Annex N
(informative)
Glossary
1/2 {AI95-00437-01} {Glossary} This Annex contains informal descriptions of
some of the terms used in this International Standard. The index provides
references to more formal definitions of all of the terms used in this
International Standard.
1.1/2 {abstract type} Abstract type. An abstract type is a tagged type
intended for use as an ancestor of other types, but which is not allowed to
have objects of its own.
2 {access type} Access type. An access type has values that designate
aliased objects. Access types correspond to "pointer types" or "reference
types" in some other languages.
3 {aliased} Aliased. An aliased view of an object is one that can be
designated by an access value. Objects allocated by allocators are aliased.
Objects can also be explicitly declared as aliased with the reserved word
aliased. The Access attribute can be used to create an access value
designating an aliased object.
3.1/2 {ancestor} Ancestor. An ancestor of a type is the type itself or, in the
case of a type derived from other types, its parent type or one of its
progenitor types or one of their ancestors. Note that ancestor and descendant
are inverse relationships.
4 {array type} Array type. An array type is a composite type whose
components are all of the same type. Components are selected by indexing.
4.1/2 {category (of types)} Category (of types). A category of types is a set
of types with one or more common properties, such as primitive operations. A
category of types that is closed under derivation is also known as a class.
5 {character type} Character type. A character type is an enumeration type
whose values include characters.
6/2 {class (of types)} Class (of types). {closed under derivation} A class is
a set of types that is closed under derivation, which means that if a given
type is in the class, then all types derived from that type are also in the
class. The set of types of a class share common properties, such as their
primitive operations.
7 {compilation unit} Compilation unit. The text of a program can be
submitted to the compiler in one or more compilations. Each compilation is a
succession of compilation_units. A compilation_unit contains either the
declaration, the body, or a renaming of a program unit.
8/2 {composite type} Composite type. A composite type may have components.
9 {construct} Construct. A construct is a piece of text (explicit or
implicit) that is an instance of a syntactic category defined under "Syntax
".
10 {controlled type} Controlled type. A controlled type supports user-defined
assignment and finalization. Objects are always finalized before being
destroyed.
11 {declaration} Declaration. A declaration is a language construct that
associates a name with (a view of) an entity. {explicit declaration}
{implicit declaration} A declaration may appear explicitly in the program text
(an explicit declaration), or may be supposed to occur at a given place in the
text as a consequence of the semantics of another construct (an implicit
declaration).
12/2 This paragraph was deleted.
13/2 {derived type} Derived type. A derived type is a type defined in terms of
one or more other types given in a derived type definition. The first of those
types is the parent type of the derived type and any others are progenitor
types. Each class containing the parent type or a progenitor type also
contains the derived type. The derived type inherits properties such as
components and primitive operations from the parent and progenitors. A type
together with the types derived from it (directly or indirectly) form a
derivation class.
13.1/2 {descendant} Descendant. A type is a descendant of itself, its parent
and progenitor types, and their ancestors. Note that descendant and ancestor
are inverse relationships.
14 {discrete type} Discrete type. A discrete type is either an integer type
or an enumeration type. Discrete types may be used, for example, in
case_statements and as array indices.
15/2 {discriminant} Discriminant. A discriminant is a parameter for a
composite type. It can control, for example, the bounds of a component of the
type if the component is an array. A discriminant for a task type can be used
to pass data to a task of the type upon creation.
15.1/2 {elaboration} Elaboration. The process by which a declaration achieves
its run-time effect is called elaboration. Elaboration is one of the forms of
execution.
16 {elementary type} Elementary type. An elementary type does not have
components.
17 {enumeration type} Enumeration type. An enumeration type is defined by an
enumeration of its values, which may be named by identifiers or character
literals.
17.1/2 {evaluation} Evaluation. The process by which an expression achieves
its run-time effect is called evaluation. Evaluation is one of the forms of
execution.
18 {exception} Exception. An exception represents a kind of exceptional
situation; an occurrence of such a situation (at run time) is called an
exception occurrence. {raise (an exception) [partial]} To raise an exception
is to abandon normal program execution so as to draw attention to the fact
that the corresponding situation has arisen. {handle (an exception)
[partial]} Performing some actions in response to the arising of an exception
is called handling the exception.
19 {execution} Execution. The process by which a construct achieves its
run-time effect is called execution. {elaboration} {evaluation} Execution of a
declaration is also called elaboration. Execution of an expression is also
called evaluation.
19.1/2 {function} Function. A function is a form of subprogram that returns a
result and can be called as part of an expression.
20 {generic unit} Generic unit. A generic unit is a template for a
(nongeneric) program unit; the template can be parameterized by objects,
types, subprograms, and packages. An instance of a generic unit is created by
a generic_instantiation. The rules of the language are enforced when a generic
unit is compiled, using a generic contract model; additional checks are
performed upon instantiation to verify the contract is met. That is, the
declaration of a generic unit represents a contract between the body of the
generic and instances of the generic. Generic units can be used to perform the
role that macros sometimes play in other languages.
20.1/2 {incomplete type} Incomplete type. An incomplete type gives a view of a
type that reveals only some of its properties. The remaining properties are
provided by the full view given elsewhere. Incomplete types can be used for
defining recursive data structures.
21 {integer type} Integer type. Integer types comprise the signed integer
types and the modular types. A signed integer type has a base range that
includes both positive and negative numbers, and has operations that may raise
an exception when the result is outside the base range. A modular type has a
base range whose lower bound is zero, and has operations with "wraparound"
semantics. Modular types subsume what are called "unsigned types" in some
other languages.
21.1/2 {interface type} Interface type. An interface type is a form of
abstract tagged type which has no components or concrete operations except
possibly null procedures. Interface types are used for composing other
interfaces and tagged types and thereby provide multiple inheritance. Only an
interface type can be used as a progenitor of another type.
22 {library unit} Library unit. A library unit is a separately compiled
program unit, and is always a package, subprogram, or generic unit. Library
units may have other (logically nested) library units as children, and may
have other program units physically nested within them. {subsystem} A root
library unit, together with its children and grandchildren and so on, form a
subsystem.
23/2 {limited type} Limited type. A limited type is a type for which copying
(such as in an assignment_statement) is not allowed. A nonlimited type is a
type for which copying is allowed.
24 {object} Object. An object is either a constant or a variable. An object
contains a value. An object is created by an object_declaration or by an
allocator. A formal parameter is (a view of) an object. A subcomponent of an
object is an object.
24.1/2 {overriding operation} Overriding operation. An overriding operation is
one that replaces an inherited primitive operation. Operations may be marked
explicitly as overriding or not overriding.
25 {package} Package. Packages are program units that allow the specification
of groups of logically related entities. Typically, a package contains the
declaration of a type (often a private type or private extension) along with
the declarations of primitive subprograms of the type, which can be called
from outside the package, while their inner workings remain hidden from
outside users.
25.1/2 {parent} Parent. The parent of a derived type is the first type given
in the definition of the derived type. The parent can be almost any kind of
type, including an interface type.
26 {partition} Partition. A partition is a part of a program. Each partition
consists of a set of library units. Each partition may run in a separate
address space, possibly on a separate computer. A program may contain just one
partition. A distributed program typically contains multiple partitions, which
can execute concurrently.
27 {pragma} Pragma. A pragma is a compiler directive. There are
language-defined pragmas that give instructions for optimization, listing
control, etc. An implementation may support additional
(implementation-defined) pragmas.
28 {primitive operations} Primitive operations. The primitive operations of a
type are the operations (such as subprograms) declared together with the type
declaration. They are inherited by other types in the same class of types. For
a tagged type, the primitive subprograms are dispatching subprograms,
providing run-time polymorphism. A dispatching subprogram may be called with
statically tagged operands, in which case the subprogram body invoked is
determined at compile time. Alternatively, a dispatching subprogram may be
called using a dispatching call, in which case the subprogram body invoked is
determined at run time.
29/2 {private extension} Private extension. A private extension is a type that
extends another type, with the additional properties hidden from its clients.
30/2 {private type} Private type. A private type gives a view of a type that
reveals only some of its properties. The remaining properties are provided by
the full view given elsewhere. Private types can be used for defining
abstractions that hide unnecessary details from their clients.
30.1/2 {procedure} Procedure. A procedure is a form of subprogram that does
not return a result and can only be called by a statement.
30.2/2 {progenitor} Progenitor. A progenitor of a derived type is one of the
types given in the definition of the derived type other than the first. A
progenitor is always an interface type. Interfaces, tasks, and protected types
may also have progenitors.
31 {program} Program. A program is a set of partitions, each of which may
execute in a separate address space, possibly on a separate computer. A
partition consists of a set of library units.
32 {program unit} Program unit. A program unit is either a package, a task
unit, a protected unit, a protected entry, a generic unit, or an explicitly
declared subprogram other than an enumeration literal. Certain kinds of
program units can be separately compiled. Alternatively, they can appear
physically nested within other program units.
33/2 {protected type} Protected type. A protected type is a composite type
whose components are accessible only through one of its protected operations
which synchronize concurrent access by multiple tasks.
34 {real type} Real type. A real type has values that are approximations of
the real numbers. Floating point and fixed point types are real types.
35 {record extension} Record extension. A record extension is a type that
extends another type by adding additional components.
36 {record type} Record type. A record type is a composite type consisting of
zero or more named components, possibly of different types.
36.1/2 {renaming} Renaming. A renaming_declaration is a declaration that does
not define a new entity, but instead defines a view of an existing entity.
37 {scalar type} Scalar type. A scalar type is either a discrete type or a
real type.
37.1/2 {subprogram} Subprogram. A subprogram is a section of a program that
can be executed in various contexts. It is invoked by a subprogram call that
may qualify the effect of the subprogram through the passing of parameters.
There are two forms of subprograms: functions, which return values, and
procedures, which do not.
38/2 {subtype} Subtype. A subtype is a type together with a constraint or null
exclusion, which constrains the values of the subtype to satisfy a certain
condition. The values of a subtype are a subset of the values of its type.
38.1/2 {synchronized} Synchronized. A synchronized entity is one that will
work safely with multiple tasks at one time. A synchronized interface can be
an ancestor of a task or a protected type. Such a task or protected type is
called a synchronized tagged type.
39 {tagged type} Tagged type. The objects of a tagged type have a run-time
type tag, which indicates the specific type with which the object was
originally created. An operand of a class-wide tagged type can be used in a
dispatching call; the tag indicates which subprogram body to invoke.
Nondispatching calls, in which the subprogram body to invoke is determined at
compile time, are also allowed. Tagged types may be extended with additional
components.
40/2 {task type} Task type. A task type is a composite type used to represent
active entities which execute concurrently and which can communicate via
queued task entries. The top-level task of a partition is called the
environment task.
41/2 {type} Type. Each object has a type. A type has an associated set of
values, and a set of primitive operations which implement the fundamental
aspects of its semantics. Types are grouped into categories. Most
language-defined categories of types are also classes of types.
42/2 {view} View. A view of an entity reveals some or all of the properties of
the entity. A single entity may have multiple views.
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