in the parameter Item, the value of type Num
that corresponds to the sequence input. Returns in Last the index
value such that From(Last) is the last character read.
29 The exception Data_Error is propagated if the sequence input does
not have the required syntax, or if the value obtained is not of
the subtype Num.
30 procedure Put(To : out String;
Item : in Num;
Aft : in Field := Default_Aft;
Exp : in Field := Default_Exp);
31 Outputs the value of the parameter Item to the given string,
following the same rule as for output to a file, using a value for
Fore such that the sequence of characters output exactly fills the
string, including any leading spaces.
32 Float_Text_IO is a library package that is a nongeneric equivalent to
Text_IO.Float_IO for the predefined type Float:
33 with Ada.Text_IO;
package Ada.Float_Text_IO is new Ada.Text_IO.Float_IO(Float);
34 For each predefined floating point type, a nongeneric equivalent to
Text_IO.Float_IO is provided, with names such as Ada.Long_Float_Text_IO.
Implementation Permissions
35 An implementation may extend Get [and Put] for floating point types to
support special values such as infinities and NaNs.
35.a Discussion: See also the similar permission for the Wide_Value
attribute in 3.5.
36 The implementation of Put need not produce an output value with greater
accuracy than is supported for the base subtype. The additional accuracy, if
any, of the value produced by Put when the number of requested digits in the
integer and fractional parts exceeds the required accuracy is implementation
defined.
36.a Discussion: The required accuracy is thus Num'Base'Digits digits
if Num is a floating point subtype. For a fixed point subtype the
required accuracy is a function of the subtype's Fore, Aft, and
Delta attributes.
36.b Implementation defined: The accuracy of the value produced by Put.
37 The nongeneric equivalent packages may, but need not, be actual
instantiations of the generic package for the appropriate predefined type.
NOTES
38 30 For an item with a positive value, if output to a string exactly
fills the string without leading spaces, then output of the
corresponding negative value will propagate Layout_Error.
39 31 The rules for the Value attribute (see 3.5) and the rules for Get
are based on the same set of formats.
Examples
40/1 This paragraph was deleted.
41 package Real_IO is new Float_IO(Real); use Real_IO;
-- default format used at instantiation, Default_Exp = 3
42 X : Real := -123.4567; -- digits 8 (see 3.5.7)
43 Put(X); -- default format "-
1.2345670E+02"
Put(X, Fore => 5, Aft => 3, Exp => 2); -- "bbb-
1.235E+2"
Put(X, 5, 3, 0); -- "b-
123.457"
A.10.10 Input-Output for Enumeration Types
Static Semantics
1 The following procedures are defined in the generic package
Enumeration_IO, which has to be instantiated for the appropriate enumeration
type (indicated by Enum in the specification).
2 Values are output using either upper or lower case letters for
identifiers. This is specified by the parameter Set, which is of the
enumeration type Type_Set.
3 type Type_Set is (Lower_Case, Upper_Case);
4 The format (which includes any trailing spaces) can be specified by an
optional field width parameter. The default field width and letter case are
defined by the following variables that are declared in the generic package
Enumeration_IO:
5 Default_Width : Field := 0;
Default_Setting : Type_Set := Upper_Case;
6 The following procedures are provided:
7 procedure Get(File : in File_Type; Item : out Enum);
procedure Get(Item : out Enum);
8 After skipping any leading blanks, line terminators, or page
terminators, reads an identifier according to the syntax of this
lexical element (lower and upper case being considered
equivalent), or a character literal according to the syntax of
this lexical element (including the apostrophes). Returns, in the
parameter Item, the value of type Enum that corresponds to the
sequence input.
9 The exception Data_Error is propagated if the sequence input does
not have the required syntax, or if the identifier or character
literal does not correspond to a value of the subtype Enum.
10 procedure Put(File : in File_Type;
Item : in Enum;
Width : in Field := Default_Width;
Set : in Type_Set := Default_Setting);
procedure Put(Item : in Enum;
Width : in Field := Default_Width;
Set : in Type_Set := Default_Setting);
11 Outputs the value of the parameter Item as an enumeration literal
(either an identifier or a character literal). The optional
parameter Set indicates whether lower case or upper case is used
for identifiers; it has no effect for character literals. If the
sequence of characters produced has fewer than Width characters,
then trailing spaces are finally output to make up the difference.
If Enum is a character type, the sequence of characters produced
is as for Enum'Image(Item), as modified by the Width and Set
parameters.
11.a Discussion: For a character type, the literal might be a
Wide_Character or a control character. Whatever Image does for
these things is appropriate here, too.
12 procedure Get(From : in String; Item : out Enum; Last : out Positive);
13 Reads an enumeration value from the beginning of the given string,
following the same rule as the Get procedure that reads an
enumeration value from a file, but treating the end of the string
as a file terminator. Returns, in the parameter Item, the value of
type Enum that corresponds to the sequence input. Returns in Last
the index value such that From(Last) is the last character read.
14 The exception Data_Error is propagated if the sequence input does
not have the required syntax, or if the identifier or character
literal does not correspond to a value of the subtype Enum.
14.a To be honest: For a character type, it is permissible for the
implementation to make Get do the inverse of what Put does, in the
case of wide character_literals and control characters.
15 procedure Put(To : out String;
Item : in Enum;
Set : in Type_Set := Default_Setting);
16 Outputs the value of the parameter Item to the given string,
following the same rule as for output to a file, using the length
of the given string as the value for Width.
17/1 {8652/0054} {AI95-00007-01} Although the specification of the generic
package Enumeration_IO would allow instantiation for an integer type, this is
not the intended purpose of this generic package, and the effect of such
instantiations is not defined by the language.
NOTES
18 32 There is a difference between Put defined for characters, and for
enumeration values. Thus
19 Ada.Text_IO.Put('A'); -- outputs the character A
20 package Char_IO is new Ada.Text_IO.Enumeration_IO(Character);
Char_IO.Put('A'); -- outputs the character 'A', between apostrophes
21 33 The type Boolean is an enumeration type, hence Enumeration_IO can
be instantiated for this type.
Wording Changes from Ada 95
21.a/2 {8652/0054} {AI95-00007-01} Corrigendum: Corrected the wording to
say Enumeration_IO can be instantiated with an integer type, not a
float type.
A.10.11 Input-Output for Bounded Strings
1/2 {AI95-00428-01} The package Text_IO.Bounded_IO provides input-output in
human-readable form for Bounded_Strings.
Static Semantics
2/2 {AI95-00428-01} The generic library package Text_IO.Bounded_IO has the
following declaration:
3/2 with Ada.Strings.Bounded;
generic
with package Bounded is
new Ada.Strings.Bounded.Generic_Bounded_Length (<>);
package Ada.Text_IO.Bounded_IO is
4/2 procedure Put
(File : in File_Type;
Item : in Bounded.Bounded_String);
5/2 procedure Put
(Item : in Bounded.Bounded_String);
6/2 procedure Put_Line
(File : in File_Type;
Item : in Bounded.Bounded_String);
7/2 procedure Put_Line
(Item : in Bounded.Bounded_String);
8/2 function Get_Line
(File : in File_Type)
return Bounded.Bounded_String;
9/2 function Get_Line
return Bounded.Bounded_String;
10/2 procedure Get_Line
(File : in File_Type; Item : out Bounded.Bounded_String);
11/2 procedure Get_Line
(Item : out Bounded.Bounded_String);
12/2 end Ada.Text_IO.Bounded_IO;
13/2 {AI95-00428-01} For an item of type Bounded_String, the following
subprograms are provided:
14/2 procedure Put
(File : in File_Type;
Item : in Bounded.Bounded_String);
15/2 {AI95-00428-01} Equivalent to Text_IO.Put (File,
Bounded.To_String(Item));
16/2 procedure Put
(Item : in Bounded.Bounded_String);
17/2 {AI95-00428-01} Equivalent to Text_IO.Put
(Bounded.To_String(Item));
18/2 procedure Put_Line
(File : in File_Type;
Item : in Bounded.Bounded_String);
19/2 {AI95-00428-01} Equivalent to Text_IO.Put_Line (File,
Bounded.To_String(Item));
20/2 procedure Put_Line
(Item : in Bounded.Bounded_String);
21/2 {AI95-00428-01} Equivalent to Text_IO.Put_Line
(Bounded.To_String(Item));
22/2 function Get_Line
(File : in File_Type)
return Bounded.Bounded_String;
23/2 {AI95-00428-01} Returns
Bounded.To_Bounded_String(Text_IO.Get_Line(File));
24/2 function Get_Line
return Bounded.Bounded_String;
25/2 {AI95-00428-01} Returns
Bounded.To_Bounded_String(Text_IO.Get_Line);
26/2 procedure Get_Line
(File : in File_Type; Item : out Bounded.Bounded_String);
27/2 {AI95-00428-01} Equivalent to Item := Get_Line (File);
28/2 procedure Get_Line
(Item : out Bounded.Bounded_String);
29/2 {AI95-00428-01} Equivalent to Item := Get_Line;
Extensions to Ada 95
29.a/2 {AI95-00428-01} {extensions to Ada 95} Package Text_IO.Bounded_IO
is new.
A.10.12 Input-Output for Unbounded Strings
1/2 {AI95-00301-01} The package Text_IO.Unbounded_IO provides input-output in
human-readable form for Unbounded_Strings.
Static Semantics
2/2 {AI95-00301-01} The library package Text_IO.Unbounded_IO has the following
declaration:
3/2 with Ada.Strings.Unbounded;
package Ada.Text_IO.Unbounded_IO is
4/2 procedure Put
(File : in File_Type;
Item : in Strings.Unbounded.Unbounded_String);
5/2 procedure Put
(Item : in Strings.Unbounded.Unbounded_String);
6/2 procedure Put_Line
(File : in File_Type;
Item : in Strings.Unbounded.Unbounded_String);
7/2 procedure Put_Line
(Item : in Strings.Unbounded.Unbounded_String);
8/2 function Get_Line
(File : in File_Type)
return Strings.Unbounded.Unbounded_String;
9/2 function Get_Line
return Strings.Unbounded.Unbounded_String;
10/2 procedure Get_Line
(File : in File_Type; Item : out Strings.Unbounded.Unbounded_String);
11/2 procedure Get_Line
(Item : out Strings.Unbounded.Unbounded_String);
12/2 end Ada.Text_IO.Unbounded_IO;
13/2 {AI95-00301-01} For an item of type Unbounded_String, the following
subprograms are provided:
14/2 procedure Put
(File : in File_Type;
Item : in Strings.Unbounded.Unbounded_String);
15/2 {AI95-00301-01} Equivalent to Text_IO.Put (File,
Strings.Unbounded.To_String(Item));
16/2 procedure Put
(Item : in Strings.Unbounded.Unbounded_String);
17/2 {AI95-00301-01} Equivalent to Text_IO.Put
(Strings.Unbounded.To_String(Item));
18/2 procedure Put_Line
(File : in File_Type;
Item : in Strings.Unbounded.Unbounded_String);
19/2 {AI95-00301-01} Equivalent to Text_IO.Put_Line (File,
Strings.Unbounded.To_String(Item));
20/2 procedure Put_Line
(Item : in Strings.Unbounded.Unbounded_String);
21/2 {AI95-00301-01} Equivalent to Text_IO.Put_Line
(Strings.Unbounded.To_String(Item));
22/2 function Get_Line
(File : in File_Type)
return Strings.Unbounded.Unbounded_String;
23/2 {AI95-00301-01} Returns
Strings.Unbounded.To_Unbounded_String(Text_IO.Get_Line(File));
24/2 function Get_Line
return Strings.Unbounded.Unbounded_String;
25/2 {AI95-00301-01} Returns
Strings.Unbounded.To_Unbounded_String(Text_IO.Get_Line);
26/2 procedure Get_Line
(File : in File_Type; Item : out Strings.Unbounded.Unbounded_String);
27/2 {AI95-00301-01} Equivalent to Item := Get_Line (File);
28/2 procedure Get_Line
(Item : out Strings.Unbounded.Unbounded_String);
29/2 {AI95-00301-01} Equivalent to Item := Get_Line;
Extensions to Ada 95
29.a/2 {AI95-00301-01} {extensions to Ada 95} Package
Text_IO.Unbounded_IO is new.
A.11 Wide Text Input-Output and Wide Wide Text Input-Output
1/2 {AI95-00285-01} The packages Wide_Text_IO and Wide_Wide_Text_IO provide
facilities for input and output in human-readable form. Each file is read or
written sequentially, as a sequence of wide characters (or wide wide
characters) grouped into lines, and as a sequence of lines grouped into pages.
Static Semantics
2/2 {AI95-00285-01} {AI95-00301-01} The specification of package Wide_Text_IO
is the same as that for Text_IO, except that in each Get, Look_Ahead,
Get_Immediate, Get_Line, Put, and Put_Line subprogram, any occurrence of
Character is replaced by Wide_Character, and any occurrence of String is
replaced by Wide_String. Nongeneric equivalents of Wide_Text_IO.Integer_IO and
Wide_Text_IO.Float_IO are provided (as for Text_IO) for each predefined
numeric type, with names such as Ada.Integer_Wide_Text_IO, Ada.Long_Integer_-
Wide_Text_IO, Ada.Float_Wide_Text_IO, Ada.Long_Float_Wide_Text_IO.
3/2 {AI95-00285-01} {AI95-00301-01} The specification of package
Wide_Wide_Text_IO is the same as that for Text_IO, except that in each Get,
Look_Ahead, Get_Immediate, Get_Line, Put, and Put_Line subprogram, any
occurrence of Character is replaced by Wide_Wide_Character, and any occurrence
of String is replaced by Wide_Wide_String. Nongeneric equivalents of
Wide_Wide_Text_IO.Integer_IO and Wide_Wide_Text_IO.Float_IO are provided (as
for Text_IO) for each predefined numeric type, with names such as Ada.Integer_-
Wide_Wide_Text_IO, Ada.Long_Integer_Wide_Wide_Text_IO, Ada.Float_Wide_Wide_-
Text_IO, Ada.Long_Float_Wide_Wide_Text_IO.
4/2 {AI95-00285-01} {AI95-00428-01} The specification of package
Wide_Text_IO.Wide_Bounded_IO is the same as that for Text_IO.Bounded_IO,
except that any occurrence of Bounded_String is replaced by Wide_Bounded_-
String, and any occurrence of package Bounded is replaced by Wide_Bounded. The
specification of package Wide_Wide_Text_IO.Wide_Wide_Bounded_IO is the same as
that for Text_IO.Bounded_IO, except that any occurrence of Bounded_String is
replaced by Wide_Wide_Bounded_String, and any occurrence of package Bounded is
replaced by Wide_Wide_Bounded.
5/2 {AI95-00285-01} {AI95-00301-01} The specification of package Wide_Text_IO.-
Wide_Unbounded_IO is the same as that for Text_IO.Unbounded_IO, except that
any occurrence of Unbounded_String is replaced by Wide_Unbounded_String, and
any occurrence of package Unbounded is replaced by Wide_Unbounded. The
specification of package Wide_Wide_Text_IO.Wide_Wide_Unbounded_IO is the same
as that for Text_IO.Unbounded_IO, except that any occurrence of
Unbounded_String is replaced by Wide_Wide_Unbounded_String, and any occurrence
of package Unbounded is replaced by Wide_Wide_Unbounded.
Extensions to Ada 83
5.a {extensions to Ada 83} Support for Wide_Character and Wide_String
I/O is new in Ada 95.
Extensions to Ada 95
5.b/2 {AI95-00285-01} {extensions to Ada 95} Package Wide_Wide_Text_IO
is new. Be glad it wasn't called Double_Wide_Text_IO (for use in
trailer parks) or Really_Wide_Text_IO.
5.c/2 {AI95-00301-01} Packages Wide_Text_IO.Wide_Unbounded_IO and
Wide_Wide_Text_IO.Wide_Wide_Unbounded_IO are also new.
5.d/2 {AI95-00428-01} Packages Wide_Text_IO.Wide_Bounded_IO and
Wide_Wide_Text_IO.Wide_Wide_Bounded_IO are new as well.
A.12 Stream Input-Output
1/2 {AI95-00285-01} The packages Streams.Stream_IO, Text_IO.Text_Streams,
Wide_Text_IO.Text_Streams, and Wide_Wide_Text_IO.Text_Streams provide
stream-oriented operations on files.
Wording Changes from Ada 95
1.a/2 {AI95-00285-01} Included package Wide_Wide_Text_IO.Text_Streams in
this description.
A.12.1 The Package Streams.Stream_IO
1 {heterogeneous input-output} [The subprograms in the child package
Streams.Stream_IO provide control over stream files. Access to a stream file
is either sequential, via a call on Read or Write to transfer an array of
stream elements, or positional (if supported by the implementation for the
given file), by specifying a relative index for an element. Since a stream
file can be converted to a Stream_Access value, calling stream-oriented
attribute subprograms of different element types with the same Stream_Access
value provides heterogeneous input-output.] See 13.13 for a general discussion
of streams.
Static Semantics
1.1/1 {8652/0055} {AI95-00026-01} The elements of a stream file are stream
elements. If positioning is supported for the specified external file, a
current index and current size are maintained for the file as described in
A.8. If positioning is not supported, a current index is not maintained, and
the current size is implementation
defined.{Current index (of an open stream file)} {Current size (of a stream file)}
1.a.1/1 Implementation defined: Current size for a stream file for which
positioning is not supported.
2 The library package Streams.Stream_IO has the following declaration:
3 with Ada.IO_Exceptions;
package Ada.Streams.Stream_IO is
4 type Stream_Access is access all Root_Stream_Type'Class;
5 type File_Type is limited private;
6 type File_Mode is (In_File, Out_File, Append_File);
7 type Count is range 0 .. implementation-defined;
subtype Positive_Count is Count range 1 .. Count'Last;
-- Index into file, in stream elements.
8 procedure Create (File : in out File_Type;
Mode : in File_Mode := Out_File;
Name : in String := "";
Form : in String := "");
9 procedure Open (File : in out File_Type;
Mode : in File_Mode;
Name : in String;
Form : in String := "");
10 procedure Close (File : in out File_Type);
procedure Delete (File : in out File_Type);
procedure Reset (File : in out File_Type; Mode : in File_Mode);
procedure Reset (File : in out File_Type);
11 function Mode (File : in File_Type) return File_Mode;
function Name (File : in File_Type) return String;
function Form (File : in File_Type) return String;
12 function Is_Open (File : in File_Type) return Boolean;
function End_Of_File (File : in File_Type) return Boolean;
13 function Stream (File : in File_Type) return Stream_Access;
-- Return stream access for use with T'Input and T'Output
14/1 This paragraph was deleted.
15 -- Read array of stream elements from file
procedure Read (File : in File_Type;
Item : out Stream_Element_Array;
Last : out Stream_Element_Offset;
From : in Positive_Count);
16 procedure Read (File : in File_Type;
Item : out Stream_Element_Array;
Last : out Stream_Element_Offset);
17/1 This paragraph was deleted.
18 -- Write array of stream elements into file
procedure Write (File : in File_Type;
Item : in Stream_Element_Array;
To : in Positive_Count);
19 procedure Write (File : in File_Type;
Item : in Stream_Element_Array);
20/1 This paragraph was deleted.
21 -- Operations on position within file
22 procedure Set_Index(File : in File_Type; To : in Positive_Count);
23 function Index(File : in File_Type) return Positive_Count;
function Size (File : in File_Type) return Count;
24 procedure Set_Mode(File : in out File_Type; Mode : in File_Mode);
25/1 {8652/0051} {AI95-00057-01} procedure Flush(File : in File_Type);
26 -- exceptions
Status_Error : exception renames IO_Exceptions.Status_Error;
Mode_Error : exception renames IO_Exceptions.Mode_Error;
Name_Error : exception renames IO_Exceptions.Name_Error;
Use_Error : exception renames IO_Exceptions.Use_Error;
Device_Error : exception renames IO_Exceptions.Device_Error;
End_Error : exception renames IO_Exceptions.End_Error;
Data_Error : exception renames IO_Exceptions.Data_Error;
27 private
... -- not specified by the language
end Ada.Streams.Stream_IO;
27.1/2 {AI95-00360-01} The type File_Type needs finalization (see 7.6).
28/2 {AI95-00283-01} The subprograms given in subclause A.8.2 for the control
of external files (Create, Open, Close, Delete, Reset, Mode, Name, Form, and
Is_Open) are available for stream files.
28.1/2 {AI95-00283-01} The End_Of_File function:
28.2/2 * Propagates Mode_Error if the mode of the file is not In_File;
28.3/2 * If positioning is supported for the given external file, the
function returns True if the current index exceeds the size of the
external file; otherwise it returns False;
28.4/2 * If positioning is not supported for the given external file, the
function returns True if no more elements can be read from the given
file; otherwise it returns False.
28.5/2 {8652/0055} {AI95-00026-01} {AI95-00085-01} The Set_Mode procedure sets
the mode of the file. If the new mode is Append_File, the file is positioned
to its end; otherwise, the position in the file is unchanged.
28.6/1 {8652/0055} {AI95-00026-01} The Flush procedure synchronizes the
external file with the internal file (by flushing any internal buffers)
without closing the file or changing the position. Mode_Error is propagated if
the mode of the file is In_File.
29/1 {8652/0056} {AI95-00001-01} The Stream function returns a Stream_Access
result from a File_Type object, thus allowing the stream-oriented attributes
Read, Write, Input, and Output to be used on the same file for multiple types.
Stream propagates Status_Error if File is not open.
30/2 {AI95-00256-01} The procedures Read and Write are equivalent to the
corresponding operations in the package Streams. Read propagates Mode_Error if
the mode of File is not In_File. Write propagates Mode_Error if the mode of
File is not Out_File or Append_File. The Read procedure with a Positive_Count
parameter starts reading at the specified index. The Write procedure with a
Positive_Count parameter starts writing at the specified index. For a file
that supports positioning, Read without a Positive_Count parameter starts
reading at the current index, and Write without a Positive_Count parameter
starts writing at the current index.
30.1/1 {8652/0055} {AI95-00026-01} The Size function returns the current size
of the file.
31/1 {8652/0055} {AI95-00026-01} The Index function returns the current index.
31.a/1 This paragraph was deleted.
32 The Set_Index procedure sets the current index to the specified value.
32.1/1 {8652/0055} {AI95-00026-01} If positioning is supported for the
external file, the current index is maintained as follows:
32.2/1 * {8652/0055} {AI95-00026-01} For Open and Create, if the Mode
parameter is Append_File, the current index is set to the current size
of the file plus one; otherwise, the current index is set to one.
32.3/1 * {8652/0055} {AI95-00026-01} For Reset, if the Mode parameter is
Append_File, or no Mode parameter is given and the current mode is
Append_File, the current index is set to the current size of the file
plus one; otherwise, the current index is set to one.
32.4/1 * {8652/0055} {AI95-00026-01} For Set_Mode, if the new mode is
Append_File, the current index is set to current size plus one;
otherwise, the current index is unchanged.
32.5/1 * {8652/0055} {AI95-00026-01} For Read and Write without a
Positive_Count parameter, the current index is incremented by the
number of stream elements read or written.
32.6/1 * {8652/0055} {AI95-00026-01} For Read and Write with a
Positive_Count parameter, the value of the current index is set to the
value of the Positive_Count parameter plus the number of stream
elements read or written.
33 If positioning is not supported for the given file, then a call of Index
or Set_Index propagates Use_Error. Similarly, a call of Read or Write with a
Positive_Count parameter propagates Use_Error.
33.a/2 Implementation Note: {AI95-00085-01} It is permissible for an
implementation to implement mode Append_File using the Unix append
mode (the O_APPEND bit). Such an implementation does not support
positioning when the mode is Append_File, and therefore the
operations listed above must raise Use_Error. This is acceptable
as there is no requirement that any particular file support
positioning; therefore it is acceptable that a file support
positioning when opened with mode Out_File, and the same file not
support positioning when opened with mode Append_File. But it is
not acceptable for a file to support positioning (by allowing the
above operations), but to do something other than the defined
semantics (that is, always write at the end, even when explicitly
commanded to write somewhere else).
Paragraphs 34 through 36 were deleted.
Erroneous Execution
36.1/1 {8652/0056} {AI95-00001-01} {erroneous execution (cause) [partial]} If
the File_Type object passed to the Stream function is later closed or
finalized, and the stream-oriented attributes are subsequently called
(explicitly or implicitly) on the Stream_Access value returned by Stream,
execution is erroneous. This rule applies even if the File_Type object was
opened again after it had been closed.
36.a.1/1 Reason: These rules are analogous to the rule for the result of
the Current_Input, Current_Output, and Current_Error functions.
These rules make it possible to represent a value of (some
descendant of) Root_Stream_Type which represents a file as an
access value, with a null value corresponding to a closed file.
Inconsistencies With Ada 95
36.a/2 {AI95-00283-01} {inconsistencies with Ada 95} Amendment
Correction: The description of the subprograms for managing files
was corrected so that they do not require truncation of the
external file - a stream file is not a sequential file. An Ada 95
program that expects truncation of the stream file may not work
under Ada 2005. Note that the Ada 95 standard was ambiguous on
this point (the normative wording seemed to require truncation,
but didn't explain where; the AARM notes seemed to expect behavior
like Direct_IO), and implementations varied widely. Therefore, as
a practical matter, code that depends on stream truncation may not
work even in Ada 95; deleting the file before opening it provides
truncation that works in both Ada 95 and Ada 2005.
Incompatibilities With Ada 95
36.b/2 {AI95-00360-01} {incompatibilities with Ada 95} Amendment
Correction: Stream_IO.File_Type is defined to need finalization.
If the restriction No_Nested_Finalization (see D.7) applies to the
partition, and File_Type does not have a controlled part, it will
not be allowed in local objects in Ada 2005 whereas it would be
allowed in original Ada 95. Such code is not portable, as another
Ada compiler may have a controlled part in File_Type, and thus
would be illegal.
Wording Changes from Ada 95
36.c/2 {8652/0051} {AI95-00057-01} Corrigendum: Corrected the parameter
mode of Flush; otherwise it could not be used on Standard_Output.
36.d/2 {8652/0055} {AI95-00026-01} {AI95-00256-01} Corrigendum: Added
wording to describe the effects of the various operations on the
current index. The Amendment adds an explanation of the use of
current index for Read and Write.
36.e/2 {8652/0056} {AI95-00001-01} Corrigendum: Clarified that Stream can
raise Status_Error, and clarified that using a Stream_Access whose
file has been closed is erroneous.
36.f/2 {AI95-00085-01} Clarified that Set_Mode can be called with the
current mode.
A.12.2 The Package Text_IO.Text_Streams
1 The package Text_IO.Text_Streams provides a function for treating a text
file as a stream.
Static Semantics
2 The library package Text_IO.Text_Streams has the following declaration:
3 with Ada.Streams;
package Ada.Text_IO.Text_Streams is
type Stream_Access is access all Streams.Root_Stream_Type'Class;
4 function Stream (File : in File_Type) return Stream_Access;
end Ada.Text_IO.Text_Streams;
5 The Stream function has the same effect as the corresponding function in
Streams.Stream_IO.
NOTES
6 34 The ability to obtain a stream for a text file allows
Current_Input, Current_Output, and Current_Error to be processed with
the functionality of streams, including the mixing of text and binary
input-output, and the mixing of binary input-output for different
types.
7 35 Performing operations on the stream associated with a text file
does not affect the column, line, or page counts.
A.12.3 The Package Wide_Text_IO.Text_Streams
1 The package Wide_Text_IO.Text_Streams provides a function for treating a
wide text file as a stream.
Static Semantics
2 The library package Wide_Text_IO.Text_Streams has the following
declaration:
3 with Ada.Streams;
package Ada.Wide_Text_IO.Text_Streams is
type Stream_Access is access all Streams.Root_Stream_Type'Class;
4 function Stream (File : in File_Type) return Stream_Access;
end Ada.Wide_Text_IO.Text_Streams;
5 The Stream function has the same effect as the corresponding function in
Streams.Stream_IO.
A.12.4 The Package Wide_Wide_Text_IO.Text_Streams
1/2 {AI95-00285-01} The package Wide_Wide_Text_IO.Text_Streams provides a
function for treating a wide wide text file as a stream.
Static Semantics
2/2 {AI95-00285-01} The library package Wide_Wide_Text_IO.Text_Streams has the
following declaration:
3/2 with Ada.Streams;
package Ada.Wide_Wide_Text_IO.Text_Streams is
type Stream_Access is access all Streams.Root_Stream_Type'Class;
4/2 function Stream (File : in File_Type) return Stream_Access;
end Ada.Wide_Wide_Text_IO.Text_Streams;
5/2 {AI95-00285-01} The Stream function has the same effect as the
corresponding function in Streams.Stream_IO.
Extensions to Ada 95
5.a/2 {AI95-00285-01} {extensions to Ada 95} Package
Wide_Wide_Text_IO.Text_Streams is new.
A.13 Exceptions in Input-Output
1 The package IO_Exceptions defines the exceptions needed by the predefined
input-output packages.
Static Semantics
2 The library package IO_Exceptions has the following declaration:
3 package Ada.IO_Exceptions is
pragma Pure(IO_Exceptions);
4 Status_Error : exception;
Mode_Error : exception;
Name_Error : exception;
Use_Error : exception;
Device_Error : exception;
End_Error : exception;
Data_Error : exception;
Layout_Error : exception;
5 end Ada.IO_Exceptions;
6 If more than one error condition exists, the corresponding exception that
appears earliest in the following list is the one that is propagated.
7 The exception Status_Error is propagated by an attempt to operate upon a
file that is not open, and by an attempt to open a file that is already open.
8 The exception Mode_Error is propagated by an attempt to read from, or test
for the end of, a file whose current mode is Out_File or Append_File, and also
by an attempt to write to a file whose current mode is In_File. In the case of
Text_IO, the exception Mode_Error is also propagated by specifying a file
whose current mode is Out_File or Append_File in a call of Set_Input,
Skip_Line, End_Of_Line, Skip_Page, or End_Of_Page; and by specifying a file
whose current mode is In_File in a call of Set_Output, Set_Line_Length,
Set_Page_Length, Line_Length, Page_Length, New_Line, or New_Page.
9 The exception Name_Error is propagated by a call of Create or Open if the
string given for the parameter Name does not allow the identification of an
external file. For example, this exception is propagated if the string is
improper, or, alternatively, if either none or more than one external file
corresponds to the string.
10 The exception Use_Error is propagated if an operation is attempted that is
not possible for reasons that depend on characteristics of the external file.
For example, this exception is propagated by the procedure Create, among other
circumstances, if the given mode is Out_File but the form specifies an input
only device, if the parameter Form specifies invalid access rights, or if an
external file with the given name already exists and overwriting is not
allowed.
11 The exception Device_Error is propagated if an input-output operation
cannot be completed because of a malfunction of the underlying system.
12 The exception End_Error is propagated by an attempt to skip (read past)
the end of a file.
13 The exception Data_Error can be propagated by the procedure Read (or by
the Read attribute) if the element read cannot be interpreted as a value of
the required subtype. This exception is also propagated by a procedure Get
(defined in the package Text_IO) if the input character sequence fails to
satisfy the required syntax, or if the value input does not belong to the
range of the required subtype.
14 The exception Layout_Error is propagated (in text input-output) by Col,
Line, or Page if the value returned exceeds Count'Last. The exception
Layout_Error is also propagated on output by an attempt to set column or line
numbers in excess of specified maximum line or page lengths, respectively
(excluding the unbounded cases). It is also propagated by an attempt to Put
too many characters to a string.
Documentation Requirements
15 The implementation shall document the conditions under which Name_Error,
Use_Error and Device_Error are propagated.
15.a/2 Documentation Requirement: The conditions under which
Io_Exceptions.Name_Error, Io_Exceptions.Use_Error, and
Io_Exceptions.Device_Error are propagated.
Implementation Permissions
16 If the associated check is too complex, an implementation need not
propagate Data_Error as part of a procedure Read (or the Read attribute) if
the value read cannot be interpreted as a value of the required subtype.
16.a Ramification: An example where the implementation may choose not
to perform the check is an enumeration type with a representation
clause with "holes" in the range of internal codes.
Erroneous Execution
17 {erroneous execution (cause) [partial]} [If the element read by the
procedure Read (or by the Read attribute) cannot be interpreted as a value of
the required subtype, but this is not detected and Data_Error is not
propagated, then the resulting value can be abnormal, and subsequent
references to the value can lead to erroneous execution, as explained in
13.9.1. {normal state of an object [partial]} {abnormal state of an object
[partial]} ]
A.14 File Sharing
Dynamic Semantics
1 {unspecified [partial]} It is not specified by the language whether the
same external file can be associated with more than one file object. If such
sharing is supported by the implementation, the following effects are defined:
2 * Operations on one text file object do not affect the column, line, and
page numbers of any other file object.
3/1 * This paragraph was deleted.{8652/0057} {AI95-00050-01}
4 * For direct and stream files, the current index is a property of each
file object; an operation on one file object does not affect the
current index of any other file object.
5 * For direct and stream files, the current size of the file is a
property of the external file.
6 All other effects are identical.
Wording Changes from Ada 95
6.a/2 {8652/0057} {AI95-00050-01} Corrigendum: Removed the incorrect
statement that the external files associated with the standard
input, standard output, and standard error files are distinct.
A.15 The Package Command_Line
1 The package Command_Line allows a program to obtain the values of its
arguments and to set the exit status code to be returned on normal
termination.
1.a/2 Implementation defined: The meaning of Argument_Count, Argument,
and Command_Name for package Command_Line. The bounds of type
Command_Line.Exit_Status.
Static Semantics
2 The library package Ada.Command_Line has the following declaration:
3 package Ada.Command_Line is
pragma Preelaborate(Command_Line);
4 function Argument_Count return Natural;
5 function Argument (Number : in Positive) return String;
6 function Command_Name return String;
7 type Exit_Status is implementation-defined integer type;
8 Success : constant Exit_Status;
Failure : constant Exit_Status;
9 procedure Set_Exit_Status (Code : in Exit_Status);
10 private
... -- not specified by the language
end Ada.Command_Line;
11 function Argument_Count return Natural;
12 If the external execution environment supports passing arguments
to a program, then Argument_Count returns the number of arguments
passed to the program invoking the function. Otherwise it returns
0. The meaning of "number of arguments" is implementation defined.
13 function Argument (Number : in Positive) return String;
14 If the external execution environment supports passing arguments
to a program, then Argument returns an implementation-defined
value corresponding to the argument at relative position Number.
{Constraint_Error (raised by failure of run-time check)} If Number
is outside the range 1..Argument_Count, then Constraint_Error is
propagated.
14.a Ramification: If the external execution environment does not
support passing arguments to a program, then Argument(N) for any N
will raise Constraint_Error, since Argument_Count is 0.
15 function Command_Name return String;
16 If the external execution environment supports passing arguments
to a program, then Command_Name returns an implementation-defined
value corresponding to the name of the command invoking the
program; otherwise Command_Name returns the null string.
16.1/1 type Exit_Status is implementation-defined integer type;
17 The type Exit_Status represents the range of exit status values
supported by the external execution environment. The constants
Success and Failure correspond to success and failure,
respectively.
18 procedure Set_Exit_Status (Code : in Exit_Status);
19 If the external execution environment supports returning an exit
status from a program, then Set_Exit_Status sets Code as the
status. Normal termination of a program returns as the exit status
the value most recently set by Set_Exit_Status, or, if no such
value has been set, then the value Success. If a program
terminates abnormally, the status set by Set_Exit_Status is
ignored, and an implementation-defined exit status value is set.
20 If the external execution environment does not support returning
an exit value from a program, then Set_Exit_Status does nothing.
Implementation Permissions
21 An alternative declaration is allowed for package Command_Line if
different functionality is appropriate for the external execution environment.
NOTES
22 36 Argument_Count, Argument, and Command_Name correspond to the C
language's argc, argv[n] (for n>0) and argv[0], respectively.
22.a To be honest: The correspondence of Argument_Count to argc is not
direct - argc would be one more than Argument_Count, since the
argc count includes the command name, whereas Argument_Count does
not.
Extensions to Ada 83
22.b {extensions to Ada 83} This clause is new in Ada 95.
A.16 The Package Directories
1/2 {AI95-00248-01} The package Directories provides operations for
manipulating files and directories, and their names.
1.a/2 Discussion: The notes for this clause contain the expected
interpretations of some of the operations on various target
systems. "Unix" refers to the UNIX® operating system, and in most
cases also covers Unix-like systems such as Linux and POSIX. "
Windows®" refers to the Microsoft® Windows® 2000 operating system
and usually also covers most other versions that use the Win32
API.
Static Semantics
2/2 {AI95-00248-01} The library package Directories has the following
declaration:
3/2 with Ada.IO_Exceptions;
with Ada.Calendar;
package Ada.Directories is
4/2 -- Directory and file operations:
5/2 function Current_Directory return String;
6/2 procedure Set_Directory (Directory : in String);
7/2 procedure Create_Directory (New_Directory : in String;
Form : in String := "");
8/2 procedure Delete_Directory (Directory : in String);
9/2 procedure Create_Path (New_Directory : in String;
Form : in String := "");
10/2 procedure Delete_Tree (Directory : in String);
11/2 procedure Delete_File (Name : in String);
12/2 procedure Rename (Old_Name, New_Name : in String);
13/2 procedure Copy_File (Source_Name,
Target_Name : in String;
Form : in String := "");
14/2 -- File and directory name operations:
15/2 function Full_Name (Name : in String) return String;
16/2 function Simple_Name (Name : in String) return String;
17/2 function Containing_Directory (Name : in String) return String;
18/2 function Extension (Name : in String) return String;
19/2 function Base_Name (Name : in String) return String;
20/2 function Compose (Containing_Directory : in String := "";
Name : in String;
Extension : in String := "") return String;
21/2 -- File and directory queries:
22/2 type File_Kind is (Directory, Ordinary_File, Special_File);
23/2 type File_Size is range 0 .. implementation-defined;
24/2 function Exists (Name : in String) return Boolean;
25/2 function Kind (Name : in String) return File_Kind;
26/2 function Size (Name : in String) return File_Size;
27/2 function Modification_Time
(Name : in String) return Ada.Calendar.Time;
28/2 -- Directory searching:
29/2 type Directory_Entry_Type is limited private;
30/2 type Filter_Type is array (File_Kind) of Boolean;
31/2 type Search_Type is limited private;
32/2 procedure Start_Search (Search : in out Search_Type;
Directory : in String;
Pattern : in String;
Filter : in Filter_Type := (others => True));
33/2 procedure End_Search (Search : in out Search_Type);
34/2 function More_Entries (Search : in Search_Type) return Boolean;
35/2 procedure Get_Next_Entry (Search : in out Search_Type;
Directory_Entry : out Directory_Entry_Type);
36/2 procedure Search (
Directory : in String;
Pattern : in String;
Filter : in Filter_Type := (others => True);
Process : not null access procedure (
Directory_Entry : in Directory_Entry_Type));
37/2 -- Operations on Directory Entries:
38/2 function Simple_Name (Directory_Entry : in Directory_Entry_Type)
return String;
39/2 function Full_Name (Directory_Entry : in Directory_Entry_Type)
return String;
40/2 function Kind (Directory_Entry : in Directory_Entry_Type)
return File_Kind;
41/2 function Size (Directory_Entry : in Directory_Entry_Type)
return File_Size;
42/2 function Modification_Time
(Directory_Entry : in Directory_Entry_Type)
return Ada.Calendar.Time;
43/2 Status_Error : exception renames Ada.IO_Exceptions.Status_Error;
Name_Error : exception renames Ada.IO_Exceptions.Name_Error;
Use_Error : exception renames Ada.IO_Exceptions.Use_Error;
Device_Error : exception renames Ada.IO_Exceptions.Device_Error;
44/2 private
-- Not specified by the language.
end Ada.Directories;
45/2 {AI95-00248-01} External files may be classified as directories, special
files, or ordinary files. A directory is an external file that is a container
for files on the target system. A special file is an external file that cannot
be created or read by a predefined Ada input-output package. External files
that are not special files or directories are called ordinary files.
{directory} {special file} {ordinary file}
45.a/2 Ramification: A directory is an external file, although it may not
have a name on some targets. A directory is not a special file, as
it can be created and read by Directories.
45.b/2 Discussion: Devices and soft links are examples of special files
on Windows® and Unix.
45.c/2 Even if an implementation provides a package to create and read
soft links, such links are still special files.
46/2 {AI95-00248-01} A file name is a string identifying an external file.
Similarly, a directory name is a string identifying a directory. The
interpretation of file names and directory names is implementation-defined.
{directory name} {file name}
46.a/2 Implementation defined: The interpretation of file names and
directory names.
47/2 {AI95-00248-01} The full name of an external file is a full specification
of the name of the file. If the external environment allows alternative
specifications of the name (for example, abbreviations), the full name should
not use such alternatives. A full name typically will include the names of all
of the directories that contain the item. The simple name of an external file
is the name of the item, not including any containing directory names. Unless
otherwise specified, a file name or directory name parameter in a call to a
predefined Ada input-output subprogram can be a full name, a simple name, or
any other form of name supported by the implementation.
{full name (of a file)} {simple name (of a file)}
47.a/2 Discussion: The full name on Unix is a complete path to the root.
For Windows®, the full name includes a complete path, as well as a
disk name ("C:") or network share name. For both systems, the
simple name is the part of the name following the last '/' (or '\'
for Windows®). For example, in the name
"/usr/randy/ada-directories.ads", "ada-directories.ads" is the
simple name.
47.b/2 Ramification: It is possible for a file or directory name to be
neither a full name nor a simple name. For instance, the Unix name
"../parent/myfile" is neither a full name nor a simple name.
48/2 {AI95-00248-01} The default directory is the directory that is used if a
directory or file name is not a full name (that is, when the name does not
fully identify all of the containing directories). {default directory}
48.a/2 Discussion: The default directory is the one maintained by the
familiar "cd" command on Unix and Windows®. Note that Windows®
maintains separate default directories for each disk drive;
implementations should use the natural implementation.
49/2 {AI95-00248-01} A directory entry is a single item in a directory,
identifying a single external file (including directories and special files).
{directory entry}
50/2 {AI95-00248-01} For each function that returns a string, the lower bound
of the returned value is 1.
51/2 {AI95-00248-01} The following file and directory operations are provided:
52/2 function Current_Directory return String;
53/2 Returns the full directory name for the current default directory.
The name returned shall be suitable for a future call to
Set_Directory. The exception Use_Error is propagated if a default
directory is not supported by the external environment.
54/2 procedure Set_Directory (Directory : in String);
55/2 Sets the current default directory. The exception Name_Error is
propagated if the string given as Directory does not identify an
existing directory. The exception Use_Error is propagated if the
external environment does not support making Directory (in the
absence of Name_Error) a default directory.
56/2 procedure Create_Directory (New_Directory : in String;
Form : in String := "");
57/2 Creates a directory with name New_Directory. The Form parameter
can be used to give system-dependent characteristics of the
directory; the interpretation of the Form parameter is
implementation-defined. A null string for Form specifies the use
of the default options of the implementation of the new directory.
The exception Name_Error is propagated if the string given as
New_Directory does not allow the identification of a directory.
The exception Use_Error is propagated if the external environment
does not support the creation of a directory with the given name
(in the absence of Name_Error) and form.
58/2 procedure Delete_Directory (Directory : in String);
59/2 Deletes an existing empty directory with name Directory. The
exception Name_Error is propagated if the string given as
Directory does not identify an existing directory. The exception
Use_Error is propagated if the external environment does not
support the deletion of the directory (or some portion of its
contents) with the given name (in the absence of Name_Error).
60/2 procedure Create_Path (New_Directory : in String;
Form : in String := "");
61/2 Creates zero or more directories with name New_Directory. Each
non-existent directory named by New_Directory is created.[ For
example, on a typical Unix system, Create_Path ("/usr/me/my");
would create directory "me" in directory "usr", then create
directory "my" in directory "me".] The Form parameter can be used
to give system-dependent characteristics of the directory; the
interpretation of the Form parameter is implementation-defined. A
null string for Form specifies the use of the default options of
the implementation of the new directory. The exception Name_Error
is propagated if the string given as New_Directory does not allow
the identification of any directory. The exception Use_Error is
propagated if the external environment does not support the
creation of any directories with the given name (in the absence of
Name_Error) and form.
62/2 procedure Delete_Tree (Directory : in String);
63/2 Deletes an existing directory with name Directory. The directory
and all of its contents (possibly including other directories) are
deleted. The exception Name_Error is propagated if the string
given as Directory does not identify an existing directory. The
exception Use_Error is propagated if the external environment does
not support the deletion of the directory or some portion of its
contents with the given name (in the absence of Name_Error). If
Use_Error is propagated, it is unspecified whether a portion of
the contents of the directory is deleted.
64/2 procedure Delete_File (Name : in String);
65/2 Deletes an existing ordinary or special file with name Name. The
exception Name_Error is propagated if the string given as Name
does not identify an existing ordinary or special external file.
The exception Use_Error is propagated if the external environment
does not support the deletion of the file with the given name (in
the absence of Name_Error).
66/2 procedure Rename (Old_Name, New_Name : in String);
67/2 Renames an existing external file (including directories) with
name Old_Name to New_Name. The exception Name_Error is propagated
if the string given as Old_Name does not identify an existing
external file. The exception Use_Error is propagated if the
external environment does not support the renaming of the file
with the given name (in the absence of Name_Error). In particular,
Use_Error is propagated if a file or directory already exists with
name New_Name.
67.a/2 Implementation Note: This operation is expected to work within a a
single directory, and implementers are encouraged to support it
across directories on a single device. Copying files from one
device to another is discouraged (that's what Copy_File is for).
However, there is no requirement to detect file copying by the
target system. If the target system has an API that gives that for
"free", it can be used. For Windows®, for instance, MoveFile can
be used to implement Rename.
68/2 procedure Copy_File (Source_Name,
Target_Name : in String;
Form : in String);
69/2 Copies the contents of the existing external file with name
Source_Name to an external file with name Target_Name. The
resulting external file is a duplicate of the source external
file. The Form parameter can be used to give system-dependent
characteristics of the resulting external file; the interpretation
of the Form parameter is implementation-defined. Exception
Name_Error is propagated if the string given as Source_Name does
not identify an existing external ordinary or special file, or if
the string given as Target_Name does not allow the identification
of an external file. The exception Use_Error is propagated if the
external environment does not support creating the file with the
name given by Target_Name and form given by Form, or copying of
the file with the name given by Source_Name (in the absence of
Name_Error).
69.a/2 Ramification: Name_Error is always raised if Source_Name
identifies a directory. It is up to the implementation whether
special files can be copied, or if Use_Error will be raised.
70/2 {AI95-00248-01} The following file and directory name operations are
provided:
71/2 function Full_Name (Name : in String) return String;
72/2 Returns the full name corresponding to the file name specified by
Name. The exception Name_Error is propagated if the string given
as Name does not allow the identification of an external file
(including directories and special files).
72.a/2 Discussion: Full name means that no abbreviations are used in the
returned name, and that it is a full specification of the name.
Thus, for Unix and Windows®, the result should be a full path that
does not contain any "." or ".." directories. Typically, the
default directory is used to fill in any missing information.
73/2 function Simple_Name (Name : in String) return String;
74/2 Returns the simple name portion of the file name specified by
Name. The exception Name_Error is propagated if the string given
as Name does not allow the identification of an external file
(including directories and special files).
75/2 function Containing_Directory (Name : in String) return String;
76/2 Returns the name of the containing directory of the external file
(including directories) identified by Name. (If more than one
directory can contain Name, the directory name returned is
implementation-defined.) The exception Name_Error is propagated if
the string given as Name does not allow the identification of an
external file. The exception Use_Error is propagated if the
external file does not have a containing directory.
76.a/2 Discussion: This is purely a string manipulation function. If Name
is not given as a full name, the containing directory probably
won't be one, either. For example, if Containing_Directory
("..\AARM\RM-A-8") is called on Windows®, the result should be
"..\AARM". If there is no path at all on the name, the result
should be "." (which represents the current directory). Use
Full_Name on the result of Containing_Directory if the full name
is needed.
77/2 function Extension (Name : in String) return String;
78/2 Returns the extension name corresponding to Name. The extension
name is a portion of a simple name (not including any separator
characters), typically used to identify the file class. If the
external environment does not have extension names, then the null
string is returned. The exception Name_Error is propagated if the
string given as Name does not allow the identification of an
external file.
78.a/2 Discussion: For Unix and Windows®, the extension is the portion of
the simple name following the rightmost period. For example, in
the simple name "RM-A-8.html", the extension is "html".
79/2 function Base_Name (Name : in String) return String;
80/2 Returns the base name corresponding to Name. The base name is the
remainder of a simple name after removing any extension and
extension separators. The exception Name_Error is propagated if
the string given as Name does not allow the identification of an
external file (including directories and special files).
80.a/2 Discussion: For Unix and Windows®, the base name is the portion of
the simple name preceding the rightmost period (except for the
special directory names "." and "..", whose Base_Name is "." and
".."). For example, in the simple name "RM-A-8.html", the base
name is "RM-A-8".
81/2 function Compose (Containing_Directory : in String := "";
Name : in String;
Extension : in String := "") return String;
82/2 Returns the name of the external file with the specified
Containing_Directory, Name, and Extension. If Extension is the
null string, then Name is interpreted as a simple name; otherwise
Name is interpreted as a base name. The exception Name_Error is
propagated if the string given as Containing_Directory is not null
and does not allow the identification of a directory, or if the
string given as Extension is not null and is not a possible
extension, or if the string given as Name is not a possible simple
name (if Extension is null) or base name (if Extension is
non-null).
82.a/2 Ramification: The above definition implies that if the Extension
is null, for Unix and Windows® no '.' is added to Name.
82.b/2 Discussion: If Name is null, Name_Error should be raised, as
nothing is not a possible simple name or base name.
82.c/2 Generally, Compose(Containing_Directory(F),
Base_Name(F),Extension(F)) = F. However, this is not true on Unix
or Windows® for file names that end with a '.';
Compose(Base_Name("Fooey."),Extension("Fooey.")) = "Fooey". This
is not a problem for Windows®, as the names have the same meaning
with or without the '.', but these are different names for Unix.
Thus, care needs to be taken on Unix; if Extension is null,
Base_Name should be avoided. (That's not usually a problem with
file names generated by a program.)
83/2 {AI95-00248-01} The following file and directory queries and types are
provided:
84/2 type File_Kind is (Directory, Ordinary_File, Special_File);
85/2 The type File_Kind represents the kind of file represented by an
external file or directory.
86/2 type File_Size is range 0 .. implementation-defined;
87/2 The type File_Size represents the size of an external file.
87.a/2 Implementation defined: The maximum value for a file size in
Directories.
88/2 function Exists (Name : in String) return Boolean;
89/2 Returns True if an external file represented by Name exists, and
False otherwise. The exception Name_Error is propagated if the
string given as Name does not allow the identification of an
external file (including directories and special files).
90/2 function Kind (Name : in String) return File_Kind;
91/2 Returns the kind of external file represented by Name. The
exception Name_Error is propagated if the string given as Name
does not allow the identification of an existing external file.
92/2 function Size (Name : in String) return File_Size;
93/2 Returns the size of the external file represented by Name. The
size of an external file is the number of stream elements
contained in the file. If the external file is not an ordinary
file, the result is implementation-defined. The exception
Name_Error is propagated if the string given as Name does not
allow the identification of an existing external file. The
exception Constraint_Error is propagated if the file size is not a
value of type File_Size.
93.a/2 Implementation defined: The result for Directories.Size for a
directory or special file
93.b/2 Discussion: We allow raising Constraint_Error, so that an
implementation for a system with 64-bit file sizes does not need
to support full numerics on 64-bit integers just to implement this
package. Of course, if 64-bit integers are available on such a
system, they should be used when defining type File_Size.
94/2 function Modification_Time (Name : in String) return Ada.Calendar.Time;
95/2 Returns the time that the external file represented by Name was
most recently modified. If the external file is not an ordinary
file, the result is implementation-defined. The exception
Name_Error is propagated if the string given as Name does not
allow the identification of an existing external file. The
exception Use_Error is propagated if the external environment does
not support reading the modification time of the file with the
name given by Name (in the absence of Name_Error).
95.a/2 Implementation defined: The result for
Directories.Modification_Time for a directory or special file.
96/2 {AI95-00248-01} The following directory searching operations and types
are provided:
97/2 type Directory_Entry_Type is limited private;
98/2 The type Directory_Entry_Type represents a single item in a
directory. These items can only be created by the Get_Next_Entry
procedure in this package. Information about the item can be
obtained from the functions declared in this package. A
default-initialized object of this type is invalid; objects
returned from Get_Next_Entry are valid.
99/2 type Filter_Type is array (File_Kind) of Boolean;
100/2 The type Filter_Type specifies which directory entries are
provided from a search operation. If the Directory component is
True, directory entries representing directories are provided. If
the Ordinary_File component is True, directory entries
representing ordinary files are provided. If the Special_File
component is True, directory entries representing special files
are provided.
101/2 type Search_Type is limited private;
102/2 The type Search_Type contains the state of a directory search. A
default-initialized Search_Type object has no entries available
(function More_Entries returns False). Type Search_Type needs
finalization (see 7.6).
103/2 procedure Start_Search (Search : in out Search_Type;
Directory : in String;
Pattern : in String;
Filter : in Filter_Type := (others => True));
104/2 Starts a search in the directory named by Directory for entries
matching Pattern. Pattern represents a pattern for matching file
names. If Pattern is null, all items in the directory are matched;
otherwise, the interpretation of Pattern is
implementation-defined. Only items that match Filter will be
returned. After a successful call on Start_Search, the object
Search may have entries available, but it may have no entries
available if no files or directories match Pattern and Filter. The
exception Name_Error is propagated if the string given by
Directory does not identify an existing directory, or if Pattern
does not allow the identification of any possible external file or
directory. The exception Use_Error is propagated if the external
environment does not support the searching of the directory with
the given name (in the absence of Name_Error). When Start_Search
propagates Name_Error or Use_Error, the object Search will have no
entries available.
104.a/2 Implementation defined: The interpretation of a non-null search
pattern in Directories.
105/2 procedure End_Search (Search : in out Search_Type);
106/2 Ends the search represented by Search. After a successful call on
End_Search, the object Search will have no entries available.
106.a/2 Ramification: The only way that a call to End_Search could be
unsuccessful if Device_Error (see A.13) is raised because of an
underlying failure (or bug).
107/2 function More_Entries (Search : in Search_Type) return Boolean;
108/2 Returns True if more entries are available to be returned by a
call to Get_Next_Entry for the specified search object, and False
otherwise.
109/2 procedure Get_Next_Entry (Search : in out Search_Type;
Directory_Entry : out Directory_Entry_Type);
110/2 Returns the next Directory_Entry for the search described by
Search that matches the pattern and filter. If no further matches
are available, Status_Error is raised. It is
implementation-defined as to whether the results returned by this
routine are altered if the contents of the directory are altered
while the Search object is valid (for example, by another
program). The exception Use_Error is propagated if the external
environment does not support continued searching of the directory
represented by Search.
110.a/2 Implementation defined: The results of a Directories search if the
contents of the directory are altered while a search is in
progress.
111/2 procedure Search (
Directory : in String;
Pattern : in String;
Filter : in Filter_Type := (others => True);
Process : not null access procedure (
Directory_Entry : in Directory_Entry_Type));
112/2 Searches in the directory named by Directory for entries matching
Pattern. The subprogram designated by Process is called with each
matching entry in turn. Pattern represents a pattern for matching
file names. If Pattern is null, all items in the directory are
matched; otherwise, the interpretation of Pattern is
implementation-defined. Only items that match Filter will be
returned. The exception Name_Error is propagated if the string
given by Directory does not identify an existing directory, or if
Pattern does not allow the identification of any possible external
file or directory. The exception Use_Error is propagated if the
external environment does not support the searching of the
directory with the given name (in the absence of Name_Error).
112.a/2 Discussion: "In turn" means that the calls to the subprogram
designated by Process are not made in parallel; they can be made
in any order but must be in sequence.
113/2 function Simple_Name (Directory_Entry : in Directory_Entry_Type)
return String;
114/2 Returns the simple external name of the external file (including
directories) represented by Directory_Entry. The format of the
name returned is implementation-defined. The exception
Status_Error is propagated if Directory_Entry is invalid.
115/2 function Full_Name (Directory_Entry : in Directory_Entry_Type)
return String;
116/2 Returns the full external name of the external file (including
directories) represented by Directory_Entry. The format of the
name returned is implementation-defined. The exception
Status_Error is propagated if Directory_Entry is invalid.
117/2 function Kind (Directory_Entry : in Directory_Entry_Type)
return File_Kind;
118/2 Returns the kind of external file represented by Directory_Entry.
The exception Status_Error is propagated if Directory_Entry is
invalid.
119/2 function Size (Directory_Entry : in Directory_Entry_Type)
return File_Size;
120/2 Returns the size of the external file represented by
Directory_Entry. The size of an external file is the number of
stream elements contained in the file. If the external file
represented by Directory_Entry is not an ordinary file, the result
is implementation-defined. The exception Status_Error is
propagated if Directory_Entry is invalid. The exception
Constraint_Error is propagated if the file size is not a value of
type File_Size.
121/2 function Modification_Time (Directory_Entry : in Directory_Entry_Type)
return Ada.Calendar.Time;
122/2 Returns the time that the external file represented by
Directory_Entry was most recently modified. If the external file
represented by Directory_Entry is not an ordinary file, the result
is implementation-defined. The exception Status_Error is
propagated if Directory_Entry is invalid. The exception Use_Error
is propagated if the external environment does not support reading
the modification time of the file represented by Directory_Entry.
Implementation Requirements
123/2 For Copy_File, if Source_Name identifies an existing external ordinary
file created by a predefined Ada input-output package, and Target_Name and
Form can be used in the Create operation of that input-output package with
mode Out_File without raising an exception, then Copy_File shall not propagate
Use_Error.
123.a/2 Discussion: This means that Copy_File will copy any file that the
Ada programmer could copy (by writing some possibly complicated
Ada code).
Implementation Advice
124/2 If other information about a file (such as the owner or creation date)
is available in a directory entry, the implementation should provide functions
in a child package Directories.Information to retrieve it.
124.a/2 Implementation Advice: Package Directories.Information should be
provided to retrieve other information about a file.
124.b/2 Implementation Note: For Windows®, Directories.Information should
contain at least the following routines:
124.c/2 package Ada.Directories.Information is
-- System-specific directory information.
-- Version for the Microsoft® Windows® operating system.
124.d/2 function Creation_Time (Name : in String) return Ada.Calendar.Time;
124.e/2 function Last_Access_Time (Name : in String) return Ada.Calendar.Time;
124.f/2 function Is_Read_Only (Name : in String) return Boolean;
124.g/2 function Needs_Archiving (Name : in String) return Boolean;
-- This generally means that the file needs to be backed up.
-- The flag is only cleared by backup programs.
124.h/2 function Is_Compressed (Name : in String) return Boolean;
124.i/2 function Is_Encrypted (Name : in String) return Boolean;
124.j/2 function Is_Hidden (Name : in String) return Boolean;
124.k/2 function Is_System (Name : in String) return Boolean;
124.l/2 function Is_Offline (Name : in String) return Boolean;
124.m/2 function Is_Temporary (Name : in String) return Boolean;
124.n/2 function Is_Sparse (Name : in String) return Boolean;
124.o/2 function Is_Not_Indexed (Name : in String) return Boolean;
124.p/2 function Creation_Time (Directory_Entry : in Directory_Entry_Type)
return Ada.Calendar.Time;
124.q/2 function Last_Access_Time (Directory_Entry : in Directory_Entry_Type)
return Ada.Calendar.Time;
124.r/2 function Is_Read_Only (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.s/2 function Needs_Archiving (Directory_Entry : in Directory_Entry_Type) return Boolean;
-- This generally means that the file needs to be backed up.
-- The flag is only cleared by backup programs.
124.t/2 function Is_Compressed (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.u/2 function Is_Encrypted (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.v/2 function Is_Hidden (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.w/2 function Is_System (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.x/2 function Is_Offline (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.y/2 function Is_Temporary (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.z/2 function Is_Sparse (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.aa/2 function Is_Not_Indexed (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.bb/2 -- Additional implementation-defined subprograms allowed here.
end Ada.Directories.Information;
124.cc/2 For Unix-like systems (Unix, POSIX, Linux, etc.),
Directories.Information should contain at least the following
routines:
124.dd/2 package Ada.Directories.Information is
-- System-specific directory information.
-- Unix and similar systems version.
124.ee/2 function Last_Access_Time (Name : in String) return Ada.Calendar.Time;
124.ff/2 function Last_Status_Change_Time (Name : in String) return Ada.Calendar.Time;
124.gg/2 type Permission is
(Others_Execute, Others_Write, Others_Read,
Group_Execute, Group_Write, Group_Read,
Owner_Execute, Owner_Write, Owner_Read,
Set_Group_ID, Set_User_ID);
124.hh/2 type Permission_Set_Type is array (Permission) of Boolean;
124.ii/2 function Permission_Set (Name : in String) return Permission_Set_Type;
124.jj/2 function Owner (Name : in String) return String;
-- Returns the image of the User_Id. If a definition of User_Id
-- is available, an implementation-defined version of Owner
-- returning User_Id should also be defined.
124.kk/2 function Group (Name : in String) return String;
-- Returns the image of the User_Id. If a definition of Group_Id
-- is available, an implementation-defined version of Group
-- returning Group_Id should also be defined.
124.ll/2 function Is_Block_Special_File (Name : in String) return Boolean;
124.mm/2 function Is_Character_Special_File (Name : in String) return Boolean;
124.nn/2 function Is_FIFO (Name : in String) return Boolean;
124.oo/2 function Is_Symbolic_Link (Name : in String) return Boolean;
124.pp/2 function Is_Socket (Name : in String) return Boolean;
124.qq/2 function Last_Access_Time (Directory_Entry : in Directory_Entry_Type)
return Ada.Calendar.Time;
124.rr/2 function Last_Status_Change_Time (Directory_Entry : in Directory_Entry_Type)
return Ada.Calendar.Time;
124.ss/2 function Permission_Set (Directory_Entry : in Directory_Entry_Type)
return Permission_Set_Type;
124.tt/2 function Owner (Directory_Entry : in Directory_Entry_Type) return String;
-- See Owner above.
124.uu/2 function Group (Directory_Entry : in Directory_Entry_Type) return String;
-- See Group above.
124.vv/2 function Is_Block_Special_File (Directory_Entry : in Directory_Entry_Type)
return Boolean;
124.ww/2 function Is_Character_Special_File (Directory_Entry : in Directory_Entry_Type)
return Boolean;
124.xx/2 function Is_FIFO (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.yy/2 function Is_Symbolic_Link (Directory_Entry : in Directory_Entry_Type)
return Boolean;
124.zz/2 function Is_Socket (Directory_Entry : in Directory_Entry_Type) return Boolean;
124.aaa/2 -- Additional implementation-defined subprograms allowed here.
end Ada.Directories.Information;
124.bbb/2 We give these definitions to give guidance so that every
implementation for a given target is not unnecessarily different.
Implementers are encouraged to make packages for other targets as
similar to these as possible.
125/2 Start_Search and Search should raise Use_Error if Pattern is malformed,
but not if it could represent a file in the directory but does not actually do
so.
125.a/2 Implementation Advice: Directories.Start_Search and
Directories.Search should raise Use_Error for malformed patterns.
126/2 Rename should be supported at least when both New_Name and Old_Name are
simple names and New_Name does not identify an existing external file.
126.a/2 Implementation Advice: Directories.Rename should be supported at
least when both New_Name and Old_Name are simple names and
New_Name does not identify an existing external file.
126.b/2 Discussion: "Supported" includes raising an exception if either
name is malformed, the file to rename doesn't exist, insufficient
permission for the operation exists, or similar problems. But this
advice requires implementations to document what they do, and
tells implementers that simply raising Use_Error isn't acceptable.
NOTES
127/2 37 The operations Containing_Directory, Full_Name, Simple_Name,
Base_Name, Extension, and Compose operate on file names, not external
files. The files identified by these operations do not need to exist.
Name_Error is raised only if the file name is malformed and cannot
possibly identify a file. Of these operations, only the result of
Full_Name depends on the current default directory; the result of the
others depends only on their parameters.
128/2 38 Using access types, values of Search_Type and Directory_Entry_Type
can be saved and queried later. However, another task or application
can modify or delete the file represented by a Directory_Entry_Type
value or the directory represented by a Search_Type value; such a
value can only give the information valid at the time it is created.
Therefore, long-term storage of these values is not recommended.
129/2 39 If the target system does not support directories inside of
directories, then Kind will never return Directory and
Containing_Directory will always raise Use_Error.
130/2 40 If the target system does not support creation or deletion of
directories, then Create_Directory, Create_Path, Delete_Directory, and
Delete_Tree will always propagate Use_Error.
131/2 41 To move a file or directory to a different location, use Rename.
Most target systems will allow renaming of files from one directory to
another. If the target file or directory might already exist, it
should be deleted first.
131.a/2 Discussion: While Rename is only guaranteed to work for name
changes within a single directory, its unlikely that implementers
would purposely prevent functionality present in the underlying
system from working. To move a file totally portably, it's
necessary to handle failure of the Rename and fall back to
Copy_File and Delete:
131.b begin
Rename (Source, Target);
exception
when Use_Error =>
Copy_File (Source, Target);
Delete (Source);
end;
Extensions to Ada 95
131.c/2 {AI95-00248-01} {extensions to Ada 95} Package Ada.Directories is
new.
A.17 The Package Environment_Variables
1/2 {AI95-00370-01} {environment variable} The package Environment_Variables
allows a program to read or modify environment variables. Environment
variables are name-value pairs, where both the name and value are strings. The
definition of what constitutes an environment variable, and the meaning of the
name and value, are implementation defined.
1.a/2 Implementation defined: The definition and meaning of an
environment variable.
Static Semantics
2/2 {AI95-00370-01} The library package Environment_Variables has the
following declaration:
3/2 package Ada.Environment_Variables is
pragma Preelaborate(Environment_Variables);
4/2 function Value (Name : in String) return String;
5/2 function Exists (Name : in String) return Boolean;
6/2 procedure Set (Name : in String; Value : in String);
7/2 procedure Clear (Name : in String);
procedure Clear;
8/2 procedure Iterate (
Process : not null access procedure (Name, Value : in String));
9/2 end Ada.Environment_Variables;
10/2 function Value (Name : in String) return String;
11/2 {AI95-00370-01} If the external execution environment supports
environment variables, then Value returns the value of the
environment variable with the given name. If no environment
variable with the given name exists, then Constraint_Error is
propagated. If the execution environment does not support
environment variables, then Program_Error is propagated.
12/2 function Exists (Name : in String) return Boolean;
13/2 {AI95-00370-01} If the external execution environment supports
environment variables and an environment variable with the given
name currently exists, then Exists returns True; otherwise it
returns False.
14/2 procedure Set (Name : in String; Value : in String);
15/2 {AI95-00370-01} If the external execution environment supports
environment variables, then Set first clears any existing
environment variable with the given name, and then defines a
single new environment variable with the given name and value.
Otherwise Program_Error is propagated.
16/2 If implementation-defined circumstances prohibit the definition of
an environment variable with the given name and value, then
Constraint_Error is propagated.
16.a/2 Implementation defined: The circumstances where an environment
variable cannot be defined.
17/2 It is implementation defined whether there exist values for which
the call Set(Name, Value) has the same effect as Clear (Name).
17.a/2 Implementation defined: Environment names for which Set has the
effect of Clear.
18/2 procedure Clear (Name : in String);
19/2 {AI95-00370-01} If the external execution environment supports
environment variables, then Clear deletes all existing environment
variable with the given name. Otherwise Program_Error is
propagated.
20/2 procedure Clear;
21/2 {AI95-00370-01} If the external execution environment supports
environment variables, then Clear deletes all existing environment
variables. Otherwise Program_Error is propagated.
22/2 procedure Iterate (
Process : not null access procedure (Name, Value : in String));
23/2 {AI95-00370-01} If the external execution environment supports
environment variables, then Iterate calls the subprogram
designated by Process for each existing environment variable,
passing the name and value of that environment variable. Otherwise
Program_Error is propagated.
24/2 If several environment variables exist that have the same name,
Process is called once for each such variable.
Bounded (Run-Time) Errors
25/2 {AI95-00370-01} {bounded error (cause) [partial]} It is a bounded error
to call Value if more than one environment variable exists with the given
name; the possible outcomes are that:
26/2 * one of the values is returned, and that same value is returned in
subsequent calls in the absence of changes to the environment; or
27/2 * Program_Error is propagated.
Erroneous Execution
28/2 {AI95-00370-01} {erroneous execution (cause) [partial]} Making calls to
the procedures Set or Clear concurrently with calls to any subprogram of
package Environment_Variables, or to any instantiation of Iterate, results in
erroneous execution.
29/2 Making calls to the procedures Set or Clear in the actual subprogram
corresponding to the Process parameter of Iterate results in erroneous
execution.
Documentation Requirements
30/2 {AI95-00370-01} An implementation shall document how the operations of
this package behave if environment variables are changed by external
mechanisms (for instance, calling operating system services).
30.a/2 Documentation Requirement: The behavior of package
Environment_Variables when environment variables are changed by
external mechanisms.
Implementation Permissions
31/2 {AI95-00370-01} An implementation running on a system that does not
support environment variables is permitted to define the operations of package
Environment_Variables with the semantics corresponding to the case where the
external execution environment does support environment variables. In this
case, it shall provide a mechanism to initialize a nonempty set of environment
variables prior to the execution of a partition.
Implementation Advice
32/2 {AI95-00370-01} If the execution environment supports subprocesses, the
currently defined environment variables should be used to initialize the
environment variables of a subprocess.
32.a/2 Implementation Advice: If the execution environment supports
subprocesses, the current environment variables should be used to
initialize the environment variables of a subprocess.
33/2 Changes to the environment variables made outside the control of this
package should be reflected immediately in the effect of the operations of
this package. Changes to the environment variables made using this package
should be reflected immediately in the external execution environment. This
package should not perform any buffering of the environment variables.
33.a/2 Implementation Advice: Changes to the environment variables made
outside the control of Environment_Variables should be reflected
immediately.
Extensions to Ada 95
33.b/2 {AI95-00370-01} {extensions to Ada 95} Package
Environment_Variables is new.
A.18 Containers
1/2 {AI95-00302-03} This clause presents the specifications of the package
Containers and several child packages, which provide facilities for storing
collections of elements.
2/2 {AI95-00302-03} A variety of sequence and associative containers are
provided. Each container includes a cursor type. A cursor is a reference to an
element within a container. Many operations on cursors are common to all of
the containers. A cursor referencing an element in a container is considered
to be overlapping with the container object itself.{cursor (for a container)
[partial]} {container (cursor)}
2.a/2 Reason: The last sentence is intended to clarify that operations
that just use a cursor are on the same footing as operations that
use a container in terms of the reentrancy rules of Annex A.
3/2 {AI95-00302-03} Within this clause we provide Implementation Advice for
the desired average or worst case time complexity of certain operations on a
container. This advice is expressed using the Landau symbol O(X). Presuming f
is some function of a length parameter N and t(N) is the time the operation
takes (on average or worst case, as specified) for the length N, a complexity
of O(f(N)) means that there exists a finite A such that for any N, t(N)/f(N) <
A. {Landau symbol O(X)} {O(f(N))}
3.a/2 Discussion: Of course, an implementation can do better than a
specified O(f(N)): for example, O(1) meets the requirements for
O(log N).
3.b/2 This concept seems to have as many names as there are authors. We
used "Landau symbol" because that's what our reference does. But
we'd also seen this referred as big-O notation{big-O notation}
(sometimes written as big-oh), and as Bachmann notation. Whatever
the name, it always has the above definition.
4/2 If the advice suggests that the complexity should be less than O(f(N)),
then for any arbitrarily small positive real D, there should exist a positive
integer M such that for all N > M, t(N)/f(N) < D.
Language Design Principles
4.a/2 {AI95-00302-03} This clause provides a number of useful containers
for Ada. Only the most useful containers are provided. Ones that
are relatively easy to code, redundant, or rarely used are omitted
from this set, even if they are generally included in containers
libraries.
4.b/2 The containers packages are modeled on the Standard Template
Library (STL), an algorithms and data structure library
popularized by Alexander Stepanov, and included in the C++
standard library. The structure and terminology differ from the
STL where that better maps to common Ada usage. For instance, what
the STL calls "iterators" are called "cursors" here.
4.c/2 The following major nonlimited containers are provided:
4.d/2 * (Expandable) Vectors of any nonlimited type;
4.e/2 * Doubly-linked Lists of any nonlimited type;
4.f/2 * Hashed Maps keyed by any nonlimited hashable type, and
containing any nonlimited type;
4.g/2 * Ordered Maps keyed by any nonlimited ordered type, and
containing any nonlimited type;
4.h/2 * Hashed Sets of any nonlimited hashable type; and
4.i/2 * Ordered Sets of any nonlimited ordered type.
4.j/2 Separate versions for definite and indefinite element types are
provided, as those for definite types can be implemented more
efficiently.
4.k/2 Each container includes a cursor, which is a reference to an
element within a container. Cursors generally remain valid as long
as the container exists and the element referenced is not deleted.
Many operations on cursors are common to all of the containers.
This makes it possible to write generic algorithms that work on
any kind of container.
4.l/2 The containers packages are structured so that additional packages
can be added in the future. Indeed, we hope that these packages
provide the basis for a more extensive secondary standard for
containers.
4.m/2 If containers with similar functionality (but different
performance characteristics) are provided (by the implementation
or by a secondary standard), we suggest that a prefix be used to
identify the class of the functionality:
"Ada.Containers.Bounded_Sets" (for a set with a maximum number of
elements); "Ada.Containers.Protected_Maps" (for a map which can be
accessed by multiple tasks at one time);
"Ada.Containers.Persistent_Vectors" (for a persistent vector which
continues to exist between executions of a program) and so on.
4.n/2 Note that the language already includes several requirements that
are important to the use of containers. These include:
4.o/2 * Library packages must be reentrant - multiple tasks can use
the packages as long as they operate on separate containers.
Thus, it is only necessary for a user to protect a container
if a single container needs to be used by multiple tasks.
4.p/2 * Language-defined types must stream "properly". That means that
the stream attributes can be used to implement persistence of
containers when necessary, and containers can be passed
between partitions of a program.
4.q/2 * Equality of language-defined types must compose "properly".
This means that the version of "=" directly used by users is
the same one that will be used in generics and in predefined
equality operators of types with components of the containers
and/or cursors. This prevents the abstraction from breaking
unexpectedly.
4.r/2 If a container's element type is controlled, the point at which
the element is finalized will depend on the implementation of the
container. We do not specify precisely where this will happen (it
will happen no later than the finalization of the container, of
course) in order to give implementation's flexibility to cache,
block, or split the nodes of the container. In particular, Delete
does not necessarily finalize the element; the implementation may
(or may not) hold the space for reuse.
4.s/2 This is not likely to be a hardship, as the element type has to be
nonlimited. Types used to manage scarce resources generally need
to be limited. Otherwise, the amount of resources needed is hard
to control, as the language allows a lot of variation in the
number or order of adjusts/finalizations. For common uses of
nonlimited controlled types such as managing storage, the types
already have to manage arbitrary copies.
4.t/2 The use of controlled type also brings up the possibility of
failure of finalization (and thus deallocation) of an element.
This is a "serious bug", as AI-179 puts it, so we don't try to
specify what happens in that case. The implementation should
propagate the exception.
4.u/2 Implementation Note: It is expected that exceptions propagated
from these operations do not damage containers. That is, if
Storage_Error is propagated because of an allocation failure, or
Constraint_Error is propagated by the assignment of elements, the
container can continue to be used without further exceptions. The
intent is that it should be possible to recover from errors
without losing data. We don't try to state this formally in most
cases, because it is hard to define precisely what is and is not
allowed behavior.
4.v/2 Implementation Note: When this clause says that the behavior of
something is unspecified{unspecified [partial]} , we really mean
that any result of executing Ada code short of erroneous execution
is allowed. We do not mean that memory not belonging to the
parameters of the operation can be trashed. When we mean to allow
erroneous behavior, we specifically say that execution is
erroneous. All this means if the containers are written in Ada is
that checks should not be suppressed or removed assuming some
behavior of other code, and that the implementation should take
care to avoid creating internal dangling accesses by assuming
behavior from generic formals that can't be guaranteed. We don't
try to say this normatively because it would be fairly complex,
and implementers are unlikely to increase their support costs by
fielding implementations that are unstable if given buggy hash
functions, et al.
Extensions to Ada 95
4.w/2 {AI95-00302-03} {extensions to Ada 95} This clause is new. It just
provides an introduction to the following subclauses.
A.18.1 The Package Containers
1/2 {AI95-00302-03} The package Containers is the root of the containers
subsystem.
Static Semantics
2/2 {AI95-00302-03} The library package Containers has the following
declaration:
3/2 package Ada.Containers is
pragma Pure(Containers);
4/2 type Hash_Type is mod implementation-defined;
5/2 type Count_Type is range 0 .. implementation-defined;
6/2 end Ada.Containers;
7/2 {AI95-00302-03} Hash_Type represents the range of the result of a hash
function. Count_Type represents the (potential or actual) number of elements
of a container.
7.a/2 Implementation defined: The value of Containers.Hash_Type'Modulus.
The value of Containers.Count_Type'Last.
Implementation Advice
8/2 {AI95-00302-03} Hash_Type'Modulus should be at least 2**32.
Count_Type'Last should be at least 2**31-1.
8.a/2 Implementation Advice: Containers.Hash_Type'Modulus should be at
least 2**32. Containers.Count_Type'Last should be at least 2**31-1.
8.b/2 Discussion: This is not a requirement so that these types can be
declared properly on machines with native sizes that are not 32
bits. For instance, a 24-bit target could use 2**24 for
Hash_Type'Modulus.
Extensions to Ada 95
8.c/2 {AI95-00302-03} {extensions to Ada 95} The package Containers is
new.
A.18.2 The Package Containers.Vectors
1/2 The language-defined generic package Containers.Vectors provides private
types Vector and Cursor, and a set of operations for each type. A vector
container allows insertion and deletion at any position, but it is
specifically optimized for insertion and deletion at the high end (the end
with the higher index) of the container. A vector container also provides
random access to its elements.{vector container} {container (vector)}
2/2 {length (of a vector container) [partial]} {capacity (of a vector)
[partial]} A vector container behaves conceptually as an array that expands
as necessary as items are inserted. The length of a vector is the number of
elements that the vector contains. The capacity of a vector is the maximum
number of elements that can be inserted into the vector prior to it being
automatically expanded.
3/2 Elements in a vector container can be referred to by an index value of a
generic formal type. The first element of a vector always has its index value
equal to the lower bound of the formal type.
4/2 {empty element (of a vector) [partial]} A vector container may contain
empty elements. Empty elements do not have a specified value.
4.a/2 Implementation Note: Vectors are not intended to be sparse (that
is, there are elements at all defined positions). Users are
expected to use other containers (like a Map) when they need
sparse structures (there is a Note to this effect at the end of
this subclause).
4.b/2 The internal array is a conceptual model of a vector. There is no
requirement for an implementation to be a single contiguous array.
Static Semantics
5/2 {AI95-00302-03} The generic library package Containers.Vectors has the
following declaration:
6/2 generic
type Index_Type is range <>;
type Element_Type is private;
with function "=" (Left, Right : Element_Type)
return Boolean is <>;
package Ada.Containers.Vectors is
pragma Preelaborate(Vectors);
7/2 subtype Extended_Index is
Index_Type'Base range
Index_Type'First-1 ..
Index_Type'Min (Index_Type'Base'Last - 1, Index_Type'Last) + 1;
No_Index : constant Extended_Index := Extended_Index'First;
8/2 type Vector is tagged private;
pragma Preelaborable_Initialization(Vector);
9/2 type Cursor is private;
pragma Preelaborable_Initialization(Cursor);
10/2 Empty_Vector : constant Vector;
11/2 No_Element : constant Cursor;
12/2 function "=" (Left, Right : Vector) return Boolean;
13/2 function To_Vector (Length : Count_Type) return Vector;
14/2 function To_Vector
(New_Item : Element_Type;
Length : Count_Type) return Vector;
15/2 function "&" (Left, Right : Vector) return Vector;
16/2 function "&" (Left : Vector;
Right : Element_Type) return Vector;
17/2 function "&" (Left : Element_Type;
Right : Vector) return Vector;
18/2 function "&" (Left, Right : Element_Type) return Vector;
19/2 function Capacity (Container : Vector) return Count_Type;
20/2 procedure Reserve_Capacity (Container : in out Vector;
Capacity : in Count_Type);
21/2 function Length (Container : Vector) return Count_Type;
22/2 procedure Set_Length (Container : in out Vector;
Length : in Count_Type);
23/2 function Is_Empty (Container : Vector) return Boolean;
24/2 procedure Clear (Container : in out Vector);
25/2 function To_Cursor (Container : Vector;
Index : Extended_Index) return Cursor;
26/2 function To_Index (Position : Cursor) return Extended_Index;
27/2 function Element (Container : Vector;
Index : Index_Type)
return Element_Type;
28/2 function Element (Position : Cursor) return Element_Type;
29/2 procedure Replace_Element (Container : in out Vector;
Index : in Index_Type;
New_Item : in Element_Type);
30/2 procedure Replace_Element (Container : in out Vector;
Position : in Cursor;
New_item : in Element_Type);
31/2 procedure Query_Element
(Container : in Vector;
Index : in Index_Type;
Process : not null access procedure (Element : in Element_Type));
32/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Element : in Element_Type));
33/2 procedure Update_Element
(Container : in out Vector;
Index : in Index_Type;
Process : not null access procedure
(Element : in out Element_Type));
34/2 procedure Update_Element
(Container : in out Vector;
Position : in Cursor;
Process : not null access procedure
(Element : in out Element_Type));
35/2 procedure Move (Target : in out Vector;
Source : in out Vector);
36/2 procedure Insert (Container : in out Vector;
Before : in Extended_Index;
New_Item : in Vector);
37/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
New_Item : in Vector);
38/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
New_Item : in Vector;
Position : out Cursor);
39/2 procedure Insert (Container : in out Vector;
Before : in Extended_Index;
New_Item : in Element_Type;
Count : in Count_Type := 1);
40/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
New_Item : in Element_Type;
Count : in Count_Type := 1);
41/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
New_Item : in Element_Type;
Position : out Cursor;
Count : in Count_Type := 1);
42/2 procedure Insert (Container : in out Vector;
Before : in Extended_Index;
Count : in Count_Type := 1);
43/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
Position : out Cursor;
Count : in Count_Type := 1);
44/2 procedure Prepend (Container : in out Vector;
New_Item : in Vector);
45/2 procedure Prepend (Container : in out Vector;
New_Item : in Element_Type;
Count : in Count_Type := 1);
46/2 procedure Append (Container : in out Vector;
New_Item : in Vector);
47/2 procedure Append (Container : in out Vector;
New_Item : in Element_Type;
Count : in Count_Type := 1);
48/2 procedure Insert_Space (Container : in out Vector;
Before : in Extended_Index;
Count : in Count_Type := 1);
49/2 procedure Insert_Space (Container : in out Vector;
Before : in Cursor;
Position : out Cursor;
Count : in Count_Type := 1);
50/2 procedure Delete (Container : in out Vector;
Index : in Extended_Index;
Count : in Count_Type := 1);
51/2 procedure Delete (Container : in out Vector;
Position : in out Cursor;
Count : in Count_Type := 1);
52/2 procedure Delete_First (Container : in out Vector;
Count : in Count_Type := 1);
53/2 procedure Delete_Last (Container : in out Vector;
Count : in Count_Type := 1);
54/2 procedure Reverse_Elements (Container : in out Vector);
55/2 procedure Swap (Container : in out Vector;
I, J : in Index_Type);
56/2 procedure Swap (Container : in out Vector;
I, J : in Cursor);
57/2 function First_Index (Container : Vector) return Index_Type;
58/2 function First (Container : Vector) return Cursor;
59/2 function First_Element (Container : Vector)
return Element_Type;
60/2 function Last_Index (Container : Vector) return Extended_Index;
61/2 function Last (Container : Vector) return Cursor;
62/2 function Last_Element (Container : Vector)
return Element_Type;
63/2 function Next (Position : Cursor) return Cursor;
64/2 procedure Next (Position : in out Cursor);
65/2 function Previous (Position : Cursor) return Cursor;
66/2 procedure Previous (Position : in out Cursor);
67/2 function Find_Index (Container : Vector;
Item : Element_Type;
Index : Index_Type := Index_Type'First)
return Extended_Index;
68/2 function Find (Container : Vector;
Item : Element_Type;
Position : Cursor := No_Element)
return Cursor;
69/2 function Reverse_Find_Index (Container : Vector;
Item : Element_Type;
Index : Index_Type := Index_Type'Last)
return Extended_Index;
70/2 function Reverse_Find (Container : Vector;
Item : Element_Type;
Position : Cursor := No_Element)
return Cursor;
71/2 function Contains (Container : Vector;
Item : Element_Type) return Boolean;
72/2 function Has_Element (Position : Cursor) return Boolean;
73/2 procedure Iterate
(Container : in Vector;
Process : not null access procedure (Position : in Cursor));
74/2 procedure Reverse_Iterate
(Container : in Vector;
Process : not null access procedure (Position : in Cursor));
75/2 generic
with function "<" (Left, Right : Element_Type)
return Boolean is <>;
package Generic_Sorting is
76/2 function Is_Sorted (Container : Vector) return Boolean;
77/2 procedure Sort (Container : in out Vector);
78/2 procedure Merge (Target : in out Vector;
Source : in out Vector);
79/2 end Generic_Sorting;
80/2 private
81/2 ... -- not specified by the language
82/2 end Ada.Containers.Vectors;
83/2 {AI95-00302-03} The actual function for the generic formal function "="
on Element_Type values is expected to define a reflexive and symmetric
relationship and return the same result value each time it is called with a
particular pair of values. If it behaves in some other manner, the functions
defined to use it return an unspecified value. The exact arguments and number
of calls of this generic formal function by the functions defined to use it
are unspecified.{unspecified [partial]}
83.a/2 Ramification: The "functions defined to use it" are Find,
Find_Index, Reverse_Find, Reverse_Find_Index, and "=" for Vectors.
This list is a bit too long to give explicitly.
83.b/2 If the actual function for "=" is not symmetric and consistent,
the result returned by any of the functions defined to use "="
cannot be predicted. The implementation is not required to protect
against "=" raising an exception, or returning random results, or
any other "bad" behavior. And it can call "=" in whatever manner
makes sense. But note that only the results of the functions
defined to use "=" are unspecified; other subprograms are not
allowed to break if "=" is bad.
84/2 {AI95-00302-03} The type Vector is used to represent vectors. The type
Vector needs finalization (see 7.6).
85/2 {AI95-00302-03} Empty_Vector represents the empty vector object. It has a
length of 0. If an object of type Vector is not otherwise initialized, it is
initialized to the same value as Empty_Vector.
86/2 {AI95-00302-03} No_Element represents a cursor that designates no
element. If an object of type Cursor is not otherwise initialized, it is
initialized to the same value as No_Element.
87/2 {AI95-00302-03} The predefined "=" operator for type Cursor returns True
if both cursors are No_Element, or designate the same element in the same
container.
88/2 {AI95-00302-03} Execution of the default implementation of the Input,
Output, Read, or Write attribute of type Cursor raises Program_Error.
88.a/2 Reason: A cursor will probably be implemented in terms of one or
more access values, and the effects of streaming access values is
unspecified. Rather than letting the user stream junk by accident,
we mandate that streaming of cursors raise Program_Error by
default. The attributes can always be specified if there is a need
to support streaming.
89/2 {AI95-00302-03} No_Index represents a position that does not correspond
to any element. The subtype Extended_Index includes the indices covered by
Index_Type plus the value No_Index and, if it exists, the successor to the
Index_Type'Last.
89.a/2 Discussion: We require the existence of Index_Type'First - 1, so
that No_Index and Last_Index of an empty vector is well-defined.
We don't require the existence of Index_Type'Last + 1, as it is
only used as the position of insertions (and needs to be allowed
only when inserting an empty vector).
90/2 {AI95-00302-03} [Some operations of this generic package have
access-to-subprogram parameters. To ensure such operations are well-defined,
they guard against certain actions by the designated subprogram. In
particular, some operations check for "tampering with cursors" of a container
because they depend on the set of elements of the container remaining
constant, and others check for "tampering with elements" of a container
because they depend on elements of the container not being replaced.]
91/2 {AI95-00302-03} {tamper with cursors (of a vector)} A subprogram is said
to tamper with cursors of a vector object V if:
92/2 * it inserts or deletes elements of V, that is, it calls the Insert,
Insert_Space, Clear, Delete, or Set_Length procedures with V as a
parameter; or
92.a/2 To be honest: Operations which are defined to be equivalent to a
call on one of these operations also are included. Similarly,
operations which call one of these as part of their definition are
included.
93/2 * it finalizes V; or
94/2 * it calls the Move procedure with V as a parameter.
94.a/2 Discussion: Swap, Sort, and Merge copy elements rather than
reordering them, so they don't tamper with cursors.
95/2 {AI95-00302-03} {tamper with elements (of a vector)} A subprogram is said
to tamper with elements of a vector object V if:
96/2 * it tampers with cursors of V; or
97/2 * it replaces one or more elements of V, that is, it calls the
Replace_Element, Reverse_Elements, or Swap procedures or the Sort or
Merge procedures of an instance of Generic_Sorting with V as a
parameter.
97.a/2 Reason: Complete replacement of an element can cause its memory to
be deallocated while another operation is holding onto a reference
to it. That can't be allowed. However, a simple modification of
(part of) an element is not a problem, so Update_Element does not
cause a problem.
98/2 function "=" (Left, Right : Vector) return Boolean;
99/2 {AI95-00302-03} If Left and Right denote the same vector object,
then the function returns True. If Left and Right have different
lengths, then the function returns False. Otherwise, it compares
each element in Left to the corresponding element in Right using
the generic formal equality operator. If any such comparison
returns False, the function returns False; otherwise it returns
True. Any exception raised during evaluation of element equality
is propagated.
99.a/2 Implementation Note: This wording describes the canonical
semantics. However, the order and number of calls on the formal
equality function is unspecified for all of the operations that
use it in this package, so an implementation can call it as many
or as few times as it needs to get the correct answer.
Specifically, there is no requirement to call the formal equality
additional times once the answer has been determined.
100/2 function To_Vector (Length : Count_Type) return Vector;
101/2 {AI95-00302-03} Returns a vector with a length of Length, filled
with empty elements.
102/2 function To_Vector
(New_Item : Element_Type;
Length : Count_Type) return Vector;
103/2 {AI95-00302-03} Returns a vector with a length of Length, filled
with elements initialized to the value New_Item.
104/2 function "&" (Left, Right : Vector) return Vector;
105/2 {AI95-00302-03} Returns a vector comprising the elements of Left
followed by the elements of Right.
106/2 function "&" (Left : Vector;
Right : Element_Type) return Vector;
107/2 {AI95-00302-03} Returns a vector comprising the elements of Left
followed by the element Right.
108/2 function "&" (Left : Element_Type;
Right : Vector) return Vector;
109/2 {AI95-00302-03} Returns a vector comprising the element Left
followed by the elements of Right.
110/2 function "&" (Left, Right : Element_Type) return Vector;
111/2 {AI95-00302-03} Returns a vector comprising the element Left
followed by the element Right.
112/2 function Capacity (Container : Vector) return Count_Type;
113/2 {AI95-00302-03} Returns the capacity of Container.
114/2 procedure Reserve_Capacity (Container : in out Vector;
Capacity : in Count_Type);
115/2 {AI95-00302-03} Reserve_Capacity allocates new internal data
structures such that the length of the resulting vector can become
at least the value Capacity without requiring an additional call
to Reserve_Capacity, and is large enough to hold the current
length of Container. Reserve_Capacity then copies the elements
into the new data structures and deallocates the old data
structures. Any exception raised during allocation is propagated
and Container is not modified.
115.a/2 Discussion: Expanding the internal array can be done by allocating
a new, longer array, copying the elements, and deallocating the
original array. This may raise Storage_Error, or cause an
exception from a controlled subprogram. We require that a failed
Reserve_Capacity does not lose any elements if an exception
occurs, but we do not require a specific order of evaluations or
copying.
115.b/2 This routine is used to preallocate the internal array to the
specified capacity such that future Inserts do not require memory
allocation overhead. Therefore, the implementation should allocate
the needed memory to make that true at this point, even though the
visible semantics could be preserved by waiting until the memory
is needed. This doesn't apply to the indefinite element container,
because elements will have to be allocated individually.
115.c/2 The implementation does not have to contract the internal array if
the capacity is reduced, as any capacity greater than or equal to
the specified capacity is allowed.
116/2 function Length (Container : Vector) return Count_Type;
117/2 {AI95-00302-03} Returns the number of elements in Container.
118/2 procedure Set_Length (Container : in out Vector;
Length : in Count_Type);
119/2 {AI95-00302-03} If Length is larger than the capacity of
Container, Set_Length calls Reserve_Capacity (Container, Length),
then sets the length of the Container to Length. If Length is
greater than the original length of Container, empty elements are
added to Container; otherwise elements are removed from Container.
119.a/2 Ramification: No elements are moved by this operation; any new
empty elements are added at the end. This follows from the rules
that a cursor continues to designate the same element unless the
routine is defined to make the cursor ambiguous or invalid; this
operation does not do that.
120/2 function Is_Empty (Container : Vector) return Boolean;
121/2 {AI95-00302-03} Equivalent to Length (Container) = 0.
122/2 procedure Clear (Container : in out Vector);
123/2 {AI95-00302-03} Removes all the elements from Container. The
capacity of Container does not change.
124/2 function To_Cursor (Container : Vector;
Index : Extended_Index) return Cursor;
125/2 {AI95-00302-03} If Index is not in the range First_Index
(Container) .. Last_Index (Container), then No_Element is
returned. Otherwise, a cursor designating the element at position
Index in Container is returned.
126/2 function To_Index (Position : Cursor) return Extended_Index;
127/2 {AI95-00302-03} If Position is No_Element, No_Index is returned.
Otherwise, the index (within its containing vector) of the element
designated by Position is returned.
127.a/2 Ramification: This implies that the index is determinable from a
bare cursor alone. The basic model is that a vector cursor is
implemented as a record containing an access to the vector
container and an index value. This does constrain implementations,
but it also allows all of the cursor operations to be defined in
terms of the corresponding index operation (which should be
primary for a vector).
128/2 function Element (Container : Vector;
Index : Index_Type)
return Element_Type;
129/2 {AI95-00302-03} If Index is not in the range First_Index
(Container) .. Last_Index (Container), then Constraint_Error is
propagated. Otherwise, Element returns the element at position
Index.
130/2 function Element (Position : Cursor) return Element_Type;
131/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. Otherwise, Element returns the
element designated by Position.
132/2 procedure Replace_Element (Container : in out Vector;
Index : in Index_Type;
New_Item : in Element_Type);
133/2 {AI95-00302-03} If Index is not in the range First_Index
(Container) .. Last_Index (Container), then Constraint_Error is
propagated. Otherwise Replace_Element assigns the value New_Item
to the element at position Index. Any exception raised during the
assignment is propagated. The element at position Index is not an
empty element after successful call to Replace_Element.
134/2 procedure Replace_Element (Container : in out Vector;
Position : in Cursor;
New_Item : in Element_Type);
135/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated; if Position does not designate an
element in Container, then Program_Error is propagated. Otherwise
Replace_Element assigns New_Item to the element designated by
Position. Any exception raised during the assignment is
propagated. The element at Position is not an empty element after
successful call to Replace_Element.
135.a/2 Ramification: Replace_Element and Update_Element are the only ways
that an element can change from empty to non-empty. Also see the
note following Update_Element.
136/2 procedure Query_Element
(Container : in Vector;
Index : in Index_Type;
Process : not null access procedure (Element : in Element_Type));
137/2 {AI95-00302-03} If Index is not in the range First_Index
(Container) .. Last_Index (Container), then Constraint_Error is
propagated. Otherwise, Query_Element calls Process.all with the
element at position Index as the argument. Program_Error is
propagated if Process.all tampers with the elements of Container.
Any exception raised by Process.all is propagated.
137.a/2 Reason: The "tamper with the elements" check is intended to
prevent the Element parameter of Process from being modified or
deleted outside of Process. The check prevents data loss (if
Element_Type is passed by copy) or erroneous execution (if
Element_Type is an unconstrained type in an indefinite container).
138/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Element : in Element_Type));
139/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. Otherwise, Query_Element calls
Process.all with the element designated by Position as the
argument. Program_Error is propagated if Process.all tampers with
the elements of Container. Any exception raised by Process.all is
propagated.
140/2 procedure Update_Element
(Container : in out Vector;
Index : in Index_Type;
Process : not null access procedure (Element : in out Element_Type));
141/2 {AI95-00302-03} If Index is not in the range First_Index
(Container) .. Last_Index (Container), then Constraint_Error is
propagated. Otherwise, Update_Element calls Process.all with the
element at position Index as the argument. Program_Error is
propagated if Process.all tampers with the elements of Container.
Any exception raised by Process.all is propagated.
142/2 If Element_Type is unconstrained and definite, then the actual
Element parameter of Process.all shall be unconstrained.
142.a/2 Ramification: This means that the elements cannot be directly
allocated from the heap; it must be possible to change the
discriminants of the element in place.
143/2 The element at position Index is not an empty element after
successful completion of this operation.
143.a/2 Ramification: Since reading an empty element is a bounded error,
attempting to use this procedure to replace empty elements may
fail. Use Replace_Element to do that reliably.
144/2 procedure Update_Element
(Container : in out Vector;
Position : in Cursor;
Process : not null access procedure (Element : in out Element_Type));
145/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated; if Position does not designate an
element in Container, then Program_Error is propagated. Otherwise
Update_Element calls Process.all with the element designated by
Position as the argument. Program_Error is propagated if
Process.all tampers with the elements of Container. Any exception
raised by Process.all is propagated.
146/2 If Element_Type is unconstrained and definite, then the actual
Element parameter of Process.all shall be unconstrained.
147/2 The element designated by Position is not an empty element after
successful completion of this operation.
148/2 procedure Move (Target : in out Vector;
Source : in out Vector);
149/2 {AI95-00302-03} If Target denotes the same object as Source, then
Move has no effect. Otherwise, Move first calls Clear (Target);
then, each element from Source is removed from Source and inserted
into Target in the original order. The length of Source is 0 after
a successful call to Move.
149.a/2 Discussion: The idea is that the internal array is removed from
Source and moved to Target. (See the Implementation Advice for
Move). If Capacity (Target) /= 0, the previous internal array may
need to be deallocated. We don't mention this explicitly, because
it is covered by the "no memory loss" Implementation Requirement.
150/2 procedure Insert (Container : in out Vector;
Before : in Extended_Index;
New_Item : in Vector);
151/2 {AI95-00302-03} If Before is not in the range First_Index
(Container) .. Last_Index (Container) + 1, then Constraint_Error
is propagated. If Length(New_Item) is 0, then Insert does nothing.
Otherwise, it computes the new length NL as the sum of the current
length and Length (New_Item); if the value of Last appropriate for
length NL would be greater than Index_Type'Last then
Constraint_Error is propagated.
152/2 If the current vector capacity is less than NL, Reserve_Capacity
(Container, NL) is called to increase the vector capacity. Then
Insert slides the elements in the range Before .. Last_Index
(Container) up by Length(New_Item) positions, and then copies the
elements of New_Item to the positions starting at Before. Any
exception raised during the copying is propagated.
152.a/2 Ramification: Moving the elements does not necessarily involve
copying. Similarly, since Reserve_Capacity does not require the
copying of elements, it does not need to be explicitly called (the
implementation can combine the operations if it wishes to).
153/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
New_Item : in Vector);
154/2 {AI95-00302-03} If Before is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. Otherwise, if Length(New_Item) is 0, then Insert does
nothing. If Before is No_Element, then the call is equivalent to
Insert (Container, Last_Index (Container) + 1, New_Item);
otherwise the call is equivalent to Insert (Container, To_Index
(Before), New_Item);
154.a/2 Ramification: The check on Before checks that the cursor does not
belong to some other Container. This check implies that a
reference to the container is included in the cursor value. This
wording is not meant to require detection of dangling cursors;
such cursors are defined to be invalid, which means that execution
is erroneous, and any result is allowed (including not raising an
exception).
155/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
New_Item : in Vector;
Position : out Cursor);
156/2 {AI95-00302-03} If Before is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. If Before equals No_Element, then let T be Last_Index
(Container) + 1; otherwise, let T be To_Index (Before). Insert
(Container, T, New_Item) is called, and then Position is set to
To_Cursor (Container, T).
156.a/2 Discussion: The messy wording is needed because Before is
invalidated by Insert, and we don't want Position to be invalid
after this call. An implementation probably only needs to copy
Before to Position.
157/2 procedure Insert (Container : in out Vector;
Before : in Extended_Index;
New_Item : in Element_Type;
Count : in Count_Type := 1);
158/2 {AI95-00302-03} Equivalent to Insert (Container, Before, To_Vector
(New_Item, Count));
159/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
New_Item : in Element_Type;
Count : in Count_Type := 1);
160/2 {AI95-00302-03} Equivalent to Insert (Container, Before, To_Vector
(New_Item, Count));
161/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
New_Item : in Element_Type;
Position : out Cursor;
Count : in Count_Type := 1);
162/2 {AI95-00302-03} Equivalent to Insert (Container, Before, To_Vector
(New_Item, Count), Position);
163/2 procedure Insert (Container : in out Vector;
Before : in Extended_Index;
Count : in Count_Type := 1);
164/2 {AI95-00302-03} If Before is not in the range First_Index
(Container) .. Last_Index (Container) + 1, then Constraint_Error
is propagated. If Count is 0, then Insert does nothing. Otherwise,
it computes the new length NL as the sum of the current length and
Count; if the value of Last appropriate for length NL would be
greater than Index_Type'Last then Constraint_Error is propagated.
165/2 If the current vector capacity is less than NL, Reserve_Capacity
(Container, NL) is called to increase the vector capacity. Then
Insert slides the elements in the range Before .. Last_Index
(Container) up by Count positions, and then inserts elements that
are initialized by default (see 3.3.1) in the positions starting
at Before.
166/2 procedure Insert (Container : in out Vector;
Before : in Cursor;
Position : out Cursor;
Count : in Count_Type := 1);
167/2 {AI95-00302-03} If Before is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. If Before equals No_Element, then let T be Last_Index
(Container) + 1; otherwise, let T be To_Index (Before). Insert
(Container, T, Count) is called, and then Position is set to
To_Cursor (Container, T).
167.a/2 Reason: This routine exists mainly to ease conversion between
Vector and List containers. Unlike Insert_Space, this routine
default initializes the elements it inserts, which can be more
expensive for some element types.
168/2 procedure Prepend (Container : in out Vector;
New_Item : in Vector;
Count : in Count_Type := 1);
169/2 {AI95-00302-03} Equivalent to Insert (Container, First_Index
(Container), New_Item).
170/2 procedure Prepend (Container : in out Vector;
New_Item : in Element_Type;
Count : in Count_Type := 1);
171/2 {AI95-00302-03} Equivalent to Insert (Container, First_Index
(Container), New_Item, Count).
172/2 procedure Append (Container : in out Vector;
New_Item : in Vector);
173/2 {AI95-00302-03} Equivalent to Insert (Container, Last_Index
(Container) + 1, New_Item).
174/2 procedure Append (Container : in out Vector;
New_Item : in Element_Type;
Count : in Count_Type := 1);
175/2 {AI95-00302-03} Equivalent to Insert (Container, Last_Index
(Container) + 1, New_Item, Count).
176/2 procedure Insert_Space (Container : in out Vector;
Before : in Extended_Index;
Count : in Count_Type := 1);
177/2 {AI95-00302-03} If Before is not in the range First_Index
(Container) .. Last_Index (Container) + 1, then Constraint_Error
is propagated. If Count is 0, then Insert_Space does nothing.
Otherwise, it computes the new length NL as the sum of the current
length and Count; if the value of Last appropriate for length NL
would be greater than Index_Type'Last then Constraint_Error is
propagated.
178/2 If the current vector capacity is less than NL, Reserve_Capacity
(Container, NL) is called to increase the vector capacity. Then
Insert_Space slides the elements in the range Before .. Last_Index
(Container) up by Count positions, and then inserts empty elements
in the positions starting at Before.
179/2 procedure Insert_Space (Container : in out Vector;
Before : in Cursor;
Position : out Cursor;
Count : in Count_Type := 1);
180/2 {AI95-00302-03} If Before is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. If Before equals No_Element, then let T be Last_Index
(Container) + 1; otherwise, let T be To_Index (Before).
Insert_Space (Container, T, Count) is called, and then Position is
set to To_Cursor (Container, T).
181/2 procedure Delete (Container : in out Vector;
Index : in Extended_Index;
Count : in Count_Type := 1);
182/2 {AI95-00302-03} If Index is not in the range First_Index
(Container) .. Last_Index (Container) + 1, then Constraint_Error
is propagated. If Count is 0, Delete has no effect. Otherwise
Delete slides the elements (if any) starting at position Index +
Count down to Index. Any exception raised during element
assignment is propagated.
182.a/2 Ramification: If Index + Count >= Last_Index(Container), this
effectively truncates the vector (setting Last_Index to Index - 1
and consequently sets Length to Index - Index_Type'First).
183/2 procedure Delete (Container : in out Vector;
Position : in out Cursor;
Count : in Count_Type := 1);
184/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. If Position does not designate an
element in Container, then Program_Error is propagated. Otherwise,
Delete (Container, To_Index (Position), Count) is called, and then
Position is set to No_Element.
185/2 procedure Delete_First (Container : in out Vector;
Count : in Count_Type := 1);
186/2 {AI95-00302-03} Equivalent to Delete (Container, First_Index
(Container), Count).
187/2 procedure Delete_Last (Container : in out Vector;
Count : in Count_Type := 1);
188/2 {AI95-00302-03} If Length (Container) <= Count then Delete_Last is
equivalent to Clear (Container). Otherwise it is equivalent to
Delete (Container, Index_Type'Val(Index_Type'Pos(Last_Index
(Container)) - Count + 1), Count).
189/2 procedure Reverse_Elements (Container : in out List);
190/2 {AI95-00302-03} Reorders the elements of Container in reverse
order.
190.a/2 Discussion: This can copy the elements of the vector - all cursors
referencing the vector are ambiguous afterwards and may designate
different elements afterwards.
191/2 procedure Swap (Container : in out Vector;
I, J : in Index_Type);
192/2 {AI95-00302-03} If either I or J is not in the range First_Index
(Container) .. Last_Index (Container), then Constraint_Error is
propagated. Otherwise, Swap exchanges the values of the elements
at positions I and J.
192.a/2 To be honest: The implementation is not required to actually copy
the elements if it can do the swap some other way. But it is
allowed to copy the elements if needed.
193/2 procedure Swap (Container : in out Vector;
I, J : in Cursor);
194/2 {AI95-00302-03} If either I or J is No_Element, then
Constraint_Error is propagated. If either I or J do not designate
an element in Container, then Program_Error is propagated.
Otherwise, Swap exchanges the values of the elements designated by
I and J.
194.a/2 Ramification: After a call to Swap, I designates the element value
previously designated by J, and J designates the element value
previously designated by I. The cursors do not become ambiguous
from this operation.
194.b/2 To be honest: The implementation is not required to actually copy
the elements if it can do the swap some other way. But it is
allowed to copy the elements if needed.
195/2 function First_Index (Container : Vector) return Index_Type;
196/2 {AI95-00302-03} Returns the value Index_Type'First.
196.a/2 Discussion: We'd rather call this "First", but then calling most
routines in here with First (Some_Vect) would be ambiguous.
197/2 function First (Container : Vector) return Cursor;
198/2 {AI95-00302-03} If Container is empty, First returns No_Element.
Otherwise, it returns a cursor that designates the first element
in Container.
199/2 function First_Element (Container : Vector) return Element_Type;
200/2 {AI95-00302-03} Equivalent to Element (Container, First_Index
(Container)).
201/2 function Last_Index (Container : Vector) return Extended_Index;
202/2 {AI95-00302-03} If Container is empty, Last_Index returns
No_Index. Otherwise, it returns the position of the last element
in Container.
203/2 function Last (Container : Vector) return Cursor;
204/2 {AI95-00302-03} If Container is empty, Last returns No_Element.
Otherwise, it returns a cursor that designates the last element in
Container.
205/2 function Last_Element (Container : Vector) return Element_Type;
206/2 {AI95-00302-03} Equivalent to Element (Container, Last_Index
(Container)).
207/2 function Next (Position : Cursor) return Cursor;
208/2 {AI95-00302-03} If Position equals No_Element or designates the
last element of the container, then Next returns the value
No_Element. Otherwise, it returns a cursor that designates the
element with index To_Index (Position) + 1 in the same vector as
Position.
209/2 procedure Next (Position : in out Cursor);
210/2 {AI95-00302-03} Equivalent to Position := Next (Position).
211/2 function Previous (Position : Cursor) return Cursor;
212/2 {AI95-00302-03} If Position equals No_Element or designates the
first element of the container, then Previous returns the value
No_Element. Otherwise, it returns a cursor that designates the
element with index To_Index (Position) - 1 in the same vector as
Position.
213/2 procedure Previous (Position : in out Cursor);
214/2 {AI95-00302-03} Equivalent to Position := Previous (Position).
215/2 function Find_Index (Container : Vector;
Item : Element_Type;
Index : Index_Type := Index_Type'First)
return Extended_Index;
216/2 {AI95-00302-03} Searches the elements of Container for an element
equal to Item (using the generic formal equality operator). The
search starts at position Index and proceeds towards Last_Index
(Container). If no equal element is found, then Find_Index returns
No_Index. Otherwise, it returns the index of the first equal
element encountered.
217/2 function Find (Container : Vector;
Item : Element_Type;
Position : Cursor := No_Element)
return Cursor;
218/2 {AI95-00302-03} If Position is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. Otherwise Find searches the elements of Container for
an element equal to Item (using the generic formal equality
operator). The search starts at the first element if Position
equals No_Element, and at the element designated by Position
otherwise. It proceeds towards the last element of Container. If
no equal element is found, then Find returns No_Element.
Otherwise, it returns a cursor designating the first equal element
encountered.
219/2 function Reverse_Find_Index (Container : Vector;
Item : Element_Type;
Index : Index_Type := Index_Type'Last)
return Extended_Index;
220/2 {AI95-00302-03} Searches the elements of Container for an element
equal to Item (using the generic formal equality operator). The
search starts at position Index or, if Index is greater than
Last_Index (Container), at position Last_Index (Container). It
proceeds towards First_Index (Container). If no equal element is
found, then Reverse_Find_Index returns No_Index. Otherwise, it
returns the index of the first equal element encountered.
221/2 function Reverse_Find (Container : Vector;
Item : Element_Type;
Position : Cursor := No_Element)
return Cursor;
222/2 {AI95-00302-03} If Position is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. Otherwise Reverse_Find searches the elements of
Container for an element equal to Item (using the generic formal
equality operator). The search starts at the last element if
Position equals No_Element, and at the element designated by
Position otherwise. It proceeds towards the first element of
Container. If no equal element is found, then Reverse_Find returns
No_Element. Otherwise, it returns a cursor designating the first
equal element encountered.
223/2 function Contains (Container : Vector;
Item : Element_Type) return Boolean;
224/2 {AI95-00302-03} Equivalent to Has_Element (Find (Container, Item)).
225/2 function Has_Element (Position : Cursor) return Boolean;
226/2 {AI95-00302-03} Returns True if Position designates an element,
and returns False otherwise.
226.a/2 To be honest: This function may not detect cursors that designate
deleted elements; such cursors are invalid (see below) and the
result of calling Has_Element with an invalid cursor is
unspecified (but not erroneous).
227/2 procedure Iterate
(Container : in Vector;
Process : not null access procedure (Position : in Cursor));
228/2 {AI95-00302-03} Invokes Process.all with a cursor that designates
each element in Container, in index order. Program_Error is
propagated if Process.all tampers with the cursors of Container.
Any exception raised by Process is propagated.
228.a/2 Discussion: The purpose of the "tamper with the cursors" check is
to prevent erroneous execution from the Position parameter of
Process.all becoming invalid. This check takes place when the
operations that tamper with the cursors of the container are
called. The check cannot be made later (say in the body of
Iterate), because that could cause the Position cursor to be
invalid and potentially cause execution to become erroneous --
defeating the purpose of the check.
228.b/2 There is no check needed if an attempt is made to insert or delete
nothing (that is, Count = 0 or Length(Item) = 0).
228.c/2 The check is easy to implement: each container needs a counter.
The counter is incremented when Iterate is called, and decremented
when Iterate completes. If the counter is nonzero when an
operation that inserts or deletes is called, Finalize is called,
or one of the other operations in the list occurs, Program_Error
is raised.
229/2 procedure Reverse_Iterate
(Container : in Vector;
Process : not null access procedure (Position : in Cursor));
230/2 {AI95-00302-03} Iterates over the elements in Container as per
Iterate, except that elements are traversed in reverse index order.
231/2 The actual function for the generic formal function "<" of
Generic_Sorting is expected to return the same value each time it is called
with a particular pair of element values. It should define a strict ordering
relationship, that is, be irreflexive, asymmetric, and transitive; it should
not modify Container. If the actual for "<" behaves in some other manner, the
behavior of the subprograms of Generic_Sorting are unspecified. How many times
the subprograms of Generic_Sorting call "<" is unspecified.{unspecified
[partial]}
232/2 function Is_Sorted (Container : Vector) return Boolean;
233/2 {AI95-00302-03} Returns True if the elements are sorted smallest
first as determined by the generic formal "<" operator; otherwise,
Is_Sorted returns False. Any exception raised during evaluation of
"<" is propagated.
234/2 procedure Sort (Container : in out Vector);
235/2 {AI95-00302-03} Reorders the elements of Container such that the
elements are sorted smallest first as determined by the generic
formal "<" operator provided. Any exception raised during
evaluation of "<" is propagated.
235.a/2 Ramification: This implies swapping the elements, usually
including an intermediate copy. This means that the elements will
usually be copied. (As with Swap, if the implementation can do
this some other way, it is allowed to.) Since the elements are
nonlimited, this usually will not be a problem. Note that there is
Implementation Advice below that the implementation should use a
sort that minimizes copying of elements.
235.b/2 The sort is not required to be stable (and the fast algorithm
required will not be stable). If a stable sort is needed, the user
can include the original location of the element as an extra "sort
key". We considered requiring the implementation to do that, but
it is mostly extra overhead -- usually there is something already
in the element that provides the needed stability.
236/2 procedure Merge (Target : in out Vector;
Source : in out Vector);
237/2 {AI95-00302-03} Merge removes elements from Source and inserts
them into Target; afterwards, Target contains the union of the
elements that were initially in Source and Target; Source is left
empty. If Target and Source are initially sorted smallest first,
then Target is ordered smallest first as determined by the generic
formal "<" operator; otherwise, the order of elements in Target is
unspecified. Any exception raised during evaluation of "<" is
propagated.
237.a/2 Discussion: It is a bounded error if either of the vectors is
unsorted, see below. The bounded error can be recovered by sorting
Target after the merge call, or the vectors can be pretested with
Is_Sorted.
237.b/2 Implementation Note: The Merge operation will usually require
copying almost all of the elements. One implementation strategy
would be to extend Target to the appropriate length, then copying
elements from the back of the vectors working towards the front.
An alternative approach would be to allocate a new internal data
array of the appropriate length, copy the elements into it in an
appropriate order, and then replacing the data array in Target
with the temporary.
Bounded (Run-Time) Errors
238/2 {AI95-00302-03} {bounded error (cause) [partial]} Reading the value of
an empty element by calling Element, Query_Element, Update_Element, Swap,
Is_Sorted, Sort, Merge, "=", Find, or Reverse_Find is a bounded error. The
implementation may treat the element as having any normal value (see 13.9.1)
of the element type, or raise Constraint_Error or Program_Error before
modifying the vector.
238.a/2 Ramification: For instance, a default initialized element could be
returned. Or some previous value of an element. But returning
random junk is not allowed if the type has default initial
value(s).
238.b/2 Assignment and streaming of empty elements are not bounded errors.
This is consistent with regular composite types, for which
assignment and streaming of uninitialized components do not cause
a bounded error, but reading the uninitialized component does
cause a bounded error.
238.c/2 There are other operations which are defined in terms of the
operations listed above.
239/2 {AI95-00302-03} {bounded error (cause) [partial]} Calling Merge in an
instance of Generic_Sorting with either Source or Target not ordered smallest
first using the provided generic formal "<" operator is a bounded error.
Either Program_Error is raised after Target is updated as described for Merge,
or the operation works as defined.
240/2 {AI95-00302-03} {ambiguous cursor (of a vector)} {cursor (ambiguous)} A
Cursor value is ambiguous if any of the following have occurred since it was
created:
241/2 * Insert, Insert_Space, or Delete has been called on the vector that
contains the element the cursor designates with an index value (or a
cursor designating an element at such an index value) less than or
equal to the index value of the element designated by the cursor; or
242/2 * The vector that contains the element it designates has been passed
to the Sort or Merge procedures of an instance of Generic_Sorting, or
to the Reverse_Elements procedure.
243/2 {AI95-00302-03} {bounded error (cause) [partial]} It is a bounded error
to call any subprogram other than "=" or Has_Element declared in
Containers.Vectors with an ambiguous (but not invalid, see below) cursor
parameter. Possible results are:
244/2 * The cursor may be treated as if it were No_Element;
245/2 * The cursor may designate some element in the vector (but not
necessarily the element that it originally designated);
246/2 * Constraint_Error may be raised; or
247/2 * Program_Error may be raised.
247.a/2 Reason: Cursors are made ambiguous if an Insert or Delete occurs
that moves the elements in the internal array including the
designated ones. After such an operation, the cursor probably
still designates an element (although it might not after a
deletion), but it is a different element. That violates the
definition of cursor - it designates a particular element.
247.b/2 For "=" or Has_Element, the cursor works normally (it would not be
No_Element). We don't want to trigger an exception simply for
comparing a bad cursor.
247.c/2 While it is possible to check for these cases or ensure that
cursors survive such operations, in many cases the overhead
necessary to make the check (or ensure cursors continue to
designate the same element) is substantial in time or space.
Erroneous Execution
248/2 {AI95-00302-03} A Cursor value is invalid if any of the following have
occurred since it was created:{invalid cursor (of a vector)}
{cursor (invalid) [partial]}
249/2 * The vector that contains the element it designates has been
finalized;
250/2 * The vector that contains the element it designates has been used as
the Source or Target of a call to Move; or
251/2 * The element it designates has been deleted.
252/2 {AI95-00302-03} The result of "=" or Has_Element is unspecified if it is
called with an invalid cursor parameter.{unspecified [partial]} Execution is
erroneous if any other subprogram declared in Containers.Vectors is called
with an invalid cursor parameter.{erroneous execution (cause) [partial]}
252.a/2 Discussion: The list above (combined with the bounded error cases)
is intended to be exhaustive. In other cases, a cursor value
continues to designate its original element. For instance, cursor
values survive the appending of new elements.
Implementation Requirements
253/2 {AI95-00302-03} No storage associated with a vector object shall be lost
upon assignment or scope exit.
254/2 {AI95-00302-03} The execution of an assignment_statement for a vector
shall have the effect of copying the elements from the source vector object to
the target vector object.
254.a/2 Implementation Note: An assignment of a Vector is a "deep" copy;
that is the elements are copied as well as the data structures. We
say "effect of" in order to allow the implementation to avoid
copying elements immediately if it wishes. For instance, an
implementation that avoided copying until one of the containers is
modified would be allowed.
Implementation Advice
255/2 {AI95-00302-03} Containers.Vectors should be implemented similarly to an
array. In particular, if the length of a vector is N, then
256/2 * the worst-case time complexity of Element should be O(log N);
256.a/2 Implementation Advice: The worst-case time complexity of Element
for Containers.Vector should be O(log N).
257 * the worst-case time complexity of Append with Count=1 when N is less
than the capacity of the vector should be O(log N); and
257.a/2 Implementation Advice: The worst-case time complexity of Append
with Count = 1 when N is less than the capacity for
Containers.Vector should be O(log N).
258/2 * the worst-case time complexity of Prepend with Count=1 and
Delete_First with Count=1 should be O(N log N).
258.a/2 Implementation Advice: The worst-case time complexity of Prepend
with Count = 1 and Delete_First with Count=1 for
Containers.Vectors should be O(N log N).
258.b/2 Reason: We do not mean to overly constrain implementation
strategies here. However, it is important for portability that the
performance of large containers has roughly the same factors on
different implementations. If a program is moved to an
implementation that takes O(N) time to access elements, that
program could be unusable when the vectors are large. We allow
O(log N) access because the proportionality constant and caching
effects are likely to be larger than the log factor, and we don't
want to discourage innovative implementations.
259/2 {AI95-00302-03} The worst-case time complexity of a call on procedure
Sort of an instance of Containers.Vectors.Generic_Sorting should be O(N**2),
and the average time complexity should be better than O(N**2).
259.a/2 Implementation Advice: The worst-case time complexity of a call on
procedure Sort of an instance of
Containers.Vectors.Generic_Sorting should be O(N**2), and the
average time complexity should be better than O(N**2).
259.b/2 Ramification: In other words, we're requiring the use of a better
than O(N**2) sorting algorithm, such as Quicksort. No bubble sorts
allowed!
260/2 {AI95-00302-03} Containers.Vectors.Generic_Sorting.Sort and
Containers.Vectors.Generic_Sorting.Merge should minimize copying of elements.
260.a/2 Implementation Advice: Containers.Vectors.Generic_Sorting.Sort and
Containers.Vectors.Generic_Sorting.Merge should minimize copying
of elements.
260.b/2 To be honest: We do not mean "absolutely minimize" here; we're not
intending to require a single copy for each element. Rather, we
want to suggest that the sorting algorithm chosen is one that does
not copy items unnecessarily. Bubble sort would not meet this
advice, for instance.
261/2 {AI95-00302-03} Move should not copy elements, and should minimize
copying of internal data structures.
261.a/2 Implementation Advice: Containers.Vectors.Move should not copy
elements, and should minimize copying of internal data structures.
261.b/2 Implementation Note: Usually that can be accomplished simply by
moving the pointer(s) to the internal data structures from the
Source vector to the Target vector.
262/2 {AI95-00302-03} If an exception is propagated from a vector operation,
no storage should be lost, nor any elements removed from a vector unless
specified by the operation.
262.a/2 Implementation Advice: If an exception is propagated from a vector
operation, no storage should be lost, nor any elements removed
from a vector unless specified by the operation.
262.b/2 Reason: This is important so that programs can recover from
errors. But we don't want to require heroic efforts, so we just
require documentation of cases where this can't be accomplished.
NOTES
263/2 42 All elements of a vector occupy locations in the internal array.
If a sparse container is required, a Hashed_Map should be used rather
than a vector.
264/2 43 If Index_Type'Base'First = Index_Type'First an instance of
Ada.Containers.Vectors will raise Constraint_Error. A value below
Index_Type'First is required so that an empty vector has a meaningful
value of Last_Index.
264.a/2 Discussion: This property is the main reason why only integer
types (as opposed to any discrete type) are allowed as the index
type of a vector. An enumeration or modular type would require a
subtype in order to meet this requirement.
Extensions to Ada 95
264.b/2 {AI95-00302-03} {extensions to Ada 95} The package
Containers.Vectors is new.
A.18.3 The Package Containers.Doubly_Linked_Lists
1/2 {AI95-00302-03} The language-defined generic package
Containers.Doubly_Linked_Lists provides private types List and Cursor, and a
set of operations for each type. A list container is optimized for insertion
and deletion at any position. {list container} {container (list)}
2/2 {AI95-00302-03} {node (of a list)} A doubly-linked list container object
manages a linked list of internal nodes, each of which contains an element and
pointers to the next (successor) and previous (predecessor) internal nodes. A
cursor designates a particular node within a list (and by extension the
element contained in that node). A cursor keeps designating the same node (and
element) as long as the node is part of the container, even if the node is
moved in the container.
3/2 {AI95-00302-03} The length of a list is the number of elements it
contains.{length (of a list container)}
Static Semantics
4/2 {AI95-00302-03} The generic library package Containers.Doubly_Linked_Lists
has the following declaration:
5/2 generic
type Element_Type is private;
with function "=" (Left, Right : Element_Type)
return Boolean is <>;
package Ada.Containers.Doubly_Linked_Lists is
pragma Preelaborate(Doubly_Linked_Lists);
6/2 type List is tagged private;
pragma Preelaborable_Initialization(List);
7/2 type Cursor is private;
pragma Preelaborable_Initialization(Cursor);
8/2 Empty_List : constant List;
9/2 No_Element : constant Cursor;
10/2 function "=" (Left, Right : List) return Boolean;
11/2 function Length (Container : List) return Count_Type;
12/2 function Is_Empty (Container : List) return Boolean;
13/2 procedure Clear (Container : in out List);
14/2 function Element (Position : Cursor)
return Element_Type;
15/2 procedure Replace_Element (Container : in out List;
Position : in Cursor;
New_Item : in Element_Type);
16/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Element : in Element_Type));
17/2 procedure Update_Element
(Container : in out List;
Position : in Cursor;
Process : not null access procedure
(Element : in out Element_Type));
18/2 procedure Move (Target : in out List;
Source : in out List);
19/2 procedure Insert (Container : in out List;
Before : in Cursor;
New_Item : in Element_Type;
Count : in Count_Type := 1);
20/2 procedure Insert (Container : in out List;
Before : in Cursor;
New_Item : in Element_Type;
Position : out Cursor;
Count : in Count_Type := 1);
21/2 procedure Insert (Container : in out List;
Before : in Cursor;
Position : out Cursor;
Count : in Count_Type := 1);
22/2 procedure Prepend (Container : in out List;
New_Item : in Element_Type;
Count : in Count_Type := 1);
23/2 procedure Append (Container : in out List;
New_Item : in Element_Type;
Count : in Count_Type := 1);
24/2 procedure Delete (Container : in out List;
Position : in out Cursor;
Count : in Count_Type := 1);
25/2 procedure Delete_First (Container : in out List;
Count : in Count_Type := 1);
26/2 procedure Delete_Last (Container : in out List;
Count : in Count_Type := 1);
27/2 procedure Reverse_Elements (Container : in out List);
28/2 procedure Swap (Container : in out List;
I, J : in Cursor);
29/2 procedure Swap_Links (Container : in out List;
I, J : in Cursor);
30/2 procedure Splice (Target : in out List;
Before : in Cursor;
Source : in out List);
31/2 procedure Splice (Target : in out List;
Before : in Cursor;
Source : in out List;
Position : in out Cursor);
32/2 procedure Splice (Container: in out List;
Before : in Cursor;
Position : in Cursor);
33/2 function First (Container : List) return Cursor;
34/2 function First_Element (Container : List)
return Element_Type;
35/2 function Last (Container : List) return Cursor;
36/2 function Last_Element (Container : List)
return Element_Type;
37/2 function Next (Position : Cursor) return Cursor;
38/2 function Previous (Position : Cursor) return Cursor;
39/2 procedure Next (Position : in out Cursor);
40/2 procedure Previous (Position : in out Cursor);
41/2 function Find (Container : List;
Item : Element_Type;
Position : Cursor := No_Element)
return Cursor;
42/2 function Reverse_Find (Container : List;
Item : Element_Type;
Position : Cursor := No_Element)
return Cursor;
43/2 function Contains (Container : List;
Item : Element_Type) return Boolean;
44/2 function Has_Element (Position : Cursor) return Boolean;
45/2 procedure Iterate
(Container : in List;
Process : not null access procedure (Position : in Cursor));
46/2 procedure Reverse_Iterate
(Container : in List;
Process : not null access procedure (Position : in Cursor));
47/2 generic
with function "<" (Left, Right : Element_Type)
return Boolean is <>;
package Generic_Sorting is
48/2 function Is_Sorted (Container : List) return Boolean;
49/2 procedure Sort (Container : in out List);
50/2 procedure Merge (Target : in out List;
Source : in out List);
51/2 end Generic_Sorting;
52/2 private
53/2 ... -- not specified by the language
54/2 end Ada.Containers.Doubly_Linked_Lists;
55/2 {AI95-00302-03} The actual function for the generic formal function "="
on Element_Type values is expected to define a reflexive and symmetric
relationship and return the same result value each time it is called with a
particular pair of values. If it behaves in some other manner, the functions
Find, Reverse_Find, and "=" on list values return an unspecified value. The
exact arguments and number of calls of this generic formal function by the
functions Find, Reverse_Find, and "=" on list values are
unspecified.{unspecified [partial]}
55.a/2 Ramification: If the actual function for "=" is not symmetric and
consistent, the result returned by the listed functions cannot be
predicted. The implementation is not required to protect against
"=" raising an exception, or returning random results, or any
other "bad" behavior. And it can call "=" in whatever manner makes
sense. But note that only the results of Find, Reverse_Find, and
List "=" are unspecified; other subprograms are not allowed to
break if "=" is bad (they aren't expected to use "=").
56/2 {AI95-00302-03} The type List is used to represent lists. The type List
needs finalization (see 7.6).
57/2 {AI95-00302-03} Empty_List represents the empty List object. It has a
length of 0. If an object of type List is not otherwise initialized, it is
initialized to the same value as Empty_List.
58/2 {AI95-00302-03} No_Element represents a cursor that designates no
element. If an object of type Cursor is not otherwise initialized, it is
initialized to the same value as No_Element.
59/2 {AI95-00302-03} The predefined "=" operator for type Cursor returns True
if both cursors are No_Element, or designate the same element in the same
container.
60/2 {AI95-00302-03} Execution of the default implementation of the Input,
Output, Read, or Write attribute of type Cursor raises Program_Error.
60.a/2 Reason: A cursor will probably be implemented in terms of one or
more access values, and the effects of streaming access values is
unspecified. Rather than letting the user stream junk by accident,
we mandate that streaming of cursors raise Program_Error by
default. The attributes can always be specified if there is a need
to support streaming.
61/2 {AI95-00302-03} [Some operations of this generic package have
access-to-subprogram parameters. To ensure such operations are well-defined,
they guard against certain actions by the designated subprogram. In
particular, some operations check for "tampering with cursors" of a container
because they depend on the set of elements of the container remaining
constant, and others check for "tampering with elements" of a container
because they depend on elements of the container not being replaced.]
62/2 {AI95-00302-03} {tamper with cursors (of a list)} A subprogram is said to
tamper with cursors of a list object L if:
63/2 * it inserts or deletes elements of L, that is, it calls the Insert,
Clear, Delete, or Delete_Last procedures with L as a parameter; or
63.a/2 To be honest: Operations which are defined to be equivalent to a
call on one of these operations also are included. Similarly,
operations which call one of these as part of their definition are
included.
64/2 * it reorders the elements of L, that is, it calls the Splice,
Swap_Links, or Reverse_Elements procedures or the Sort or Merge
procedures of an instance of Generic_Sorting with L as a parameter; or
65/2 * it finalizes L; or
66/2 * it calls the Move procedure with L as a parameter.
66.a/2 Reason: Swap copies elements rather than reordering them, so it
doesn't tamper with cursors.
67/2 {AI95-00302-03} {tamper with elements (of a list)} A subprogram is said
to tamper with elements of a list object L if:
68/2 * it tampers with cursors of L; or
69/2 * it replaces one or more elements of L, that is, it calls the
Replace_Element or Swap procedures with L as a parameter.
69.a/2 Reason: Complete replacement of an element can cause its memory to
be deallocated while another operation is holding onto a reference
to it. That can't be allowed. However, a simple modification of
(part of) an element is not a problem, so Update_Element does not
cause a problem.
70/2 function "=" (Left, Right : List) return Boolean;
71/2 {AI95-00302-03} If Left and Right denote the same list object,
then the function returns True. If Left and Right have different
lengths, then the function returns False. Otherwise, it compares
each element in Left to the corresponding element in Right using
the generic formal equality operator. If any such comparison
returns False, the function returns False; otherwise it returns
True. Any exception raised during evaluation of element equality
is propagated.
71.a/2 Implementation Note: This wording describes the canonical
semantics. However, the order and number of calls on the formal
equality function is unspecified for all of the operations that
use it in this package, so an implementation can call it as many
or as few times as it needs to get the correct answer.
Specifically, there is no requirement to call the formal equality
additional times once the answer has been determined.
72/2 function Length (Container : List) return Count_Type;
73/2 {AI95-00302-03} Returns the number of elements in Container.
74/2 function Is_Empty (Container : List) return Boolean;
75/2 {AI95-00302-03} Equivalent to Length (Container) = 0.
76/2 procedure Clear (Container : in out List);
77/2 {AI95-00302-03} Removes all the elements from Container.
78/2 function Element (Position : Cursor) return Element_Type;
79/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. Otherwise, Element returns the
element designated by Position.
80/2 procedure Replace_Element (Container : in out List;
Position : in Cursor;
New_Item : in Element_Type);
81/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated; if Position does not designate an
element in Container, then Program_Error is propagated. Otherwise
Replace_Element assigns the value New_Item to the element
designated by Position.
82/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Element : in Element_Type));
83/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. Otherwise, Query_Element calls
Process.all with the element designated by Position as the
argument. Program_Error is propagated if Process.all tampers with
the elements of Container. Any exception raised by Process.all is
propagated.
84/2 procedure Update_Element
(Container : in out List;
Position : in Cursor;
Process : not null access procedure (Element : in out Element_Type));
85/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated; if Position does not designate an
element in Container, then Program_Error is propagated. Otherwise
Update_Element calls Process.all with the element designated by
Position as the argument. Program_Error is propagated if
Process.all tampers with the elements of Container. Any exception
raised by Process.all is propagated.
86/2 If Element_Type is unconstrained and definite, then the actual
Element parameter of Process.all shall be unconstrained.
86.a/2 Ramification: This means that the elements cannot be directly
allocated from the heap; it must be possible to change the
discriminants of the element in place.
87/2 procedure Move (Target : in out List;
Source : in out List);
88/2 {AI95-00302-03} If Target denotes the same object as Source, then
Move has no effect. Otherwise, Move first calls Clear (Target).
Then, the nodes in Source are moved to Target (in the original
order). The length of Target is set to the length of Source, and
the length of Source is set to 0.
89/2 procedure Insert (Container : in out List;
Before : in Cursor;
New_Item : in Element_Type;
Count : in Count_Type := 1);
90/2 {AI95-00302-03} If Before is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. Otherwise, Insert inserts Count copies of New_Item
prior to the element designated by Before. If Before equals
No_Element, the new elements are inserted after the last node (if
any). Any exception raised during allocation of internal storage
is propagated, and Container is not modified.
90.a/2 Ramification: The check on Before checks that the cursor does not
belong to some other Container. This check implies that a
reference to the container is included in the cursor value. This
wording is not meant to require detection of dangling cursors;
such cursors are defined to be invalid, which means that execution
is erroneous, and any result is allowed (including not raising an
exception).
91/2 procedure Insert (Container : in out List;
Before : in Cursor;
New_Item : in Element_Type;
Position : out Cursor;
Count : in Count_Type := 1);
92/2 {AI95-00302-03} If Before is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. Otherwise, Insert allocates Count copies of New_Item,
and inserts them prior to the element designated by Before. If
Before equals No_Element, the new elements are inserted after the
last element (if any). Position designates the first
newly-inserted element. Any exception raised during allocation of
internal storage is propagated, and Container is not modified.
93/2 procedure Insert (Container : in out List;
Before : in Cursor;
Position : out Cursor;
Count : in Count_Type := 1);
94/2 {AI95-00302-03} If Before is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. Otherwise, Insert inserts Count new elements prior to
the element designated by Before. If Before equals No_Element, the
new elements are inserted after the last node (if any). The new
elements are initialized by default (see 3.3.1). Any exception
raised during allocation of internal storage is propagated, and
Container is not modified.
95/2 procedure Prepend (Container : in out List;
New_Item : in Element_Type;
Count : in Count_Type := 1);
96/2 {AI95-00302-03} Equivalent to Insert (Container, First
(Container), New_Item, Count).
97/2 procedure Append (Container : in out List;
New_Item : in Element_Type;
Count : in Count_Type := 1);
98/2 {AI95-00302-03} Equivalent to Insert (Container, No_Element,
New_Item, Count).
99/2 procedure Delete (Container : in out List;
Position : in out Cursor;
Count : in Count_Type := 1);
100/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. If Position does not designate an
element in Container, then Program_Error is propagated. Otherwise
Delete removes (from Container) Count elements starting at the
element designated by Position (or all of the elements starting at
Position if there are fewer than Count elements starting at
Position). Finally, Position is set to No_Element.
101/2 procedure Delete_First (Container : in out List;
Count : in Count_Type := 1);
102/2 {AI95-00302-03} Equivalent to Delete (Container, First
(Container), Count).
103/2 procedure Delete_Last (Container : in out List;
Count : in Count_Type := 1);
104/2 {AI95-00302-03} If Length (Container) <= Count then Delete_Last is
equivalent to Clear (Container). Otherwise it removes the last
Count nodes from Container.
105/2 procedure Reverse_Elements (Container : in out List);
106/2 {AI95-00302-03} Reorders the elements of Container in reverse
order.
106.a/2 Discussion: Unlike the similar routine for a vector, elements
should not be copied; rather, the nodes should be exchanged.
Cursors are expected to reference the same elements afterwards.
107/2 procedure Swap (Container : in out List;
I, J : in Cursor);
108/2 {AI95-00302-03} If either I or J is No_Element, then
Constraint_Error is propagated. If either I or J do not designate
an element in Container, then Program_Error is propagated.
Otherwise, Swap exchanges the values of the elements designated by
I and J.
108.a/2 Ramification: After a call to Swap, I designates the element value
previously designated by J, and J designates the element value
previously designated by I. The cursors do not become ambiguous
from this operation.
108.b/2 To be honest: The implementation is not required to actually copy
the elements if it can do the swap some other way. But it is
allowed to copy the elements if needed.
109/2 procedure Swap_Links (Container : in out List;
I, J : in Cursor);
110/2 {AI95-00302-03} If either I or J is No_Element, then
Constraint_Error is propagated. If either I or J do not designate
an element in Container, then Program_Error is propagated.
Otherwise, Swap_Links exchanges the nodes designated by I and J.
110.a/2 Ramification: Unlike Swap, this exchanges the nodes, not the
elements. No copying is performed. I and J designate the same
elements after this call as they did before it. This operation can
provide better performance than Swap if the element size is large.
111/2 procedure Splice (Target : in out List;
Before : in Cursor;
Source : in out List);
112/2 {AI95-00302-03} If Before is not No_Element, and does not
designate an element in Target, then Program_Error is propagated.
Otherwise, if Source denotes the same object as Target, the
operation has no effect. Otherwise, Splice reorders elements such
that they are removed from Source and moved to Target, immediately
prior to Before. If Before equals No_Element, the nodes of Source
are spliced after the last node of Target. The length of Target is
incremented by the number of nodes in Source, and the length of
Source is set to 0.
113/2 procedure Splice (Target : in out List;
Before : in Cursor;
Source : in out List;
Position : in out Cursor);
114/2 {AI95-00302-03} If Position is No_Element then Constraint_Error is
propagated. If Before does not equal No_Element, and does not
designate an element in Target, then Program_Error is propagated.
If Position does not equal No_Element, and does not designate a
node in Source, then Program_Error is propagated. If Source
denotes the same object as Target, then there is no effect if
Position equals Before, else the element designated by Position is
moved immediately prior to Before, or, if Before equals
No_Element, after the last element. In both cases, Position and
the length of Target are unchanged. Otherwise the element
designated by Position is removed from Source and moved to Target,
immediately prior to Before, or, if Before equals No_Element,
after the last element of Target. The length of Target is
incremented, the length of Source is decremented, and Position is
updated to represent an element in Target.
114.a/2 Ramification: If Source is the same as Target, and Position =
Before, or Next(Position} = Before, Splice has no effect, as the
element does not have to move to meet the postcondition.
115/2 procedure Splice (Container: in out List;
Before : in Cursor;
Position : in Cursor);
116/2 {AI95-00302-03} If Position is No_Element then Constraint_Error is
propagated. If Before does not equal No_Element, and does not
designate an element in Container, then Program_Error is
propagated. If Position does not equal No_Element, and does not
designate a node in Container, then Program_Error is propagated.
If Position equals Before there is no effect. Otherwise, the
element designated by Position is moved immediately prior to
Before, or, if Before equals No_Element, after the last element.
The length of Container is unchanged.
117/2 function First (Container : List) return Cursor;
118/2 {AI95-00302-03} If Container is empty, First returns the value
No_Element. Otherwise it returns a cursor that designates the
first node in Container.
119/2 function First_Element (Container : List) return Element_Type;
120/2 {AI95-00302-03} Equivalent to Element (First (Container)).
121/2 function Last (Container : List) return Cursor;
122/2 {AI95-00302-03} If Container is empty, Last returns the value
No_Element. Otherwise it returns a cursor that designates the last
node in Container.
123/2 function Last_Element (Container : List) return Element_Type;
124/2 {AI95-00302-03} Equivalent to Element (Last (Container)).
125/2 function Next (Position : Cursor) return Cursor;
126/2 {AI95-00302-03} If Position equals No_Element or designates the
last element of the container, then Next returns the value
No_Element. Otherwise, it returns a cursor that designates the
successor of the element designated by Position.
127/2 function Previous (Position : Cursor) return Cursor;
128/2 {AI95-00302-03} If Position equals No_Element or designates the
first element of the container, then Previous returns the value
No_Element. Otherwise, it returns a cursor that designates the
predecessor of the element designated by Position.
129/2 procedure Next (Position : in out Cursor);
130/2 {AI95-00302-03} Equivalent to Position := Next (Position).
131/2 procedure Previous (Position : in out Cursor);
132/2 {AI95-00302-03} Equivalent to Position := Previous (Position).
133/2 function Find (Container : List;
Item : Element_Type;
Position : Cursor := No_Element)
return Cursor;
134/2 {AI95-00302-03} If Position is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. Find searches the elements of Container for an element
equal to Item (using the generic formal equality operator). The
search starts at the element designated by Position, or at the
first element if Position equals No_Element. It proceeds towards
Last (Container). If no equal element is found, then Find returns
No_Element. Otherwise, it returns a cursor designating the first
equal element encountered.
135/2 function Reverse_Find (Container : List;
Item : Element_Type;
Position : Cursor := No_Element)
return Cursor;
136/2 {AI95-00302-03} If Position is not No_Element, and does not
designate an element in Container, then Program_Error is
propagated. Find searches the elements of Container for an element
equal to Item (using the generic formal equality operator). The
search starts at the element designated by Position, or at the
last element if Position equals No_Element. It proceeds towards
First (Container). If no equal element is found, then Reverse_Find
returns No_Element. Otherwise, it returns a cursor designating the
first equal element encountered.
137/2 function Contains (Container : List;
Item : Element_Type) return Boolean;
138/2 {AI95-00302-03} Equivalent to Find (Container, Item) /= No_Element.
139/2 function Has_Element (Position : Cursor) return Boolean;
140/2 {AI95-00302-03} Returns True if Position designates an element,
and returns False otherwise.
140.a/2 To be honest: This function may not detect cursors that designate
deleted elements; such cursors are invalid (see below) and the
result of Has_Element for an invalid cursor is unspecified (but
not erroneous).
141/2 procedure Iterate
(Container : in List;
Process : not null access procedure (Position : in Cursor));
142/2 {AI95-00302-03} Iterate calls Process.all with a cursor that
designates each node in Container, starting with the first node
and moving the cursor as per the Next function. Program_Error is
propagated if Process.all tampers with the cursors of Container.
Any exception raised by Process.all is propagated.
142.a/2 Implementation Note: The purpose of the tamper with cursors check
is to prevent erroneous execution from the Position parameter of
Process.all becoming invalid. This check takes place when the
operations that tamper with the cursors of the container are
called. The check cannot be made later (say in the body of
Iterate), because that could cause the Position cursor to be
invalid and potentially cause execution to become erroneous --
defeating the purpose of the check.
142.b/2 See Iterate for vectors (A.18.2) for a suggested implementation of
the check.
143/2 procedure Reverse_Iterate
(Container : in List;
Process : not null access procedure (Position : in Cursor));
144/2 {AI95-00302-03} Iterates over the nodes in Container as per
Iterate, except that elements are traversed in reverse order,
starting with the last node and moving the cursor as per the
Previous function.
145/2 The actual function for the generic formal function "<" of
Generic_Sorting is expected to return the same value each time it is called
with a particular pair of element values. It should define a strict ordering
relationship, that is, be irreflexive, asymmetric, and transitive; it should
not modify Container. If the actual for "<" behaves in some other manner, the
behavior of the subprograms of Generic_Sorting are unspecified. How many times
the subprograms of Generic_Sorting call "<" is unspecified.{unspecified
[partial]}
146/2 function Is_Sorted (Container : List) return Boolean;
147/2 {AI95-00302-03} Returns True if the elements are sorted smallest
first as determined by the generic formal "<" operator; otherwise,
Is_Sorted returns False. Any exception raised during evaluation of
"<" is propagated.
148/2 procedure Sort (Container : in out List);
149/2 {AI95-00302-03} Reorders the nodes of Container such that the
elements are sorted smallest first as determined by the generic
formal "<" operator provided. The sort is stable. Any exception
raised during evaluation of "<" is propagated.
149.a/2 Ramification: Unlike array sorts, we do require stable sorts here.
That's because algorithms in the merge sort family (as described
by Knuth) can be both fast and stable. Such sorts use the extra
memory as offered by the links to provide better performance.
149.b/2 Note that list sorts never copy elements; it is the nodes, not the
elements, that are reordered.
150/2 procedure Merge (Target : in out List;
Source : in out List);
151/2 {AI95-00302-03} Merge removes elements from Source and inserts
them into Target; afterwards, Target contains the union of the
elements that were initially in Source and Target; Source is left
empty. If Target and Source are initially sorted smallest first,
then Target is ordered smallest first as determined by the generic
formal "<" operator; otherwise, the order of elements in Target is
unspecified. Any exception raised during evaluation of "<" is
propagated.
151.a/2 Ramification: It is a bounded error if either of the lists is
unsorted, see below. The bounded error can be recovered by sorting
Target after the merge call, or the lists can be pretested with
Is_Sorted.
Bounded (Run-Time) Errors
152/2 {AI95-00302-03} {bounded error (cause) [partial]} Calling Merge in an
instance of Generic_Sorting with either Source or Target not ordered smallest
first using the provided generic formal "<" operator is a bounded error.
Either Program_Error is raised after Target is updated as described for Merge,
or the operation works as defined.
Erroneous Execution
153/2 {AI95-00302-03} A Cursor value is invalid if any of the following have
occurred since it was created:{invalid cursor (of a list container)}
{cursor (invalid) [partial]}
154/2 * The list that contains the element it designates has been finalized;
155/2 * The list that contains the element it designates has been used as
the Source or Target of a call to Move; or
156/2 * The element it designates has been deleted.
157/2 {AI95-00302-03} The result of "=" or Has_Element is unspecified if it is
called with an invalid cursor parameter. Execution is erroneous if any other
subprogram declared in Containers.Doubly_Linked_Lists is called with an
invalid cursor parameter. {unspecified [partial]}
{erroneous execution (cause) [partial]}
157.a/2 Discussion: The list above is intended to be exhaustive. In other
cases, a cursor value continues to designate its original element.
For instance, cursor values survive the insertion and deletion of
other nodes.
157.b/2 While it is possible to check for these cases, in many cases the
overhead necessary to make the check is substantial in time or
space. Implementations are encouraged to check for as many of
these cases as possible and raise Program_Error if detected.
Implementation Requirements
158/2 {AI95-00302-03} No storage associated with a doubly-linked List object
shall be lost upon assignment or scope exit.
159/2 {AI95-00302-03} The execution of an assignment_statement for a list
shall have the effect of copying the elements from the source list object to
the target list object.
159.a/2 Implementation Note: An assignment of a List is a "deep" copy;
that is the elements are copied as well as the data structures. We
say "effect of" in order to allow the implementation to avoid
copying elements immediately if it wishes. For instance, an
implementation that avoided copying until one of the containers is
modified would be allowed.
Implementation Advice
160/2 {AI95-00302-03} Containers.Doubly_Linked_Lists should be implemented
similarly to a linked list. In particular, if N is the length of a list, then
the worst-case time complexity of Element, Insert with Count=1, and Delete
with Count=1 should be O(log N).
160.a/2 Implementation Advice: The worst-case time complexity of Element,
Insert with Count=1, and Delete with Count=1 for
Containers.Doubly_Linked_Lists should be O(log N).
160.b/2 Reason: We do not mean to overly constrain implementation
strategies here. However, it is important for portability that the
performance of large containers has roughly the same factors on
different implementations. If a program is moved to an
implementation that takes O(N) time to access elements, that
program could be unusable when the lists are large. We allow O(log
N) access because the proportionality constant and caching effects
are likely to be larger than the log factor, and we don't want to
discourage innovative implementations.
161/2 {AI95-00302-03} The worst-case time complexity of a call on procedure
Sort of an instance of Containers.Doubly_Linked_Lists.Generic_Sorting should
be O(N**2), and the average time complexity should be better than O(N**2).
161.a/2 Implementation Advice: a call on procedure Sort of an instance of
Containers.Doubly_Linked_Lists.Generic_Sorting should have an
average time complexity better than O(N**2) and worst case no
worse than O(N**2).
161.b/2 Ramification: In other words, we're requiring the use of a better
than O(N**2) sorting algorithm, such as Quicksort. No bubble sorts
allowed!
162/2 {AI95-00302-03} Move should not copy elements, and should minimize
copying of internal data structures.
162.a/2 Implementation Advice: Containers.Doubly_Link_Lists.Move should
not copy elements, and should minimize copying of internal data
structures.
162.b/2 Implementation Note: Usually that can be accomplished simply by
moving the pointer(s) to the internal data structures from the
Source container to the Target container.
163/2 {AI95-00302-03} If an exception is propagated from a list operation, no
storage should be lost, nor any elements removed from a list unless specified
by the operation.
163.a/2 Implementation Advice: If an exception is propagated from a list
operation, no storage should be lost, nor any elements removed
from a list unless specified by the operation.
163.b/2 Reason: This is important so that programs can recover from
errors. But we don't want to require heroic efforts, so we just
require documentation of cases where this can't be accomplished.
NOTES
164/2 44 {AI95-00302-03} Sorting a list never copies elements, and is a
stable sort (equal elements remain in the original order). This is
different than sorting an array or vector, which may need to copy
elements, and is probably not a stable sort.
Extensions to Ada 95
164.a/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Doubly_Linked_Lists is new.
A.18.4 Maps
1/2 {AI95-00302-03} The language-defined generic packages
Containers.Hashed_Maps and Containers.Ordered_Maps provide private types Map
and Cursor, and a set of operations for each type. A map container allows an
arbitrary type to be used as a key to find the element associated with that
key. A hashed map uses a hash function to organize the keys, while an ordered
map orders the keys per a specified relation. {map container}
{container (map)}
2/2 {AI95-00302-03} This section describes the declarations that are common to
both kinds of maps. See A.18.5 for a description of the semantics specific to
Containers.Hashed_Maps and A.18.6 for a description of the semantics specific
to Containers.Ordered_Maps.
Static Semantics
3/2 {AI95-00302-03} The actual function for the generic formal function "=" on
Element_Type values is expected to define a reflexive and symmetric
relationship and return the same result value each time it is called with a
particular pair of values. If it behaves in some other manner, the function
"=" on map values returns an unspecified value. The exact arguments and number
of calls of this generic formal function by the function "=" on map values are
unspecified.{unspecified [partial]}
3.a/2 Ramification: If the actual function for "=" is not symmetric and
consistent, the result returned by "=" for Map objects cannot be
predicted. The implementation is not required to protect against
"=" raising an exception, or returning random results, or any
other "bad" behavior. And it can call "=" in whatever manner makes
sense. But note that only the result of "=" for Map objects is
unspecified; other subprograms are not allowed to break if "=" is
bad (they aren't expected to use "=").
4/2 {AI95-00302-03} The type Map is used to represent maps. The type Map needs
finalization (see 7.6).
5/2 {AI95-00302-03} {node (of a map)} A map contains pairs of keys and
elements, called nodes. Map cursors designate nodes, but also can be thought
of as designating an element (the element contained in the node) for
consistency with the other containers. There exists an equivalence relation on
keys, whose definition is different for hashed maps and ordered maps. A map
never contains two or more nodes with equivalent keys. The length of a map is
the number of nodes it contains.{length (of a map)}
6/2 {AI95-00302-03} {first node (of a map)} {last node (of a map)}
{successor node (of a map)} Each nonempty map has two particular nodes called
the first node and the last node (which may be the same). Each node except for
the last node has a successor node. If there are no other intervening
operations, starting with the first node and repeatedly going to the successor
node will visit each node in the map exactly once until the last node is
reached. The exact definition of these terms is different for hashed maps and
ordered maps.
7/2 {AI95-00302-03} [Some operations of these generic packages have
access-to-subprogram parameters. To ensure such operations are well-defined,
they guard against certain actions by the designated subprogram. In
particular, some operations check for "tampering with cursors" of a container
because they depend on the set of elements of the container remaining
constant, and others check for "tampering with elements" of a container
because they depend on elements of the container not being replaced.]
8/2 {AI95-00302-03} {tamper with cursors (of a map)} A subprogram is said to
tamper with cursors of a map object M if:
9/2 * it inserts or deletes elements of M, that is, it calls the Insert,
Include, Clear, Delete, or Exclude procedures with M as a parameter; or
9.a/2 To be honest: Operations which are defined to be equivalent to a
call on one of these operations also are included. Similarly,
operations which call one of these as part of their definition are
included.
10/2 * it finalizes M; or
11/2 * it calls the Move procedure with M as a parameter; or
12/2 * it calls one of the operations defined to tamper with the cursors of
M.
12.a/2 Ramification: Replace only modifies a key and element rather than
rehashing, so it does not tamper with cursors.
13/2 {AI95-00302-03} {tamper with elements (of a map)} A subprogram is said to
tamper with elements of a map object M if:
14/2 * it tampers with cursors of M; or
15/2 * it replaces one or more elements of M, that is, it calls the Replace
or Replace_Element procedures with M as a parameter.
15.a/2 Reason: Complete replacement of an element can cause its memory to
be deallocated while another operation is holding onto a reference
to it. That can't be allowed. However, a simple modification of
(part of) an element is not a problem, so Update_Element does not
cause a problem.
16/2 {AI95-00302-03} Empty_Map represents the empty Map object. It has a
length of 0. If an object of type Map is not otherwise initialized, it is
initialized to the same value as Empty_Map.
17/2 {AI95-00302-03} No_Element represents a cursor that designates no node.
If an object of type Cursor is not otherwise initialized, it is initialized to
the same value as No_Element.
18/2 {AI95-00302-03} The predefined "=" operator for type Cursor returns True
if both cursors are No_Element, or designate the same element in the same
container.
19/2 {AI95-00302-03} Execution of the default implementation of the Input,
Output, Read, or Write attribute of type Cursor raises Program_Error.
19.a/2 Reason: A cursor will probably be implemented in terms of one or
more access values, and the effects of streaming access values is
unspecified. Rather than letting the user stream junk by accident,
we mandate that streaming of cursors raise Program_Error by
default. The attributes can always be specified if there is a need
to support streaming.
20/2 function "=" (Left, Right : Map) return Boolean;
21/2 {AI95-00302-03} If Left and Right denote the same map object, then
the function returns True. If Left and Right have different
lengths, then the function returns False. Otherwise, for each key
K in Left, the function returns False if:
22/2 * a key equivalent to K is not present in Right; or
23/2 * the element associated with K in Left is not equal to the
element associated with K in Right (using the generic formal
equality operator for elements).
24/2 If the function has not returned a result after checking all of
the keys, it returns True. Any exception raised during evaluation
of key equivalence or element equality is propagated.
24.a/2 Implementation Note: This wording describes the canonical
semantics. However, the order and number of calls on the formal
equality function is unspecified for all of the operations that
use it in this package, so an implementation can call it as many
or as few times as it needs to get the correct answer.
Specifically, there is no requirement to call the formal equality
additional times once the answer has been determined.
25/2 function Length (Container : Map) return Count_Type;
26/2 {AI95-00302-03} Returns the number of nodes in Container.
27/2 function Is_Empty (Container : Map) return Boolean;
28/2 {AI95-00302-03} Equivalent to Length (Container) = 0.
29/2 procedure Clear (Container : in out Map);
30/2 {AI95-00302-03} Removes all the nodes from Container.
31/2 function Key (Position : Cursor) return Key_Type;
32/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. Otherwise, Key returns the key
component of the node designated by Position.
33/2 function Element (Position : Cursor) return Element_Type;
34/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. Otherwise, Element returns the
element component of the node designated by Position.
35/2 procedure Replace_Element (Container : in out Map;
Position : in Cursor;
New_Item : in Element_Type);
36/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated; if Position does not designate an
element in Container, then Program_Error is propagated. Otherwise
Replace_Element assigns New_Item to the element of the node
designated by Position.
37/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Key : in Key_Type;
Element : in Element_Type));
38/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. Otherwise, Query_Element calls
Process.all with the key and element from the node designated by
Position as the arguments. Program_Error is propagated if
Process.all tampers with the elements of Container. Any exception
raised by Process.all is propagated.
39/2 procedure Update_Element
(Container : in out Map;
Position : in Cursor;
Process : not null access procedure (Key : in Key_Type;
Element : in out Element_Type));
40/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated; if Position does not designate an
element in Container, then Program_Error is propagated. Otherwise
Update_Element calls Process.all with the key and element from the
node designated by Position as the arguments. Program_Error is
propagated if Process.all tampers with the elements of Container.
Any exception raised by Process.all is propagated.
41/2 If Element_Type is unconstrained and definite, then the actual
Element parameter of Process.all shall be unconstrained.
41.a/2 Ramification: This means that the elements cannot be directly
allocated from the heap; it must be possible to change the
discriminants of the element in place.
42/2 procedure Move (Target : in out Map;
Source : in out Map);
43/2 {AI95-00302-03} If Target denotes the same object as Source, then
Move has no effect. Otherwise, Move first calls Clear (Target).
Then, each node from Source is removed from Source and inserted
into Target. The length of Source is 0 after a successful call to
Move.
44/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type;
Position : out Cursor;
Inserted : out Boolean);
45/2 {AI95-00302-03} Insert checks if a node with a key equivalent to
Key is already present in Container. If a match is found, Inserted
is set to False and Position designates the element with the
matching key. Otherwise, Insert allocates a new node, initializes
it to Key and New_Item, and adds it to Container; Inserted is set
to True and Position designates the newly-inserted node. Any
exception raised during allocation is propagated and Container is
not modified.
46/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
Position : out Cursor;
Inserted : out Boolean);
47/2 {AI95-00302-03} Insert inserts Key into Container as per the
five-parameter Insert, with the difference that an element
initialized by default (see 3.3.1) is inserted.
48/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type);
49/2 {AI95-00302-03} Insert inserts Key and New_Item into Container as
per the five-parameter Insert, with the difference that if a node
with a key equivalent to Key is already in the map, then
Constraint_Error is propagated.
49.a/2 Ramification: This is equivalent to:
49.b/2 declare
Inserted : Boolean; C : Cursor;
begin
Insert (Container, Key, New_Item, C, Inserted);
if not Inserted then
raise Constraint_Error;
end if;
end;
49.c/2 but doesn't require the hassle of out parameters.
50/2 procedure Include (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type);
51/2 {AI95-00302-03} Include inserts Key and New_Item into Container as
per the five-parameter Insert, with the difference that if a node
with a key equivalent to Key is already in the map, then this
operation assigns Key and New_Item to the matching node. Any
exception raised during assignment is propagated.
51.a/2 Ramification: This is equivalent to:
51.b/2 declare
C : Cursor := Find (Container, Key);
begin
if C = No_Element then
Insert (Container, Key, New_Item);
else
Replace (Container, Key, New_Item);
end if;
end;
51.c/2 but this avoids doing the search twice.
52/2 procedure Replace (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type);
53/2 {AI95-00302-03} Replace checks if a node with a key equivalent to
Key is present in Container. If a match is found, Replace assigns
Key and New_Item to the matching node; otherwise, Constraint_Error
is propagated.
53.a/2 Discussion: We update the key as well as the element, as the key
might include additional information that does not participate in
equivalence. If only the element needs to be updated, use
Replace_Element (Find (Container, Key), New_Element).
54/2 procedure Exclude (Container : in out Map;
Key : in Key_Type);
55/2 {AI95-00302-03} Exclude checks if a node with a key equivalent to
Key is present in Container. If a match is found, Exclude removes
the node from the map.
55.a/2 Ramification: Exclude should work on an empty map; nothing happens
in that case.
56/2 procedure Delete (Container : in out Map;
Key : in Key_Type);
57/2 {AI95-00302-03} Delete checks if a node with a key equivalent to
Key is present in Container. If a match is found, Delete removes
the node from the map; otherwise, Constraint_Error is propagated.
58/2 procedure Delete (Container : in out Map;
Position : in out Cursor);
59/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. If Position does not designate an
element in Container, then Program_Error is propagated. Otherwise,
Delete removes the node designated by Position from the map.
Position is set to No_Element on return.
59.a/2 Ramification: The check on Position checks that the cursor does
not belong to some other map. This check implies that a reference
to the map is included in the cursor value. This wording is not
meant to require detection of dangling cursors; such cursors are
defined to be invalid, which means that execution is erroneous,
and any result is allowed (including not raising an exception).
60/2 function First (Container : Map) return Cursor;
61/2 {AI95-00302-03} If Length (Container) = 0, then First returns
No_Element. Otherwise, First returns a cursor that designates the
first node in Container.
62/2 function Next (Position : Cursor) return Cursor;
63/2 {AI95-00302-03} Returns a cursor that designates the successor of
the node designated by Position. If Position designates the last
node, then No_Element is returned. If Position equals No_Element,
then No_Element is returned.
64/2 procedure Next (Position : in out Cursor);
65/2 {AI95-00302-03} Equivalent to Position := Next (Position).
66/2 function Find (Container : Map;
Key : Key_Type) return Cursor;
67/2 {AI95-00302-03} If Length (Container) equals 0, then Find returns
No_Element. Otherwise, Find checks if a node with a key equivalent
to Key is present in Container. If a match is found, a cursor
designating the matching node is returned; otherwise, No_Element
is returned.
68/2 function Element (Container : Map;
Key : Key_Type) return Element_Type;
69/2 {AI95-00302-03} Equivalent to Element (Find (Container, Key)).
70/2 function Contains (Container : Map;
Key : Key_Type) return Boolean;
71/2 {AI95-00302-03} Equivalent to Find (Container, Key) /= No_Element.
72/2 function Has_Element (Position : Cursor) return Boolean;
73/2 {AI95-00302-03} Returns True if Position designates a node, and
returns False otherwise.
73.a/2 To be honest: This function may not detect cursors that designate
deleted elements; such cursors are invalid (see below); the result
of Has_Element for invalid cursors is unspecified (but not
erroneous).
74/2 procedure Iterate
(Container : in Map;
Process : not null access procedure (Position : in Cursor));
75/2 {AI95-00302-03} Iterate calls Process.all with a cursor that
designates each node in Container, starting with the first node
and moving the cursor according to the successor relation.
Program_Error is propagated if Process.all tampers with the
cursors of Container. Any exception raised by Process.all is
propagated.
75.a/2 Implementation Note: The "tamper with cursors" check takes place
when the operations that insert or delete elements, and so on, are
called.
75.b/2 See Iterate for vectors (A.18.2) for a suggested implementation of
the check.
Erroneous Execution
76/2 {AI95-00302-03} A Cursor value is invalid if any of the following have
occurred since it was created:{invalid cursor (of a map)} {cursor (invalid)
[partial]}
77/2 * The map that contains the node it designates has been finalized;
78/2 * The map that contains the node it designates has been used as the
Source or Target of a call to Move; or
79/2 * The node it designates has been deleted from the map.
80/2 The result of "=" or Has_Element is unspecified if these functions are
called with an invalid cursor parameter.{unspecified [partial]} Execution is
erroneous if any other subprogram declared in Containers.Hashed_Maps or
Containers.Ordered_Maps is called with an invalid cursor
parameter.{erroneous execution (cause) [partial]}
80.a/2 Discussion: The list above is intended to be exhaustive. In other
cases, a cursor value continues to designate its original element.
For instance, cursor values survive the insertion and deletion of
other nodes.
80.b/2 While it is possible to check for these cases, in many cases the
overhead necessary to make the check is substantial in time or
space. Implementations are encouraged to check for as many of
these cases as possible and raise Program_Error if detected.
Implementation Requirements
81/2 {AI95-00302-03} No storage associated with a Map object shall be lost
upon assignment or scope exit.
82/2 {AI95-00302-03} The execution of an assignment_statement for a map shall
have the effect of copying the elements from the source map object to the
target map object.
82.a/2 Implementation Note: An assignment of a Map is a "deep" copy; that
is the elements are copied as well as the data structures. We say
"effect of" in order to allow the implementation to avoid copying
elements immediately if it wishes. For instance, an implementation
that avoided copying until one of the containers is modified would
be allowed.
Implementation Advice
83/2 {AI95-00302-03} Move should not copy elements, and should minimize
copying of internal data structures.
83.a/2 Implementation Advice: Move for a map should not copy elements,
and should minimize copying of internal data structures.
83.b/2 Implementation Note: Usually that can be accomplished simply by
moving the pointer(s) to the internal data structures from the
Source container to the Target container.
84/2 {AI95-00302-03} If an exception is propagated from a map operation, no
storage should be lost, nor any elements removed from a map unless specified
by the operation.
84.a/2 Implementation Advice: If an exception is propagated from a map
operation, no storage should be lost, nor any elements removed
from a map unless specified by the operation.
84.b/2 Reason: This is important so that programs can recover from
errors. But we don't want to require heroic efforts, so we just
require documentation of cases where this can't be accomplished.
Wording Changes from Ada 95
84.c/2 {AI95-00302-03} This description of maps is new; the extensions
are documented with the specific packages.
A.18.5 The Package Containers.Hashed_Maps
Static Semantics
1/2 {AI95-00302-03} The generic library package Containers.Hashed_Maps has the
following declaration:
2/2 generic
type Key_Type is private;
type Element_Type is private;
with function Hash (Key : Key_Type) return Hash_Type;
with function Equivalent_Keys (Left, Right : Key_Type)
return Boolean;
with function "=" (Left, Right : Element_Type)
return Boolean is <>;
package Ada.Containers.Hashed_Maps is
pragma Preelaborate(Hashed_Maps);
3/2 type Map is tagged private;
pragma Preelaborable_Initialization(Map);
4/2 type Cursor is private;
pragma Preelaborable_Initialization(Cursor);
5/2 Empty_Map : constant Map;
6/2 No_Element : constant Cursor;
7/2 function "=" (Left, Right : Map) return Boolean;
8/2 function Capacity (Container : Map) return Count_Type;
9/2 procedure Reserve_Capacity (Container : in out Map;
Capacity : in Count_Type);
10/2 function Length (Container : Map) return Count_Type;
11/2 function Is_Empty (Container : Map) return Boolean;
12/2 procedure Clear (Container : in out Map);
13/2 function Key (Position : Cursor) return Key_Type;
14/2 function Element (Position : Cursor) return Element_Type;
15/2 procedure Replace_Element (Container : in out Map;
Position : in Cursor;
New_Item : in Element_Type);
16/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Key : in Key_Type;
Element : in Element_Type));
17/2 procedure Update_Element
(Container : in out Map;
Position : in Cursor;
Process : not null access procedure
(Key : in Key_Type;
Element : in out Element_Type));
18/2 procedure Move (Target : in out Map;
Source : in out Map);
19/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type;
Position : out Cursor;
Inserted : out Boolean);
20/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
Position : out Cursor;
Inserted : out Boolean);
21/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type);
22/2 procedure Include (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type);
23/2 procedure Replace (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type);
24/2 procedure Exclude (Container : in out Map;
Key : in Key_Type);
25/2 procedure Delete (Container : in out Map;
Key : in Key_Type);
26/2 procedure Delete (Container : in out Map;
Position : in out Cursor);
27/2 function First (Container : Map)
return Cursor;
28/2 function Next (Position : Cursor) return Cursor;
29/2 procedure Next (Position : in out Cursor);
30/2 function Find (Container : Map;
Key : Key_Type)
return Cursor;
31/2 function Element (Container : Map;
Key : Key_Type)
return Element_Type;
32/2 function Contains (Container : Map;
Key : Key_Type) return Boolean;
33/2 function Has_Element (Position : Cursor) return Boolean;
34/2 function Equivalent_Keys (Left, Right : Cursor)
return Boolean;
35/2 function Equivalent_Keys (Left : Cursor;
Right : Key_Type)
return Boolean;
36/2 function Equivalent_Keys (Left : Key_Type;
Right : Cursor)
return Boolean;
37/2 procedure Iterate
(Container : in Map;
Process : not null access procedure (Position : in Cursor));
38/2 private
39/2 ... -- not specified by the language
40/2 end Ada.Containers.Hashed_Maps;
41/2 {AI95-00302-03} An object of type Map contains an expandable hash table,
which is used to provide direct access to nodes. The capacity of an object of
type Map is the maximum number of nodes that can be inserted into the hash
table prior to it being automatically expanded.{capacity (of a hashed map)}
41.a/2 Implementation Note: The expected implementation for a Map uses a
hash table which is grown when it is too small, with linked lists
hanging off of each bucket. Note that in that implementation a
cursor needs a back pointer to the Map object to implement
iteration; that could either be in the nodes, or in the cursor
object. To provide an average O(1) access time, capacity would
typically equal the number of buckets in such an implementation,
so that the average bucket linked list length would be no more
than 1.0.
41.b/2 There is no defined relationship between elements in a hashed map.
Typically, iteration will return elements in the order that they
are hashed in.
42/2 {AI95-00302-03} {equivalent key (of a hashed map)} Two keys K1 and K2 are
defined to be equivalent if Equivalent_Keys (K1, K2) returns True.
43/2 {AI95-00302-03} The actual function for the generic formal function Hash
is expected to return the same value each time it is called with a particular
key value. For any two equivalent key values, the actual for Hash is expected
to return the same value. If the actual for Hash behaves in some other manner,
the behavior of this package is unspecified. Which subprograms of this package
call Hash, and how many times they call it, is unspecified.{unspecified
[partial]}
43.a/2 Implementation Note: The implementation is not required to protect
against Hash raising an exception, or returning random numbers, or
any other "bad" behavior. It's not practical to do so, and a
broken Hash function makes the container unusable.
43.b/2 The implementation can call Hash whenever it is needed; we don't
want to specify how often that happens. The result must remain the
same (this is logically a pure function), or the behavior is
unspecified.
44/2 {AI95-00302-03} The actual function for the generic formal function
Equivalent_Keys on Key_Type values is expected to return the same value each
time it is called with a particular pair of key values. It should define an
equivalence relationship, that is, be reflexive, symmetric, and transitive. If
the actual for Equivalent_Keys behaves in some other manner, the behavior of
this package is unspecified. Which subprograms of this package call
Equivalent_Keys, and how many times they call it, is
unspecified.{unspecified [partial]}
44.a/2 Implementation Note: As with Hash, the implementation is not
required to protect against Equivalent_Keys raising an exception
or returning random results. Similarly, the implementation can
call this operation whenever it is needed. The result must remain
the same (this is a logically pure function), or the behavior is
unspecified.
45/2 {AI95-00302-03} If the value of a key stored in a node of a map is
changed other than by an operation in this package such that at least one of
Hash or Equivalent_Keys give different results, the behavior of this package
is unspecified.{unspecified [partial]}
45.a/2 Implementation Note: The implementation is not required to protect
against changes to key values other than via the operations
declared in the Hashed_Maps package.
45.b/2 To see how this could happen, imagine an instance of Hashed_Maps
where the key type is an access-to-variable type and Hash returns
a value derived from the components of the designated object.
Then, any operation that has a key value could modify those
components and change the hash value:
45.c/2 Key (Map).Some_Component := New_Value;
45.d/2 This is really a design error on the part of the user of the map;
it shouldn't be possible to modify keys stored in a map. But we
can't prevent this error anymore than we can prevent someone
passing as Hash a random number generator.
46/2 {AI95-00302-03} {first node (of a hashed map)}
{last node (of a hashed map)} {successor node (of a hashed map)} Which nodes
are the first node and the last node of a map, and which node is the successor
of a given node, are unspecified, other than the general semantics described
in A.18.4.{unspecified [partial]}
46.a/2 Implementation Note: Typically the first node will be the first
node in the first bucket, the last node will be the last node in
the last bucket, and the successor will be obtained by following
the collision list, and going to the next bucket at the end of
each bucket.
47/2 function Capacity (Container : Map) return Count_Type;
48/2 {AI95-00302-03} Returns the capacity of Container.
49/2 procedure Reserve_Capacity (Container : in out Map;
Capacity : in Count_Type);
50/2 {AI95-00302-03} Reserve_Capacity allocates a new hash table such
that the length of the resulting map can become at least the value
Capacity without requiring an additional call to Reserve_Capacity,
and is large enough to hold the current length of Container.
Reserve_Capacity then rehashes the nodes in Container onto the new
hash table. It replaces the old hash table with the new hash
table, and then deallocates the old hash table. Any exception
raised during allocation is propagated and Container is not
modified.
51/2 Reserve_Capacity tampers with the cursors of Container.
51.a/2 Implementation Note: This routine is used to preallocate the
internal hash table to the specified capacity such that future
Inserts do not require expansion of the hash table. Therefore, the
implementation should allocate the needed memory to make that true
at this point, even though the visible semantics could be
preserved by waiting until enough elements are inserted.
51.b/2 While Reserve_Capacity can be used to reduce the capacity of a
map, we do not specify whether an implementation actually supports
reduction of the capacity. Since the actual capacity can be
anything greater than or equal to Count, an implementation never
has to reduce the capacity.
51.c/2 Reserve_Capacity tampers with the cursors, as rehashing probably
will change the order that elements are stored in the map.
52/2 procedure Clear (Container : in out Map);
53/2 {AI95-00302-03} In addition to the semantics described in A.18.4,
Clear does not affect the capacity of Container.
53.a/2 Implementation Note: In:
53.b/2 procedure Move (Target : in out Map;
Source : in out Map);
53.c/2 The intended implementation is that the internal hash table of
Target is first deallocated; then the internal hash table is
removed from Source and moved to Target.
54/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type;
Position : out Cursor;
Inserted : out Boolean);
55/2 {AI95-00302-03} In addition to the semantics described in A.18.4,
if Length (Container) equals Capacity (Container), then Insert
first calls Reserve_Capacity to increase the capacity of Container
to some larger value.
55.a/2 Implementation Note: Insert should only compare keys that hash to
the same bucket in the hash table.
55.b/2 We specify when Reserve_Capacity is called to bound the overhead
of capacity expansion operations (which are potentially
expensive). Moreover, expansion can be predicted by comparing
Capacity(Map) to Length(Map). Since we don't specify by how much
the hash table is expanded, this only can be used to predict the
next expansion, not later ones.
55.c/2 Implementation Note: In:
55.d/2 procedure Exclude (Container : in out Map;
Key : in Key_Type);
55.e/2 Exclude should only compare keys that hash to the same bucket in
the hash table.
55.f/2 Implementation Note: In:
55.g/2 procedure Delete (Container : in out Map;
Key : in Key_Type);
55.h/2 Delete should only compare keys that hash to the same bucket in
the hash table. The node containing the element may be deallocated
now, or it may be saved and reused later.
55.i/2 Implementation Note: In:
55.j/2 function First (Container : Map) return Cursor;
55.k/2 In a typical implementation, this will be the first node in the
lowest numbered hash bucket that contains a node.
55.l/2 Implementation Note: In:
55.m/2 function Next (Position : Cursor) return Cursor;
55.n/2 In a typical implementation, this will return the next node in a
bucket; if Position is the last node in a bucket, this will return
the first node in the next non-empty bucket.
55.o/2 A typical implementation will need to a keep a pointer at the map
container in the cursor in order to implement this function.
55.p/2 Implementation Note: In:
55.q/2 function Find (Container : Map;
Key : Key_Type) return Cursor;
55.r/2 Find should only compare keys that hash to the same bucket in the
hash table.
56/2 function Equivalent_Keys (Left, Right : Cursor)
return Boolean;
57/2 {AI95-00302-03} Equivalent to Equivalent_Keys (Key (Left), Key
(Right)).
58/2 function Equivalent_Keys (Left : Cursor;
Right : Key_Type) return Boolean;
59/2 {AI95-00302-03} Equivalent to Equivalent_Keys (Key (Left), Right).
60/2 function Equivalent_Keys (Left : Key_Type;
Right : Cursor) return Boolean;
61/2 {AI95-00302-03} Equivalent to Equivalent_Keys (Left, Key (Right)).
Implementation Advice
62/2 {AI95-00302-03} If N is the length of a map, the average time complexity
of the subprograms Element, Insert, Include, Replace, Delete, Exclude and Find
that take a key parameter should be O(log N). The average time complexity of
the subprograms that take a cursor parameter should be O(1). The average time
complexity of Reserve_Capacity should be O(N).
62.a/2 Implementation Advice: The average time complexity of Element,
Insert, Include, Replace, Delete, Exclude and Find operations that
take a key parameter for Containers.Hashed_Maps should be O(log
N). The average time complexity of the subprograms of
Containers.Hashed_Maps that take a cursor parameter should be O(1).
62.b/2 Reason: We do not mean to overly constrain implementation
strategies here. However, it is important for portability that the
performance of large containers has roughly the same factors on
different implementations. If a program is moved to an
implementation for which Find is O(N), that program could be
unusable when the maps are large. We allow O(log N) access because
the proportionality constant and caching effects are likely to be
larger than the log factor, and we don't want to discourage
innovative implementations.
Extensions to Ada 95
62.c/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Hashed_Maps is new.
A.18.6 The Package Containers.Ordered_Maps
Static Semantics
1/2 {AI95-00302-03} The generic library package Containers.Ordered_Maps has
the following declaration:
2/2 generic
type Key_Type is private;
type Element_Type is private;
with function "<" (Left, Right : Key_Type) return Boolean is <>;
with function "=" (Left, Right : Element_Type) return Boolean is <>;
package Ada.Containers.Ordered_Maps is
pragma Preelaborate(Ordered_Maps);
3/2 function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
4/2 type Map is tagged private;
pragma Preelaborable_Initialization(Map);
5/2 type Cursor is private;
pragma Preelaborable_Initialization(Cursor);
6/2 Empty_Map : constant Map;
7/2 No_Element : constant Cursor;
8/2 function "=" (Left, Right : Map) return Boolean;
9/2 function Length (Container : Map) return Count_Type;
10/2 function Is_Empty (Container : Map) return Boolean;
11/2 procedure Clear (Container : in out Map);
12/2 function Key (Position : Cursor) return Key_Type;
13/2 function Element (Position : Cursor) return Element_Type;
14/2 procedure Replace_Element (Container : in out Map;
Position : in Cursor;
New_Item : in Element_Type);
15/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Key : in Key_Type;
Element : in Element_Type));
16/2 procedure Update_Element
(Container : in out Map;
Position : in Cursor;
Process : not null access procedure
(Key : in Key_Type;
Element : in out Element_Type));
17/2 procedure Move (Target : in out Map;
Source : in out Map);
18/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type;
Position : out Cursor;
Inserted : out Boolean);
19/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
Position : out Cursor;
Inserted : out Boolean);
20/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type);
21/2 procedure Include (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type);
22/2 procedure Replace (Container : in out Map;
Key : in Key_Type;
New_Item : in Element_Type);
23/2 procedure Exclude (Container : in out Map;
Key : in Key_Type);
24/2 procedure Delete (Container : in out Map;
Key : in Key_Type);
25/2 procedure Delete (Container : in out Map;
Position : in out Cursor);
26/2 procedure Delete_First (Container : in out Map);
27/2 procedure Delete_Last (Container : in out Map);
28/2 function First (Container : Map) return Cursor;
29/2 function First_Element (Container : Map) return Element_Type;
30/2 function First_Key (Container : Map) return Key_Type;
31/2 function Last (Container : Map) return Cursor;
32/2 function Last_Element (Container : Map) return Element_Type;
33/2 function Last_Key (Container : Map) return Key_Type;
34/2 function Next (Position : Cursor) return Cursor;
35/2 procedure Next (Position : in out Cursor);
36/2 function Previous (Position : Cursor) return Cursor;
37/2 procedure Previous (Position : in out Cursor);
38/2 function Find (Container : Map;
Key : Key_Type) return Cursor;
39/2 function Element (Container : Map;
Key : Key_Type) return Element_Type;
40/2 function Floor (Container : Map;
Key : Key_Type) return Cursor;
41/2 function Ceiling (Container : Map;
Key : Key_Type) return Cursor;
42/2 function Contains (Container : Map;
Key : Key_Type) return Boolean;
43/2 function Has_Element (Position : Cursor) return Boolean;
44/2 function "<" (Left, Right : Cursor) return Boolean;
45/2 function ">" (Left, Right : Cursor) return Boolean;
46/2 function "<" (Left : Cursor; Right : Key_Type) return Boolean;
47/2 function ">" (Left : Cursor; Right : Key_Type) return Boolean;
48/2 function "<" (Left : Key_Type; Right : Cursor) return Boolean;
49/2 function ">" (Left : Key_Type; Right : Cursor) return Boolean;
50/2 procedure Iterate
(Container : in Map;
Process : not null access procedure (Position : in Cursor));
51/2 procedure Reverse_Iterate
(Container : in Map;
Process : not null access procedure (Position : in Cursor));
52/2 private
53/2 ... -- not specified by the language
54/2 end Ada.Containers.Ordered_Maps;
55/2 {AI95-00302-03} {equivalent key (of an ordered map)} Two keys K1 and K2
are equivalent if both K1 < K2 and K2 < K1 return False, using the generic
formal "<" operator for keys. Function Equivalent_Keys returns True if Left
and Right are equivalent, and False otherwise.
56/2 {AI95-00302-03} The actual function for the generic formal function "<"
on Key_Type values is expected to return the same value each time it is called
with a particular pair of key values. It should define a strict ordering
relationship, that is, be irreflexive, asymmetric, and transitive. If the
actual for "<" behaves in some other manner, the behavior of this package is
unspecified. Which subprograms of this package call "<" and how many times
they call it, is unspecified.{unspecified [partial]}
56.a/2 Implementation Note: The implementation is not required to protect
against "<" raising an exception, or returning random results, or
any other "bad" behavior. It's not practical to do so, and a
broken "<" function makes the container unusable.
56.b/2 The implementation can call "<" whenever it is needed; we don't
want to specify how often that happens. The result must remain the
same (this is a logically pure function), or the behavior is
unspecified.
57/2 {AI95-00302-03} If the value of a key stored in a map is changed other
than by an operation in this package such that at least one of "<" or "=" give
different results, the behavior of this package is unspecified.{unspecified
[partial]}
57.a/2 Implementation Note: The implementation is not required to protect
against changes to key values other than via the operations
declared in the Ordered_Maps package.
57.b/2 To see how this could happen, imagine an instance of Ordered_Maps
package where the key type is an access-to-variable type and "<"
returns a value derived from comparing the components of the
designated objects. Then, any operation that has a key value (even
if the key value is constant) could modify those components and
change the result of "<":
57.c/2 Key (Map).Some_Component := New_Value;
57.d/2 This is really a design error on the part of the user of the map;
it shouldn't be possible to modify keys stored in a map such that
"<" changes. But we can't prevent this error anymore than we can
prevent someone passing as "<" a routine that produces random
answers.
58/2 {AI95-00302-03} {first node (of an ordered map)}
{last node (of an ordered map)} {successor node (of an ordered map)} The first
node of a nonempty map is the one whose key is less than the key of all the
other nodes in the map. The last node of a nonempty map is the one whose key
is greater than the key of all the other elements in the map. The successor of
a node is the node with the smallest key that is larger than the key of the
given node. The predecessor of a node is the node with the largest key that is
smaller than the key of the given node. All comparisons are done using the
generic formal "<" operator for keys.
59/2 procedure Delete_First (Container : in out Map);
60/2 {AI95-00302-03} If Container is empty, Delete_First has no effect.
Otherwise the node designated by First (Container) is removed from
Container. Delete_First tampers with the cursors of Container.
61/2 procedure Delete_Last (Container : in out Map);
62/2 {AI95-00302-03} If Container is empty, Delete_Last has no effect.
Otherwise the node designated by Last (Container) is removed from
Container. Delete_Last tampers with the cursors of Container.
63/2 function First_Element (Container : Map) return Element_Type;
64/2 {AI95-00302-03} Equivalent to Element (First (Container)).
65/2 function First_Key (Container : Map) return Key_Type;
66/2 {AI95-00302-03} Equivalent to Key (First (Container)).
67/2 function Last (Container : Map) return Cursor;
68/2 {AI95-00302-03} Returns a cursor that designates the last node in
Container. If Container is empty, returns No_Element.
69/2 function Last_Element (Container : Map) return Element_Type;
70/2 {AI95-00302-03} Equivalent to Element (Last (Container)).
71/2 function Last_Key (Container : Map) return Key_Type;
72/2 {AI95-00302-03} Equivalent to Key (Last (Container)).
73/2 function Previous (Position : Cursor) return Cursor;
74/2 {AI95-00302-03} If Position equals No_Element, then Previous
returns No_Element. Otherwise Previous returns a cursor
designating the node that precedes the one designated by Position.
If Position designates the first element, then Previous returns
No_Element.
75/2 procedure Previous (Position : in out Cursor);
76/2 {AI95-00302-03} Equivalent to Position := Previous (Position).
77/2 function Floor (Container : Map;
Key : Key_Type) return Cursor;
78/2 {AI95-00302-03} Floor searches for the last node whose key is not
greater than Key, using the generic formal "<" operator for keys.
If such a node is found, a cursor that designates it is returned.
Otherwise No_Element is returned.
79/2 function Ceiling (Container : Map;
Key : Key_Type) return Cursor;
80/2 {AI95-00302-03} Ceiling searches for the first node whose key is
not less than Key, using the generic formal "<" operator for keys.
If such a node is found, a cursor that designates it is returned.
Otherwise No_Element is returned.
81/2 function "<" (Left, Right : Cursor) return Boolean;
82/2 {AI95-00302-03} Equivalent to Key (Left) < Key (Right).
83/2 function ">" (Left, Right : Cursor) return Boolean;
84/2 {AI95-00302-03} Equivalent to Key (Right) < Key (Left).
85/2 function "<" (Left : Cursor; Right : Key_Type) return Boolean;
86/2 {AI95-00302-03} Equivalent to Key (Left) < Right.
87/2 function ">" (Left : Cursor; Right : Key_Type) return Boolean;
88/2 {AI95-00302-03} Equivalent to Right < Key (Left).
89/2 function "<" (Left : Key_Type; Right : Cursor) return Boolean;
90/2 {AI95-00302-03} Equivalent to Left < Key (Right).
91/2 function ">" (Left : Key_Type; Right : Cursor) return Boolean;
92/2 {AI95-00302-03} Equivalent to Key (Right) < Left.
93/2 procedure Reverse_Iterate
(Container : in Map;
Process : not null access procedure (Position : in Cursor));
94/2 {AI95-00302-03} Iterates over the nodes in Container as per
Iterate, with the difference that the nodes are traversed in
predecessor order, starting with the last node.
Implementation Advice
95/2 {AI95-00302-03} If N is the length of a map, then the worst-case time
complexity of the Element, Insert, Include, Replace, Delete, Exclude and Find
operations that take a key parameter should be O((log N)**2) or better. The
worst-case time complexity of the subprograms that take a cursor parameter
should be O(1).
95.a/2 Implementation Advice: The worst-case time complexity of Element,
Insert, Include, Replace, Delete, Exclude and Find operations that
take a key parameter for Containers.Ordered_Maps should be O((log
N)**2) or better. The worst-case time complexity of the
subprograms of Containers.Ordered_Maps that take a cursor
parameter should be O(1).
95.b/2 Implementation Note: A balanced (red-black) tree for keys has
O(log N) worst-case performance. Note that a O(N) worst-case
implementation (like a list) would be wrong.
95.c/2 Reason: We do not mean to overly constrain implementation
strategies here. However, it is important for portability that the
performance of large containers has roughly the same factors on
different implementations. If a program is moved to an
implementation that takes O(N) to find elements, that program
could be unusable when the maps are large. We allow the extra log
N factors because the proportionality constant and caching effects
are likely to be larger than the log factor, and we don't want to
discourage innovative implementations.
Extensions to Ada 95
95.d/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Ordered_Maps is new.
A.18.7 Sets
1/2 {AI95-00302-03} The language-defined generic packages
Containers.Hashed_Sets and Containers.Ordered_Sets provide private types Set
and Cursor, and a set of operations for each type. A set container allows
elements of an arbitrary type to be stored without duplication. A hashed set
uses a hash function to organize elements, while an ordered set orders its
element per a specified relation.{set container} {container (set)}
2/2 {AI95-00302-03} This section describes the declarations that are common to
both kinds of sets. See A.18.8 for a description of the semantics specific to
Containers.Hashed_Sets and A.18.9 for a description of the semantics specific
to Containers.Ordered_Sets.
Static Semantics
3/2 {AI95-00302-03} The actual function for the generic formal function "=" on
Element_Type values is expected to define a reflexive and symmetric
relationship and return the same result value each time it is called with a
particular pair of values. If it behaves in some other manner, the function
"=" on set values returns an unspecified value. The exact arguments and number
of calls of this generic formal function by the function "=" on set values are
unspecified.{unspecified [partial]}
3.a/2 Ramification: If the actual function for "=" is not symmetric and
consistent, the result returned by the "=" for Set objects cannot
be predicted. The implementation is not required to protect
against "=" raising an exception, or returning random results, or
any other "bad" behavior. And it can call "=" in whatever manner
makes sense. But note that only the result of "=" for Set objects
is unspecified; other subprograms are not allowed to break if "="
is bad (they aren't expected to use "=").
4/2 {AI95-00302-03} The type Set is used to represent sets. The type Set needs
finalization (see 7.6).
5/2 {AI95-00302-03} A set contains elements. Set cursors designate elements.
There exists an equivalence relation on elements, whose definition is
different for hashed sets and ordered sets. A set never contains two or more
equivalent elements. The length of a set is the number of elements it
contains.{length (of a set)}
6/2 {AI95-00302-03} {first element (of a set)} {last element (of a set)}
{successor element (of a set)} Each nonempty set has two particular elements
called the first element and the last element (which may be the same). Each
element except for the last element has a successor element. If there are no
other intervening operations, starting with the first element and repeatedly
going to the successor element will visit each element in the set exactly once
until the last element is reached. The exact definition of these terms is
different for hashed sets and ordered sets.
7/2 {AI95-00302-03} [Some operations of these generic packages have
access-to-subprogram parameters. To ensure such operations are well-defined,
they guard against certain actions by the designated subprogram. In
particular, some operations check for "tampering with cursors" of a container
because they depend on the set of elements of the container remaining
constant, and others check for "tampering with elements" of a container
because they depend on elements of the container not being replaced.]
8/2 {AI95-00302-03} {tamper with cursors (of a set)} A subprogram is said to
tamper with cursors of a set object S if:
9/2 * it inserts or deletes elements of S, that is, it calls the Insert,
Include, Clear, Delete, Exclude, or Replace_Element procedures with S
as a parameter; or
9.a/2 To be honest: Operations which are defined to be equivalent to a
call on one of these operations also are included. Similarly,
operations which call one of these as part of their definition are
included.
9.b/2 Discussion: We have to include Replace_Element here because it
might delete and reinsert the element if it moves in the set. That
could change the order of iteration, which is what this check is
designed to prevent. Replace is also included, as it is defined in
terms of Replace_Element.
10/2 * it finalizes S; or
11/2 * it calls the Move procedure with S as a parameter; or
12/2 * it calls one of the operations defined to tamper with cursors of S.
13/2 {AI95-00302-03} {tamper with elements (of a set)} A subprogram is said to
tamper with elements of a set object S if:
14/2 * it tampers with cursors of S.
14.a/2 Reason: Complete replacement of an element can cause its memory to
be deallocated while another operation is holding onto a reference
to it. That can't be allowed. However, a simple modification of
(part of) an element is not a problem, so
Update_Element_Preserving_Key does not cause a problem.
14.b/2 We don't need to list Replace and Replace_Element here because
they are covered by "tamper with cursors". For Set, "tamper with
cursors" and "tamper with elements" are the same. We leave both
terms so that the rules for routines like Iterate and
Query_Element are consistent across all containers.
15/2 {AI95-00302-03} Empty_Set represents the empty Set object. It has a
length of 0. If an object of type Set is not otherwise initialized, it is
initialized to the same value as Empty_Set.
16/2 {AI95-00302-03} No_Element represents a cursor that designates no
element. If an object of type Cursor is not otherwise initialized, it is
initialized to the same value as No_Element.
17/2 {AI95-00302-03} The predefined "=" operator for type Cursor returns True
if both cursors are No_Element, or designate the same element in the same
container.
18/2 {AI95-00302-03} Execution of the default implementation of the Input,
Output, Read, or Write attribute of type Cursor raises Program_Error.
18.a/2 Reason: A cursor will probably be implemented in terms of one or
more access values, and the effects of streaming access values is
unspecified. Rather than letting the user stream junk by accident,
we mandate that streaming of cursors raise Program_Error by
default. The attributes can always be specified if there is a need
to support streaming.
19/2 function "=" (Left, Right : Set) return Boolean;
20/2 {AI95-00302-03} If Left and Right denote the same set object, then
the function returns True. If Left and Right have different
lengths, then the function returns False. Otherwise, for each
element E in Left, the function returns False if an element equal
to E (using the generic formal equality operator) is not present
in Right. If the function has not returned a result after checking
all of the elements, it returns True. Any exception raised during
evaluation of element equality is propagated.
20.a/2 Implementation Note: This wording describes the canonical
semantics. However, the order and number of calls on the formal
equality function is unspecified for all of the operations that
use it in this package, so an implementation can call it as many
or as few times as it needs to get the correct answer.
Specifically, there is no requirement to call the formal equality
additional times once the answer has been determined.
21/2 function Equivalent_Sets (Left, Right : Set) return Boolean;
22/2 {AI95-00302-03} If Left and Right denote the same set object, then
the function returns True. If Left and Right have different
lengths, then the function returns False. Otherwise, for each
element E in Left, the function returns False if an element
equivalent to E is not present in Right. If the function has not
returned a result after checking all of the elements, it returns
True. Any exception raised during evaluation of element
equivalence is propagated.
23/2 function To_Set (New_Item : Element_Type) return Set;
24/2 {AI95-00302-03} Returns a set containing the single element
New_Item.
25/2 function Length (Container : Set) return Count_Type;
26/2 {AI95-00302-03} Returns the number of elements in Container.
27/2 function Is_Empty (Container : Set) return Boolean;
28/2 {AI95-00302-03} Equivalent to Length (Container) = 0.
29/2 procedure Clear (Container : in out Set);
30/2 {AI95-00302-03} Removes all the elements from Container.
31/2 function Element (Position : Cursor) return Element_Type;
32/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. Otherwise, Element returns the
element designated by Position.
33/2 procedure Replace_Element (Container : in out Set;
Position : in Cursor;
New_Item : in Element_Type);
34/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated; if Position does not designate an
element in Container, then Program_Error is propagated. If an
element equivalent to New_Item is already present in Container at
a position other than Position, Program_Error is propagated.
Otherwise, Replace_Element assigns New_Item to the element
designated by Position. Any exception raised by the assignment is
propagated.
34.a/2 Implementation Note: The final assignment may require that the
node of the element be moved in the Set's data structures. That
could mean that implementing this operation exactly as worded
above could require the overhead of searching twice.
Implementations are encouraged to avoid this extra overhead when
possible, by prechecking if the old element is equivalent to the
new one, by inserting a placeholder node while checking for an
equivalent element, and similar optimizations.
34.b/2 The cursor still designates the same element after this operation;
only the value of that element has changed. Cursors cannot include
information about the relative position of an element in a Set (as
they must survive insertions and deletions of other elements), so
this should not pose an implementation hardship.
35/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Element : in Element_Type));
36/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. Otherwise, Query_Element calls
Process.all with the element designated by Position as the
argument. Program_Error is propagated if Process.all tampers with
the elements of Container. Any exception raised by Process.all is
propagated.
37/2 procedure Move (Target : in out Set;
Source : in out Set);
38/2 {AI95-00302-03} If Target denotes the same object as Source, then
Move has no effect. Otherwise, Move first clears Target. Then,
each element from Source is removed from Source and inserted into
Target. The length of Source is 0 after a successful call to Move.
39/2 procedure Insert (Container : in out Set;
New_Item : in Element_Type;
Position : out Cursor;
Inserted : out Boolean);
40/2 {AI95-00302-03} Insert checks if an element equivalent to New_Item
is already present in Container. If a match is found, Inserted is
set to False and Position designates the matching element.
Otherwise, Insert adds New_Item to Container; Inserted is set to
True and Position designates the newly-inserted element. Any
exception raised during allocation is propagated and Container is
not modified.
41/2 procedure Insert (Container : in out Set;
New_Item : in Element_Type);
42/2 {AI95-00302-03} Insert inserts New_Item into Container as per the
four-parameter Insert, with the difference that if an element
equivalent to New_Item is already in the set, then
Constraint_Error is propagated.
42.a/2 Discussion: This is equivalent to:
42.b/2 declare
Inserted : Boolean; C : Cursor;
begin
Insert (Container, New_Item, C, Inserted);
if not Inserted then
raise Constraint_Error;
end if;
end;
42.c/2 but doesn't require the hassle of out parameters.
43/2 procedure Include (Container : in out Set;
New_Item : in Element_Type);
44/2 {AI95-00302-03} Include inserts New_Item into Container as per the
four-parameter Insert, with the difference that if an element
equivalent to New_Item is already in the set, then it is replaced.
Any exception raised during assignment is propagated.
45/2 procedure Replace (Container : in out Set;
New_Item : in Element_Type);
46/2 {AI95-00302-03} Replace checks if an element equivalent to
New_Item is already in the set. If a match is found, that element
is replaced with New_Item; otherwise, Constraint_Error is
propagated.
47/2 procedure Exclude (Container : in out Set;
Item : in Element_Type);
48/2 {AI95-00302-03} Exclude checks if an element equivalent to Item is
present in Container. If a match is found, Exclude removes the
element from the set.
49/2 procedure Delete (Container : in out Set;
Item : in Element_Type);
50/2 {AI95-00302-03} Delete checks if an element equivalent to Item is
present in Container. If a match is found, Delete removes the
element from the set; otherwise, Constraint_Error is propagated.
51/2 procedure Delete (Container : in out Set;
Position : in out Cursor);
52/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated. If Position does not designate an
element in Container, then Program_Error is propagated. Otherwise,
Delete removes the element designated by Position from the set.
Position is set to No_Element on return.
52.a/2 Ramification: The check on Position checks that the cursor does
not belong to some other set. This check implies that a reference
to the set is included in the cursor value. This wording is not
meant to require detection of dangling cursors; such cursors are
defined to be invalid, which means that execution is erroneous,
and any result is allowed (including not raising an exception).
53/2 procedure Union (Target : in out Set;
Source : in Set);
54/2 {AI95-00302-03} Union inserts into Target the elements of Source
that are not equivalent to some element already in Target.
54.a/2 Implementation Note: If the objects are the same, the result is
the same as the original object. The implementation needs to take
care so that aliasing effects do not make the result trash; Union
(S, S); must work.
55/2 function Union (Left, Right : Set) return Set;
56/2 {AI95-00302-03} Returns a set comprising all of the elements of
Left, and the elements of Right that are not equivalent to some
element of Left.
57/2 procedure Intersection (Target : in out Set;
Source : in Set);
58/2 {AI95-00302-03} Union deletes from Target the elements of Target
that are not equivalent to some element of Source.
58.a/2 Implementation Note: If the objects are the same, the result is
the same as the original object. The implementation needs to take
care so that aliasing effects do not make the result trash;
Intersection (S, S); must work.
59/2 function Intersection (Left, Right : Set) return Set;
60/2 {AI95-00302-03} Returns a set comprising all the elements of Left
that are equivalent to the some element of Right.
61/2 procedure Difference (Target : in out Set;
Source : in Set);
62/2 {AI95-00302-03} If Target denotes the same object as Source, then
Difference clears Target. Otherwise, it deletes from Target the
elements that are equivalent to some element of Source.
63/2 function Difference (Left, Right : Set) return Set;
64/2 {AI95-00302-03} Returns a set comprising the elements of Left that
are not equivalent to some element of Right.
65/2 procedure Symmetric_Difference (Target : in out Set;
Source : in Set);
66/2 {AI95-00302-03} If Target denotes the same object as Source, then
Symmetric_Difference clears Target. Otherwise, it deletes from
Target the elements that are equivalent to some element of Source,
and inserts into Target the elements of Source that are not
equivalent to some element of Target.
67/2 function Symmetric_Difference (Left, Right : Set) return Set;
68/2 {AI95-00302-03} Returns a set comprising the elements of Left that
are not equivalent to some element of Right, and the elements of
Right that are not equivalent to some element of Left.
69/2 function Overlap (Left, Right : Set) return Boolean;
70/2 {AI95-00302-03} If an element of Left is equivalent to some
element of Right, then Overlap returns True. Otherwise it returns
False.
70.a/2 Discussion: This operation is commutative. If Overlap returns
False, the two sets are disjoint.
71/2 function Is_Subset (Subset : Set;
Of_Set : Set) return Boolean;
72/2 {AI95-00302-03} If an element of Subset is not equivalent to some
element of Of_Set, then Is_Subset returns False. Otherwise it
returns True.
72.a/2 Discussion: This operation is not commutative, so we use parameter
names that make it clear in named notation which set is which.
73/2 function First (Container : Set) return Cursor;
74/2 {AI95-00302-03} If Length (Container) = 0, then First returns
No_Element. Otherwise, First returns a cursor that designates the
first element in Container.
75/2 function Next (Position : Cursor) return Cursor;
76/2 {AI95-00302-03} Returns a cursor that designates the successor of
the element designated by Position. If Position designates the
last element, then No_Element is returned. If Position equals
No_Element, then No_Element is returned.
77/2 procedure Next (Position : in out Cursor);
78/2 {AI95-00302-03} Equivalent to Position := Next (Position).
79/2 {AI95-00302-03} Equivalent to Find (Container, Item) /= No_Element.
80/2 function Find (Container : Set;
Item : Element_Type) return Cursor;
81/2 {AI95-00302-03} If Length (Container) equals 0, then Find returns
No_Element. Otherwise, Find checks if an element equivalent to
Item is present in Container. If a match is found, a cursor
designating the matching element is returned; otherwise,
No_Element is returned.
82/2 function Contains (Container : Set;
Item : Element_Type) return Boolean;
83/2 function Has_Element (Position : Cursor) return Boolean;
84/2 {AI95-00302-03} Returns True if Position designates an element,
and returns False otherwise.
84.a/2 To be honest: This function may not detect cursors that designate
deleted elements; such cursors are invalid (see below); the result
of Has_Element for invalid cursors is unspecified (but not
erroneous).
85/2 procedure Iterate
(Container : in Set;
Process : not null access procedure (Position : in Cursor));
86/2 {AI95-00302-03} Iterate calls Process.all with a cursor that
designates each element in Container, starting with the first
element and moving the cursor according to the successor relation.
Program_Error is propagated if Process.all tampers with the
cursors of Container. Any exception raised by Process.all is
propagated.
86.a/2 Implementation Note: The "tamper with cursors" check takes place
when the operations that insert or delete elements, and so on are
called.
86.b/2 See Iterate for vectors (A.18.2) for a suggested implementation of
the check.
87/2 {AI95-00302-03} Both Containers.Hashed_Set and Containers.Ordered_Set
declare a nested generic package Generic_Keys, which provides operations that
allow set manipulation in terms of a key (typically, a portion of an element)
instead of a complete element. The formal function Key of Generic_Keys
extracts a key value from an element. It is expected to return the same value
each time it is called with a particular element. The behavior of Generic_Keys
is unspecified if Key behaves in some other manner.{unspecified [partial]}
88/2 {AI95-00302-03} A key is expected to unambiguously determine a single
equivalence class for elements. The behavior of Generic_Keys is unspecified if
the formal parameters of this package behave in some other
manner.{unspecified [partial]}
89/2 function Key (Position : Cursor) return Key_Type;
90/2 {AI95-00302-03} Equivalent to Key (Element (Position)).
91/2 {AI95-00302-03} The subprograms in package Generic_Keys named Contains,
Find, Element, Delete, and Exclude, are equivalent to the corresponding
subprograms in the parent package, with the difference that the Key parameter
is used to locate an element in the set.
92/2 procedure Replace (Container : in out Set;
Key : in Key_Type;
New_Item : in Element_Type);
93/2 {AI95-00302-03} Equivalent to Replace_Element (Container, Find
(Container, Key), New_Item).
94/2 procedure Update_Element_Preserving_Key
(Container : in out Set;
Position : in Cursor;
Process : not null access procedure
(Element : in out Element_Type));
95/2 {AI95-00302-03} If Position equals No_Element, then
Constraint_Error is propagated; if Position does not designate an
element in Container, then Program_Error is propagated. Otherwise,
Update_Element_Preserving_Key uses Key to save the key value K of
the element designated by Position. Update_Element_Preserving_Key
then calls Process.all with that element as the argument.
Program_Error is propagated if Process.all tampers with the
elements of Container. Any exception raised by Process.all is
propagated. After Process.all returns,
Update_Element_Preserving_Key checks if K determines the same
equivalence class as that for the new element; if not, the element
is removed from the set and Program_Error is propagated.
95.a/2 Reason: The key check ensures that the invariants of the set are
preserved by the modification. The "tampers with the elements"
check prevents data loss (if Element_Type is by-copy) or erroneous
execution (if element type is unconstrained and indefinite).
96/2 If Element_Type is unconstrained and definite, then the actual
Element parameter of Process.all shall be unconstrained.
96.a/2 Ramification: This means that the elements cannot be directly
allocated from the heap; it must be possible to change the
discriminants of the element in place.
Erroneous Execution
97/2 {AI95-00302-03} A Cursor value is invalid if any of the following have
occurred since it was created:{invalid cursor (of a set)} {cursor (invalid)
[partial]}
98/2 * The set that contains the element it designates has been finalized;
99/2 * The set that contains the element it designates has been used as the
Source or Target of a call to Move; or
100/2 * The element it designates has been deleted from the set.
101/2 {AI95-00302-03} The result of "=" or Has_Element is unspecified if these
functions are called with an invalid cursor parameter.{unspecified
[partial]} Execution is erroneous if any other subprogram declared in
Containers.Hashed_Sets or Containers.Ordered_Sets is called with an invalid
cursor parameter.{erroneous execution (cause) [partial]}
101.a/2 Discussion: The list above is intended to be exhaustive. In other
cases, a cursor value continues to designate its original element.
For instance, cursor values survive the insertion and deletion of
other elements.
101.b/2 While it is possible to check for these cases, in many cases the
overhead necessary to make the check is substantial in time or
space. Implementations are encouraged to check for as many of
these cases as possible and raise Program_Error if detected.
Implementation Requirements
102/2 {AI95-00302-03} No storage associated with a Set object shall be lost
upon assignment or scope exit.
103/2 {AI95-00302-03} The execution of an assignment_statement for a set shall
have the effect of copying the elements from the source set object to the
target set object.
103.a/2 Implementation Note: An assignment of a Set is a "deep" copy; that
is the elements are copied as well as the data structures. We say
"effect of" in order to allow the implementation to avoid copying
elements immediately if it wishes. For instance, an implementation
that avoided copying until one of the containers is modified would
be allowed.
Implementation Advice
104/2 {AI95-00302-03} Move should not copy elements, and should minimize
copying of internal data structures.
104.a/2 Implementation Advice: Move for sets should not copy elements, and
should minimize copying of internal data structures.
104.b/2 Implementation Note: Usually that can be accomplished simply by
moving the pointer(s) to the internal data structures from the
Source container to the Target container.
105/2 {AI95-00302-03} If an exception is propagated from a set operation, no
storage should be lost, nor any elements removed from a set unless specified
by the operation.
105.a/2 Implementation Advice: If an exception is propagated from a set
operation, no storage should be lost, nor any elements removed
from a set unless specified by the operation.
105.b/2 Reason: This is important so that programs can recover from
errors. But we don't want to require heroic efforts, so we just
require documentation of cases where this can't be accomplished.
Wording Changes from Ada 95
105.c/2 {AI95-00302-03} This description of sets is new; the extensions
are documented with the specific packages.
A.18.8 The Package Containers.Hashed_Sets
Static Semantics
1/2 {AI95-00302-03} The generic library package Containers.Hashed_Sets has the
following declaration:
2/2 generic
type Element_Type is private;
with function Hash (Element : Element_Type) return Hash_Type;
with function Equivalent_Elements (Left, Right : Element_Type)
return Boolean;
with function "=" (Left, Right : Element_Type) return Boolean is <>;
package Ada.Containers.Hashed_Sets is
pragma Preelaborate(Hashed_Sets);
3/2 type Set is tagged private;
pragma Preelaborable_Initialization(Set);
4/2 type Cursor is private;
pragma Preelaborable_Initialization(Cursor);
5/2 Empty_Set : constant Set;
6/2 No_Element : constant Cursor;
7/2 function "=" (Left, Right : Set) return Boolean;
8/2 function Equivalent_Sets (Left, Right : Set) return Boolean;
9/2 function To_Set (New_Item : Element_Type) return Set;
10/2 function Capacity (Container : Set) return Count_Type;
11/2 procedure Reserve_Capacity (Container : in out Set;
Capacity : in Count_Type);
12/2 function Length (Container : Set) return Count_Type;
13/2 function Is_Empty (Container : Set) return Boolean;
14/2 procedure Clear (Container : in out Set);
15/2 function Element (Position : Cursor) return Element_Type;
16/2 procedure Replace_Element (Container : in out Set;
Position : in Cursor;
New_Item : in Element_Type);
17/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Element : in Element_Type));
18/2 procedure Move (Target : in out Set;
Source : in out Set);
19/2 procedure Insert (Container : in out Set;
New_Item : in Element_Type;
Position : out Cursor;
Inserted : out Boolean);
20/2 procedure Insert (Container : in out Set;
New_Item : in Element_Type);
21/2 procedure Include (Container : in out Set;
New_Item : in Element_Type);
22/2 procedure Replace (Container : in out Set;
New_Item : in Element_Type);
23/2 procedure Exclude (Container : in out Set;
Item : in Element_Type);
24/2 procedure Delete (Container : in out Set;
Item : in Element_Type);
25/2 procedure Delete (Container : in out Set;
Position : in out Cursor);
26/2 procedure Union (Target : in out Set;
Source : in Set);
27/2 function Union (Left, Right : Set) return Set;
28/2 function "or" (Left, Right : Set) return Set renames Union;
29/2 procedure Intersection (Target : in out Set;
Source : in Set);
30/2 function Intersection (Left, Right : Set) return Set;
31/2 function "and" (Left, Right : Set) return Set renames Intersection;
32/2 procedure Difference (Target : in out Set;
Source : in Set);
33/2 function Difference (Left, Right : Set) return Set;
34/2 function "-" (Left, Right : Set) return Set renames Difference;
35/2 procedure Symmetric_Difference (Target : in out Set;
Source : in Set);
36/2 function Symmetric_Difference (Left, Right : Set) return Set;
37/2 function "xor" (Left, Right : Set) return Set
renames Symmetric_Difference;
38/2 function Overlap (Left, Right : Set) return Boolean;
39/2 function Is_Subset (Subset : Set;
Of_Set : Set) return Boolean;
40/2 function First (Container : Set) return Cursor;
41/2 function Next (Position : Cursor) return Cursor;
42/2 procedure Next (Position : in out Cursor);
43/2 function Find (Container : Set;
Item : Element_Type) return Cursor;
44/2 function Contains (Container : Set;
Item : Element_Type) return Boolean;
45/2 function Has_Element (Position : Cursor) return Boolean;
46/2 function Equivalent_Elements (Left, Right : Cursor)
return Boolean;
47/2 function Equivalent_Elements (Left : Cursor;
Right : Element_Type)
return Boolean;
48/2 function Equivalent_Elements (Left : Element_Type;
Right : Cursor)
return Boolean;
49/2 procedure Iterate
(Container : in Set;
Process : not null access procedure (Position : in Cursor));
50/2 generic
type Key_Type (<>) is private;
with function Key (Element : Element_Type) return Key_Type;
with function Hash (Key : Key_Type) return Hash_Type;
with function Equivalent_Keys (Left, Right : Key_Type)
return Boolean;
package Generic_Keys is
51/2 function Key (Position : Cursor) return Key_Type;
52/2 function Element (Container : Set;
Key : Key_Type)
return Element_Type;
53/2 procedure Replace (Container : in out Set;
Key : in Key_Type;
New_Item : in Element_Type);
54/2 procedure Exclude (Container : in out Set;
Key : in Key_Type);
55/2 procedure Delete (Container : in out Set;
Key : in Key_Type);
56/2 function Find (Container : Set;
Key : Key_Type)
return Cursor;
57/2 function Contains (Container : Set;
Key : Key_Type)
return Boolean;
58/2 procedure Update_Element_Preserving_Key
(Container : in out Set;
Position : in Cursor;
Process : not null access procedure
(Element : in out Element_Type));
59/2 end Generic_Keys;
60/2 private
61/2 ... -- not specified by the language
62/2 end Ada.Containers.Hashed_Sets;
63/2 {AI95-00302-03} {capacity (of a hashed set)} An object of type Set
contains an expandable hash table, which is used to provide direct access to
elements. The capacity of an object of type Set is the maximum number of
elements that can be inserted into the hash table prior to it being
automatically expanded.
64/2 {AI95-00302-03} {equivalent element (of a hashed set)} Two elements E1
and E2 are defined to be equivalent if Equivalent_Elements (E1, E2) returns
True.
65/2 {AI95-00302-03} The actual function for the generic formal function Hash
is expected to return the same value each time it is called with a particular
element value. For any two equivalent elements, the actual for Hash is
expected to return the same value. If the actual for Hash behaves in some
other manner, the behavior of this package is unspecified. Which subprograms
of this package call Hash, and how many times they call it, is
unspecified.{unspecified [partial]}
66/2 {AI95-00302-03} The actual function for the generic formal function
Equivalent_Elements is expected to return the same value each time it is
called with a particular pair of Element values. It should define an
equivalence relationship, that is, be reflexive, symmetric, and transitive. If
the actual for Equivalent_Elements behaves in some other manner, the behavior
of this package is unspecified. Which subprograms of this package call
Equivalent_Elements, and how many times they call it, is
unspecified.{unspecified [partial]}
67/2 {AI95-00302-03} If the value of an element stored in a set is changed
other than by an operation in this package such that at least one of Hash or
Equivalent_Elements give different results, the behavior of this package is
unspecified.{unspecified [partial]}
67.a/2 Discussion: See A.18.5, "The Package Containers.Hashed_Maps" for a
suggested implementation, and for justification of the
restrictions regarding Hash and Equivalent_Elements. Note that
sets only need to store elements, not key/element pairs.
68/2 {AI95-00302-03} {first element (of a hashed set)}
{last element (of a hashed set)} {successor element (of a hashed set)} Which
elements are the first element and the last element of a set, and which
element is the successor of a given element, are unspecified, other than the
general semantics described in A.18.7.{unspecified [partial]}
69/2 function Capacity (Container : Set) return Count_Type;
70/2 {AI95-00302-03} Returns the capacity of Container.
71/2 procedure Reserve_Capacity (Container : in out Set;
Capacity : in Count_Type);
72/2 {AI95-00302-03} Reserve_Capacity allocates a new hash table such
that the length of the resulting set can become at least the value
Capacity without requiring an additional call to Reserve_Capacity,
and is large enough to hold the current length of Container.
Reserve_Capacity then rehashes the elements in Container onto the
new hash table. It replaces the old hash table with the new hash
table, and then deallocates the old hash table. Any exception
raised during allocation is propagated and Container is not
modified.
73/2 Reserve_Capacity tampers with the cursors of Container.
73.a/2 Reason: Reserve_Capacity tampers with the cursors, as rehashing
probably will change the relationships of the elements in
Container.
74/2 procedure Clear (Container : in out Set);
75/2 {AI95-00302-03} In addition to the semantics described in A.18.7,
Clear does not affect the capacity of Container.
76/2 procedure Insert (Container : in out Set;
New_Item : in Element_Type;
Position : out Cursor;
Inserted : out Boolean);
77/2 {AI95-00302-03} In addition to the semantics described in A.18.7,
if Length (Container) equals Capacity (Container), then Insert
first calls Reserve_Capacity to increase the capacity of Container
to some larger value.
78/2 function First (Container : Set) return Cursor;
79/2 {AI95-00302-03} If Length (Container) = 0, then First returns
No_Element. Otherwise, First returns a cursor that designates the
first hashed element in Container.
80/2 function Equivalent_Elements (Left, Right : Cursor)
return Boolean;
81/2 {AI95-00302-03} Equivalent to Equivalent_Elements (Element (Left),
Element (Right)).
82/2 function Equivalent_Elements (Left : Cursor;
Right : Element_Type) return Boolean;
83/2 {AI95-00302-03} Equivalent to Equivalent_Elements (Element (Left),
Right).
84/2 function Equivalent_Elements (Left : Element_Type;
Right : Cursor) return Boolean;
85/2 {AI95-00302-03} Equivalent to Equivalent_Elements (Left, Element
(Right)).
86/2 {AI95-00302-03} For any element E, the actual function for the generic
formal function Generic_Keys.Hash is expected to be such that Hash (E) =
Generic_Keys.Hash (Key (E)). If the actuals for Key or Generic_Keys.Hash
behave in some other manner, the behavior of Generic_Keys is unspecified.
Which subprograms of Generic_Keys call Generic_Keys.Hash, and how many times
they call it, is unspecified.{unspecified [partial]}
87/2 {AI95-00302-03} For any two elements E1 and E2, the boolean values
Equivalent_Elements (E1, E2) and Equivalent_Keys (Key (E1), Key (E2)) are
expected to be equal. If the actuals for Key or Equivalent_Keys behave in some
other manner, the behavior of Generic_Keys is unspecified. Which subprograms
of Generic_Keys call Equivalent_Keys, and how many times they call it, is
unspecified.{unspecified [partial]}
Implementation Advice
88/2 {AI95-00302-03} If N is the length of a set, the average time complexity
of the subprograms Insert, Include, Replace, Delete, Exclude and Find that
take an element parameter should be O(log N). The average time complexity of
the subprograms that take a cursor parameter should be O(1). The average time
complexity of Reserve_Capacity should be O(N).
88.a/2 Implementation Advice: The average time complexity of the Insert,
Include, Replace, Delete, Exclude and Find operations of
Containers.Hashed_Sets that take an element parameter should be
O(log N). The average time complexity of the subprograms of
Containers.Hashed_Sets that take a cursor parameter should be
O(1). The average time complexity of Containers.Hashed_Sets.-
Reserve_Capacity should be O(N).
88.b/2 Implementation Note: {AI95-00302-03} See A.18.5, "
The Package Containers.Hashed_Maps" for implementation notes
regarding some of the operations of this package.
Extensions to Ada 95
88.c/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Hashed_Sets is new.
A.18.9 The Package Containers.Ordered_Sets
Static Semantics
1/2 {AI95-00302-03} The generic library package Containers.Ordered_Sets has
the following declaration:
2/2 generic
type Element_Type is private;
with function "<" (Left, Right : Element_Type) return Boolean is <>;
with function "=" (Left, Right : Element_Type) return Boolean is <>;
package Ada.Containers.Ordered_Sets is
pragma Preelaborate(Ordered_Sets);
3/2 function Equivalent_Elements
(Left, Right : Element_Type) return Boolean;
4/2 type Set is tagged private;
pragma Preelaborable_Initialization(Set);
5/2 type Cursor is private;
pragma Preelaborable_Initialization(Cursor);
6/2 Empty_Set : constant Set;
7/2 No_Element : constant Cursor;
8/2 function "=" (Left, Right : Set) return Boolean;
9/2 function Equivalent_Sets (Left, Right : Set) return Boolean;
10/2 function To_Set (New_Item : Element_Type) return Set;
11/2 function Length (Container : Set) return Count_Type;
12/2 function Is_Empty (Container : Set) return Boolean;
13/2 procedure Clear (Container : in out Set);
14/2 function Element (Position : Cursor) return Element_Type;
15/2 procedure Replace_Element (Container : in out Set;
Position : in Cursor;
New_Item : in Element_Type);
16/2 procedure Query_Element
(Position : in Cursor;
Process : not null access procedure (Element : in Element_Type));
17/2 procedure Move (Target : in out Set;
Source : in out Set);
18/2 procedure Insert (Container : in out Set;
New_Item : in Element_Type;
Position : out Cursor;
Inserted : out Boolean);
19/2 procedure Insert (Container : in out Set;
New_Item : in Element_Type);
20/2 procedure Include (Container : in out Set;
New_Item : in Element_Type);
21/2 procedure Replace (Container : in out Set;
New_Item : in Element_Type);
22/2 procedure Exclude (Container : in out Set;
Item : in Element_Type);
23/2 procedure Delete (Container : in out Set;
Item : in Element_Type);
24/2 procedure Delete (Container : in out Set;
Position : in out Cursor);
25/2 procedure Delete_First (Container : in out Set);
26/2 procedure Delete_Last (Container : in out Set);
27/2 procedure Union (Target : in out Set;
Source : in Set);
28/2 function Union (Left, Right : Set) return Set;
29/2 function "or" (Left, Right : Set) return Set renames Union;
30/2 procedure Intersection (Target : in out Set;
Source : in Set);
31/2 function Intersection (Left, Right : Set) return Set;
32/2 function "and" (Left, Right : Set) return Set renames Intersection;
33/2 procedure Difference (Target : in out Set;
Source : in Set);
34/2 function Difference (Left, Right : Set) return Set;
35/2 function "-" (Left, Right : Set) return Set renames Difference;
36/2 procedure Symmetric_Difference (Target : in out Set;
Source : in Set);
37/2 function Symmetric_Difference (Left, Right : Set) return Set;
38/2 function "xor" (Left, Right : Set) return Set renames
Symmetric_Difference;
39/2 function Overlap (Left, Right : Set) return Boolean;
40/2 function Is_Subset (Subset : Set;
Of_Set : Set) return Boolean;
41/2 function First (Container : Set) return Cursor;
42/2 function First_Element (Container : Set) return Element_Type;
43/2 function Last (Container : Set) return Cursor;
44/2 function Last_Element (Container : Set) return Element_Type;
45/2 function Next (Position : Cursor) return Cursor;
46/2 procedure Next (Position : in out Cursor);
47/2 function Previous (Position : Cursor) return Cursor;
48/2 procedure Previous (Position : in out Cursor);
49/2 function Find (Container : Set;
Item : Element_Type)
return Cursor;
50/2 function Floor (Container : Set;
Item : Element_Type)
return Cursor;
51/2 function Ceiling (Container : Set;
Item : Element_Type)
return Cursor;
52/2 function Contains (Container : Set;
Item : Element_Type) return Boolean;
53/2 function Has_Element (Position : Cursor) return Boolean;
54/2 function "<" (Left, Right : Cursor) return Boolean;
55/2 function ">" (Left, Right : Cursor) return Boolean;
56/2 function "<" (Left : Cursor; Right : Element_Type)
return Boolean;
57/2 function ">" (Left : Cursor; Right : Element_Type)
return Boolean;
58/2 function "<" (Left : Element_Type; Right : Cursor)
return Boolean;
59/2 function ">" (Left : Element_Type; Right : Cursor)
return Boolean;
60/2 procedure Iterate
(Container : in Set;
Process : not null access procedure (Position : in Cursor));
61/2 procedure Reverse_Iterate
(Container : in Set;
Process : not null access procedure (Position : in Cursor));
62/2 generic
type Key_Type (<>) is private;
with function Key (Element : Element_Type) return Key_Type;
with function "<" (Left, Right : Key_Type)
return Boolean is <>;
package Generic_Keys is
63/2 function Equivalent_Keys (Left, Right : Key_Type)
return Boolean;
64/2 function Key (Position : Cursor) return Key_Type;
65/2 function Element (Container : Set;
Key : Key_Type)
return Element_Type;
66/2 procedure Replace (Container : in out Set;
Key : in Key_Type;
New_Item : in Element_Type);
67/2 procedure Exclude (Container : in out Set;
Key : in Key_Type);
68/2 procedure Delete (Container : in out Set;
Key : in Key_Type);
69/2 function Find (Container : Set;
Key : Key_Type)
return Cursor;
70/2 function Floor (Container : Set;
Key : Key_Type)
return Cursor;
71/2 function Ceiling (Container : Set;
Key : Key_Type)
return Cursor;
72/2 function Contains (Container : Set;
Key : Key_Type) return Boolean;
73/2 procedure Update_Element_Preserving_Key
(Container : in out Set;
Position : in Cursor;
Process : not null access procedure
(Element : in out Element_Type));
74/2 end Generic_Keys;
75/2 private
76/2 ... -- not specified by the language
77/2 end Ada.Containers.Ordered_Sets;
78/2 {AI95-00302-03} Two elements E1 and E2 are equivalent if both E1 < E2 and
E2 < E1 return False, using the generic formal "<" operator for
elements.{equivalent element (of a ordered set)} Function Equivalent_Elements returns
True if Left and Right are equivalent, and False otherwise.
79/2 {AI95-00302-03} The actual function for the generic formal function "<"
on Element_Type values is expected to return the same value each time it is
called with a particular pair of key values. It should define a strict
ordering relationship, that is, be irreflexive, asymmetric, and transitive. If
the actual for "<" behaves in some other manner, the behavior of this package
is unspecified. Which subprograms of this package call "<" and how many times
they call it, is unspecified.{unspecified [partial]}
80/2 {AI95-00302-03} If the value of an element stored in a set is changed
other than by an operation in this package such that at least one of "<" or
"=" give different results, the behavior of this package is
unspecified.{unspecified [partial]}
80.a/2 Discussion: See A.18.6, "The Package Containers.Ordered_Maps" for
a suggested implementation, and for justification of the
restrictions regarding "<" and "=". Note that sets only need to
store elements, not key/element pairs.
81/2 {AI95-00302-03} {first element (of a ordered set)}
{last element (of a ordered set)} {successor element (of a ordered set)} The
first element of a nonempty set is the one which is less than all the other
elements in the set. The last element of a nonempty set is the one which is
greater than all the other elements in the set. The successor of an element is
the smallest element that is larger than the given element. The predecessor of
an element is the largest element that is smaller than the given element. All
comparisons are done using the generic formal "<" operator for elements.
82/2 procedure Delete_First (Container : in out Set);
83/2 {AI95-00302-03} If Container is empty, Delete_First has no effect.
Otherwise the element designated by First (Container) is removed
from Container. Delete_First tampers with the cursors of Container.
84/2 procedure Delete_Last (Container : in out Set);
85/2 {AI95-00302-03} If Container is empty, Delete_Last has no effect.
Otherwise the element designated by Last (Container) is removed
from Container. Delete_Last tampers with the cursors of Container.
86/2 function First_Element (Container : Set) return Element_Type;
87/2 {AI95-00302-03} Equivalent to Element (First (Container)).
88/2 function Last (Container : Set) return Cursor;
89/2 {AI95-00302-03} Returns a cursor that designates the last element
in Container. If Container is empty, returns No_Element.
90/2 function Last_Element (Container : Set) return Element_Type;
91/2 {AI95-00302-03} Equivalent to Element (Last (Container)).
92/2 function Previous (Position : Cursor) return Cursor;
93/2 {AI95-00302-03} If Position equals No_Element, then Previous
returns No_Element. Otherwise Previous returns a cursor
designating the element that precedes the one designated by
Position. If Position designates the first element, then Previous
returns No_Element.
94/2 procedure Previous (Position : in out Cursor);
95/2 {AI95-00302-03} Equivalent to Position := Previous (Position).
96/2 function Floor (Container : Set;
Item : Element_Type) return Cursor;
97/2 {AI95-00302-03} Floor searches for the last element which is not
greater than Item. If such an element is found, a cursor that
designates it is returned. Otherwise No_Element is returned.
98/2 function Ceiling (Container : Set;
Item : Element_Type) return Cursor;
99/2 {AI95-00302-03} Ceiling searches for the first element which is
not less than Item. If such an element is found, a cursor that
designates it is returned. Otherwise No_Element is returned.
100/2 function "<" (Left, Right : Cursor) return Boolean;
101/2 {AI95-00302-03} Equivalent to Element (Left) < Element (Right).
102/2 function ">" (Left, Right : Cursor) return Boolean;
103/2 {AI95-00302-03} Equivalent to Element (Right) < Element (Left).
104/2 function "<" (Left : Cursor; Right : Element_Type) return Boolean;
105/2 {AI95-00302-03} Equivalent to Element (Left) < Right.
106/2 function ">" (Left : Cursor; Right : Element_Type) return Boolean;
107/2 {AI95-00302-03} Equivalent to Right < Element (Left).
108/2 function "<" (Left : Element_Type; Right : Cursor) return Boolean;
109/2 {AI95-00302-03} Equivalent to Left < Element (Right).
110/2 function ">" (Left : Element_Type; Right : Cursor) return Boolean;
111/2 {AI95-00302-03} Equivalent to Element (Right) < Left.
112/2 procedure Reverse_Iterate
(Container : in Set;
Process : not null access procedure (Position : in Cursor));
113/2 {AI95-00302-03} Iterates over the elements in Container as per
Iterate, with the difference that the elements are traversed in
predecessor order, starting with the last element.
114/2 {AI95-00302-03} For any two elements E1 and E2, the boolean values (E1 <
E2) and (Key(E1) < Key(E2)) are expected to be equal. If the actuals for Key
or Generic_Keys."<" behave in some other manner, the behavior of this package
is unspecified. Which subprograms of this package call Key and
Generic_Keys."<", and how many times the functions are called, is
unspecified.{unspecified [partial]}
115/2 {AI95-00302-03} In addition to the semantics described in A.18.7, the
subprograms in package Generic_Keys named Floor and Ceiling, are equivalent to
the corresponding subprograms in the parent package, with the difference that
the Key subprogram parameter is compared to elements in the container using
the Key and "<" generic formal functions. The function named Equivalent_Keys
in package Generic_Keys returns True if both Left < Right and Right < Left
return False using the generic formal "<" operator, and returns True otherwise.
Implementation Advice
116/2 {AI95-00302-03} If N is the length of a set, then the worst-case time
complexity of the Insert, Include, Replace, Delete, Exclude and Find
operations that take an element parameter should be O((log N)**2) or better.
The worst-case time complexity of the subprograms that take a cursor parameter
should be O(1).
116.a/2 Implementation Advice: The worst-case time complexity of the
Insert, Include, Replace, Delete, Exclude and Find operations of
Containers.Ordered_Sets that take an element parameter should be
O((log N)**2). The worst-case time complexity of the subprograms
of Containers.Ordered_Sets that take a cursor parameter should be
O(1).
116.b/2 Implementation Note: {AI95-00302-03} See A.18.6, "
The Package Containers.Ordered_Maps" for implementation notes
regarding some of the operations of this package.
Extensions to Ada 95
116.c/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Ordered_Sets is new.
A.18.10 The Package Containers.Indefinite_Vectors
1/2 {AI95-00302-03} The language-defined generic package
Containers.Indefinite_Vectors provides a private type Vector and a set of
operations. It provides the same operations as the package Containers.Vectors
(see A.18.2), with the difference that the generic formal Element_Type is
indefinite.
Static Semantics
2/2 {AI95-00302-03} The declaration of the generic library package
Containers.Indefinite_Vectors has the same contents as Containers.Vectors
except:
3/2 * The generic formal Element_Type is indefinite.
4/2 * The procedures with the profiles:
5/2 procedure Insert (Container : in out Vector;
Before : in Extended_Index;
Count : in Count_Type := 1);
6 procedure Insert (Container : in out Vector;
Before : in Cursor;
Position : out Cursor;
Count : in Count_Type := 1);
7/2 are omitted.
7.a/2 Discussion: These procedures are omitted because there is no way
to create a default-initialized object of an indefinite type. Note
that Insert_Space can be used instead of this routine in most
cases. Omitting the routine completely allows any problems to be
diagnosed by the compiler when converting from a definite to
indefinite vector.
8/2 * The actual Element parameter of access subprogram Process of
Update_Element may be constrained even if Element_Type is
unconstrained.
Extensions to Ada 95
8.a/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Indefinite_Vectors is new.
A.18.11 The Package Containers.Indefinite_Doubly_Linked_Lists
1/2 {AI95-00302-03} The language-defined generic package
Containers.Indefinite_Doubly_Linked_Lists provides private types List and
Cursor, and a set of operations for each type. It provides the same operations
as the package Containers.Doubly_Linked_Lists (see A.18.3), with the
difference that the generic formal Element_Type is indefinite.
Static Semantics
2/2 {AI95-00302-03} The declaration of the generic library package Containers.-
Indefinite_Doubly_Linked_Lists has the same contents as Containers.Doubly_-
Linked_Lists except:
3/2 * The generic formal Element_Type is indefinite.
4/2 * The procedure with the profile:
5/2 procedure Insert (Container : in out List;
Before : in Cursor;
Position : out Cursor;
Count : in Count_Type := 1);
6/2 is omitted.
6.a/2 Discussion: This procedure is omitted because there is no way to
create a default-initialized object of an indefinite type. We
considered having this routine insert an empty element similar to
the empty elements of a vector, but rejected this possibility
because the semantics are fairly complex and very different from
the existing case. That would make it more error-prone to convert
a container from a definite type to an indefinite type; by
omitting the routine completely, any problems will be diagnosed by
the compiler.
7/2 * The actual Element parameter of access subprogram Process of
Update_Element may be constrained even if Element_Type is
unconstrained.
Extensions to Ada 95
7.a/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Indefinite_Doubly_Linked_Lists is new.
A.18.12 The Package Containers.Indefinite_Hashed_Maps
1/2 {AI95-00302-03} The language-defined generic package
Containers.Indefinite_Hashed_Maps provides a map with the same operations as
the package Containers.Hashed_Maps (see A.18.5), with the difference that the
generic formal types Key_Type and Element_Type are indefinite.
Static Semantics
2/2 {AI95-00302-03} The declaration of the generic library package
Containers.Indefinite_Hashed_Maps has the same contents as
Containers.Hashed_Maps except:
3/2 * The generic formal Key_Type is indefinite.
4/2 * The generic formal Element_Type is indefinite.
5/2 * The procedure with the profile:
6/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
Position : out Cursor;
Inserted : out Boolean);
7/2 is omitted.
7.a/2 Discussion: This procedure is omitted because there is no way to
create a default-initialized object of an indefinite type. We
considered having this routine insert an empty element similar to
the empty elements of a vector, but rejected this possibility
because the semantics are fairly complex and very different from
the existing case. That would make it more error-prone to convert
a container from a definite type to an indefinite type; by
omitting the routine completely, any problems will be diagnosed by
the compiler.
8/2 * The actual Element parameter of access subprogram Process of
Update_Element may be constrained even if Element_Type is
unconstrained.
Extensions to Ada 95
8.a/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Indefinite_Hashed_Maps is new.
A.18.13 The Package Containers.Indefinite_Ordered_Maps
1/2 {AI95-00302-03} The language-defined generic package
Containers.Indefinite_Ordered_Maps provides a map with the same operations as
the package Containers.Ordered_Maps (see A.18.6), with the difference that the
generic formal types Key_Type and Element_Type are indefinite.
Static Semantics
2/2 {AI95-00302-03} The declaration of the generic library package
Containers.Indefinite_Ordered_Maps has the same contents as
Containers.Ordered_Maps except:
3/2 * The generic formal Key_Type is indefinite.
4/2 * The generic formal Element_Type is indefinite.
5/2 * The procedure with the profile:
6/2 procedure Insert (Container : in out Map;
Key : in Key_Type;
Position : out Cursor;
Inserted : out Boolean);
7/2 is omitted.
7.a/2 Discussion: This procedure is omitted because there is no way to
create a default-initialized object of an indefinite type. We
considered having this routine insert an empty element similar to
the empty elements of a vector, but rejected this possibility
because the semantics are fairly complex and very different from
the existing case. That would make it more error-prone to convert
a container from a definite type to an indefinite type; by
omitting the routine completely, any problems will be diagnosed by
the compiler.
8/2 * The actual Element parameter of access subprogram Process of
Update_Element may be constrained even if Element_Type is
unconstrained.
Extensions to Ada 95
8.a/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Indefinite_Ordered_Maps is new.
A.18.14 The Package Containers.Indefinite_Hashed_Sets
1/2 {AI95-00302-03} The language-defined generic package
Containers.Indefinite_Hashed_Sets provides a set with the same operations as
the package Containers.Hashed_Sets (see A.18.8), with the difference that the
generic formal type Element_Type is indefinite.
Static Semantics
2/2 {AI95-00302-03} The declaration of the generic library package
Containers.Indefinite_Hashed_Sets has the same contents as
Containers.Hashed_Sets except:
3/2 * The generic formal Element_Type is indefinite.
4/2 * The actual Element parameter of access subprogram Process of Update_-
Element_Preserving_Key may be constrained even if Element_Type is
unconstrained.
Extensions to Ada 95
4.a/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Indefinite_Hashed_Sets is new.
A.18.15 The Package Containers.Indefinite_Ordered_Sets
1/2 {AI95-00302-03} The language-defined generic package
Containers.Indefinite_Ordered_Sets provides a set with the same operations as
the package Containers.Ordered_Sets (see A.18.9), with the difference that the
generic formal type Element_Type is indefinite.
Static Semantics
2/2 {AI95-00302-03} The declaration of the generic library package
Containers.Indefinite_Ordered_Sets has the same contents as
Containers.Ordered_Sets except:
3/2 * The generic formal Element_Type is indefinite.
4/2 * The actual Element parameter of access subprogram Process of Update_-
Element_Preserving_Key may be constrained even if Element_Type is
unconstrained.
Extensions to Ada 95
4.a/2 {AI95-00302-03} {extensions to Ada 95} The generic package
Containers.Indefinite_Ordered_Sets is new.
A.18.16 Array Sorting
1/2 {AI95-00302-03} The language-defined generic procedures
Containers.Generic_Array_Sort and Containers.Generic_Constrained_Array_Sort
provide sorting on arbitrary array types.
Static Semantics
2/2 {AI95-00302-03} The generic library procedure
Containers.Generic_Array_Sort has the following declaration:
3/2 generic
type Index_Type is (<>);
type Element_Type is private;
type Array_Type is array (Index_Type range <>) of Element_Type;
with function "<" (Left, Right : Element_Type)
return Boolean is <>;
procedure Ada.Containers.Generic_Array_Sort (Container : in out Array_Type);
pragma Pure(Ada.Containers.Generic_Array_Sort);
4/2 Reorders the elements of Container such that the elements are
sorted smallest first as determined by the generic formal "<"
operator provided. Any exception raised during evaluation of "<"
is propagated.
5/2 The actual function for the generic formal function "<" of
Generic_Array_Sort is expected to return the same value each time
it is called with a particular pair of element values. It should
define a strict ordering relationship, that is, be irreflexive,
asymmetric, and transitive; it should not modify Container. If the
actual for "<" behaves in some other manner, the behavior of the
instance of Generic_Array_Sort is unspecified. How many times
Generic_Array_Sort calls "<" is unspecified.{unspecified
[partial]}
5.a/2 Ramification: This implies swapping the elements, usually
including an intermediate copy. This of course means that the
elements will be copied. Since the elements are nonlimited, this
usually will not be a problem. Note that there is Implementation
Advice below that the implementation should use a sort that
minimizes copying of elements.
5.b/2 The sort is not required to be stable (and the fast algorithm
required will not be stable). If a stable sort is needed, the user
can include the original location of the element as an extra "sort
key". We considered requiring the implementation to do that, but
it is mostly extra overhead -- usually there is something already
in the element that provides the needed stability.
6/2 {AI95-00302-03} The generic library procedure
Containers.Generic_Constrained_Array_Sort has the following declaration:
7/2 generic
type Index_Type is (<>);
type Element_Type is private;
type Array_Type is array (Index_Type) of Element_Type;
with function "<" (Left, Right : Element_Type)
return Boolean is <>;
procedure Ada.Containers.Generic_Constrained_Array_Sort
(Container : in out Array_Type);
pragma Pure(Ada.Containers.Generic_Constrained_Array_Sort);
8/2 Reorders the elements of Container such that the elements are
sorted smallest first as determined by the generic formal "<"
operator provided. Any exception raised during evaluation of "<"
is propagated.
9/2 The actual function for the generic formal function "<" of
Generic_Constrained_Array_Sort is expected to return the same
value each time it is called with a particular pair of element
values. It should define a strict ordering relationship, that is,
be irreflexive, asymmetric, and transitive; it should not modify
Container. If the actual for "<" behaves in some other manner, the
behavior of the instance of Generic_Constrained_Array_Sort is
unspecified. How many times Generic_Constrained_Array_Sort calls
"<" is unspecified.{unspecified [partial]}
Implementation Advice
10/2 {AI95-00302-03} The worst-case time complexity of a call on an instance
of Containers.Generic_Array_Sort or Containers.Generic_Constrained_Array_Sort
should be O(N**2) or better, and the average time complexity should be better
than O(N**2), where N is the length of the Container parameter.
10.a/2 Implementation Advice: Containers.Generic_Array_Sort and
Containers.Generic_Constrained_Array_Sort should have an average
time complexity better than O(N**2) and worst case no worse than
O(N**2).
10.b/2 Discussion: In other words, we're requiring the use of a sorting
algorithm better than O(N**2), such as Quicksort. No bubble sorts
allowed!
11/2 {AI95-00302-03} Containers.Generic_Array_Sort and
Containers.Generic_Constrained_Array_Sort should minimize copying of elements.
11.a/2 Implementation Advice: Containers.Generic_Array_Sort and
Containers.Generic_Constrained_Array_Sort should minimize copying
of elements.
11.b/2 To be honest: We do not mean "absolutely minimize" here; we're not
intending to require a single copy for each element. Rather, we
want to suggest that the sorting algorithm chosen is one that does
not copy items unnecessarily. Bubble sort would not meet this
advice, for instance.
Extensions to Ada 95
11.c/2 {AI95-00302-03} {extensions to Ada 95} The generic packages
Containers.Generic_Array_Sort and
Containers.Generic_Constrained_Array_Sort are new.
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