Stdlib(3o) OCaml library Stdlib(3o)
NAME
Stdlib - The OCaml Standard library.
Module
Module Stdlib
Documentation
Module Stdlib
: sig end
The OCaml Standard library.
This module is automatically opened at the beginning of each compila-
tion. All components of this module can therefore be referred by their
short name, without prefixing them by Stdlib .
It particular, it provides the basic operations over the built-in types
(numbers, booleans, byte sequences, strings, exceptions, references,
lists, arrays, input-output channels, ...) and the modules .
Exceptions
val raise : exn -> 'a
Raise the given exception value
val raise_notrace : exn -> 'a
A faster version raise which does not record the backtrace.
Since 4.02.0
val invalid_arg : string -> 'a
Raise exception Invalid_argument with the given string.
val failwith : string -> 'a
Raise exception Failure with the given string.
exception Exit
The Exit exception is not raised by any library function. It is pro-
vided for use in your programs.
exception Match_failure of (string * int * int)
Exception raised when none of the cases of a pattern-matching apply.
The arguments are the location of the match keyword in the source code
(file name, line number, column number).
exception Assert_failure of (string * int * int)
Exception raised when an assertion fails. The arguments are the loca-
tion of the assert keyword in the source code (file name, line number,
column number).
exception Invalid_argument of string
Exception raised by library functions to signal that the given argu-
ments do not make sense. The string gives some information to the pro-
grammer. As a general rule, this exception should not be caught, it de-
notes a programming error and the code should be modified not to trig-
ger it.
exception Failure of string
Exception raised by library functions to signal that they are undefined
on the given arguments. The string is meant to give some information to
the programmer; you must not pattern match on the string literal be-
cause it may change in future versions (use Failure _ instead).
exception Not_found
Exception raised by search functions when the desired object could not
be found.
exception Out_of_memory
Exception raised by the garbage collector when there is insufficient
memory to complete the computation. (Not reliable for allocations on
the minor heap.)
exception Stack_overflow
Exception raised by the bytecode interpreter when the evaluation stack
reaches its maximal size. This often indicates infinite or excessively
deep recursion in the user's program.
Before 4.10, it was not fully implemented by the native-code compiler.
exception Sys_error of string
Exception raised by the input/output functions to report an operating
system error. The string is meant to give some information to the pro-
grammer; you must not pattern match on the string literal because it
may change in future versions (use Sys_error _ instead).
exception End_of_file
Exception raised by input functions to signal that the end of file has
been reached.
exception Division_by_zero
Exception raised by integer division and remainder operations when
their second argument is zero.
exception Sys_blocked_io
A special case of Sys_error raised when no I/O is possible on a
non-blocking I/O channel.
exception Undefined_recursive_module of (string * int * int)
Exception raised when an ill-founded recursive module definition is
evaluated. The arguments are the location of the definition in the
source code (file name, line number, column number).
Comparisons
val (=) : 'a -> 'a -> bool
e1 = e2 tests for structural equality of e1 and e2 . Mutable struc-
tures (e.g. references and arrays) are equal if and only if their cur-
rent contents are structurally equal, even if the two mutable objects
are not the same physical object. Equality between functional values
raises Invalid_argument . Equality between cyclic data structures may
not terminate. Left-associative operator, see Ocaml_operators for more
information.
val (<>) : 'a -> 'a -> bool
Negation of (=) . Left-associative operator, see Ocaml_operators for
more information.
val (<) : 'a -> 'a -> bool
See (>=) . Left-associative operator, see Ocaml_operators for more in-
formation.
val (>) : 'a -> 'a -> bool
See (>=) . Left-associative operator, see Ocaml_operators for more
information.
val (<=) : 'a -> 'a -> bool
See (>=) . Left-associative operator, see Ocaml_operators for more
information.
val (>=) : 'a -> 'a -> bool
Structural ordering functions. These functions coincide with the usual
orderings over integers, characters, strings, byte sequences and float-
ing-point numbers, and extend them to a total ordering over all types.
The ordering is compatible with ( = ) . As in the case of ( = ) , muta-
ble structures are compared by contents. Comparison between functional
values raises Invalid_argument . Comparison between cyclic structures
may not terminate. Left-associative operator, see Ocaml_operators for
more information.
val compare : 'a -> 'a -> int
compare x y returns 0 if x is equal to y , a negative integer if x is
less than y , and a positive integer if x is greater than y . The or-
dering implemented by compare is compatible with the comparison predi-
cates = , < and > defined above, with one difference on the treatment
of the float value nan . Namely, the comparison predicates treat nan
as different from any other float value, including itself; while com-
pare treats nan as equal to itself and less than any other float value.
This treatment of nan ensures that compare defines a total ordering re-
lation.
compare applied to functional values may raise Invalid_argument . com-
pare applied to cyclic structures may not terminate.
The compare function can be used as the comparison function required by
the Set.Make and Map.Make functors, as well as the List.sort and Ar-
ray.sort functions.
val min : 'a -> 'a -> 'a
Return the smaller of the two arguments. The result is unspecified if
one of the arguments contains the float value nan .
val max : 'a -> 'a -> 'a
Return the greater of the two arguments. The result is unspecified if
one of the arguments contains the float value nan .
val (==) : 'a -> 'a -> bool
e1 == e2 tests for physical equality of e1 and e2 . On mutable types
such as references, arrays, byte sequences, records with mutable fields
and objects with mutable instance variables, e1 == e2 is true if and
only if physical modification of e1 also affects e2 . On non-mutable
types, the behavior of ( == ) is implementation-dependent; however, it
is guaranteed that e1 == e2 implies compare e1 e2 = 0 . Left-associa-
tive operator, see Ocaml_operators for more information.
val (!=) : 'a -> 'a -> bool
Negation of (==) . Left-associative operator, see Ocaml_operators for
more information.
Boolean operations
val not : bool -> bool
The boolean negation.
val (&&) : bool -> bool -> bool
The boolean 'and'. Evaluation is sequential, left-to-right: in e1 && e2
, e1 is evaluated first, and if it returns false , e2 is not evaluated
at all. Right-associative operator, see Ocaml_operators for more in-
formation.
val (&) : bool -> bool -> bool
Deprecated.
(&&) should be used instead. Right-associative operator, see Ocaml_op-
erators for more information.
val (||) : bool -> bool -> bool
The boolean 'or'. Evaluation is sequential, left-to-right: in e1 || e2
, e1 is evaluated first, and if it returns true , e2 is not evaluated
at all. Right-associative operator, see Ocaml_operators for more in-
formation.
val (or) : bool -> bool -> bool
Deprecated.
(||) should be used instead. Right-associative operator, see Ocaml_op-
erators for more information.
Debugging
val __LOC__ : string
__LOC__ returns the location at which this expression appears in the
file currently being parsed by the compiler, with the standard error
format of OCaml: "File %S, line %d, characters %d-%d".
Since 4.02.0
val __FILE__ : string
__FILE__ returns the name of the file currently being parsed by the
compiler.
Since 4.02.0
val __LINE__ : int
__LINE__ returns the line number at which this expression appears in
the file currently being parsed by the compiler.
Since 4.02.0
val __MODULE__ : string
__MODULE__ returns the module name of the file being parsed by the com-
piler.
Since 4.02.0
val __POS__ : string * int * int * int
__POS__ returns a tuple (file,lnum,cnum,enum) , corresponding to the
location at which this expression appears in the file currently being
parsed by the compiler. file is the current filename, lnum the line
number, cnum the character position in the line and enum the last char-
acter position in the line.
Since 4.02.0
val __FUNCTION__ : string
__FUNCTION__ returns the name of the current function or method, in-
cluding any enclosing modules or classes.
Since 4.12.0
val __LOC_OF__ : 'a -> string * 'a
__LOC_OF__ expr returns a pair (loc, expr) where loc is the location of
expr in the file currently being parsed by the compiler, with the stan-
dard error format of OCaml: "File %S, line %d, characters %d-%d".
Since 4.02.0
val __LINE_OF__ : 'a -> int * 'a
__LINE_OF__ expr returns a pair (line, expr) , where line is the line
number at which the expression expr appears in the file currently being
parsed by the compiler.
Since 4.02.0
val __POS_OF__ : 'a -> (string * int * int * int) * 'a
__POS_OF__ expr returns a pair (loc,expr) , where loc is a tuple
(file,lnum,cnum,enum) corresponding to the location at which the ex-
pression expr appears in the file currently being parsed by the com-
piler. file is the current filename, lnum the line number, cnum the
character position in the line and enum the last character position in
the line.
Since 4.02.0
Composition operators
val (|>) : 'a -> ('a -> 'b) -> 'b
Reverse-application operator: x |> f |> g is exactly equivalent to g (f
(x)) . Left-associative operator, see Ocaml_operators for more infor-
mation.
Since 4.01
val (@@) : ('a -> 'b) -> 'a -> 'b
Application operator: g @@ f @@ x is exactly equivalent to g (f (x)) .
Right-associative operator, see Ocaml_operators for more information.
Since 4.01
Integer arithmetic
Integers are Sys.int_size bits wide. All operations are taken modulo
2^ Sys.int_size . They do not fail on overflow.
val (~-) : int -> int
Unary negation. You can also write - e instead of ~- e . Unary opera-
tor, see Ocaml_operators for more information.
val (~+) : int -> int
Unary addition. You can also write + e instead of ~+ e . Unary opera-
tor, see Ocaml_operators for more information.
Since 3.12.0
val succ : int -> int
succ x is x + 1 .
val pred : int -> int
pred x is x - 1 .
val (+) : int -> int -> int
Integer addition. Left-associative operator, see Ocaml_operators for
more information.
val (-) : int -> int -> int
Integer subtraction. Left-associative operator, , see Ocaml_operators
for more information.
val ( * ) : int -> int -> int
Integer multiplication. Left-associative operator, see Ocaml_operators
for more information.
val (/) : int -> int -> int
Integer division. Integer division rounds the real quotient of its ar-
guments towards zero. More precisely, if x >= 0 and y > 0 , x / y is
the greatest integer less than or equal to the real quotient of x by y
. Moreover, (- x) / y = x / (- y) = - (x / y) . Left-associative op-
erator, see Ocaml_operators for more information.
Raises Division_by_zero if the second argument is 0.
val (mod) : int -> int -> int
Integer remainder. If y is not zero, the result of x mod y satisfies
the following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
abs(y) - 1 . If y = 0 , x mod y raises Division_by_zero . Note that x
mod y is negative only if x < 0 . Left-associative operator, see
Ocaml_operators for more information.
Raises Division_by_zero if y is zero.
val abs : int -> int
Return the absolute value of the argument. Note that this may be nega-
tive if the argument is min_int .
val max_int : int
The greatest representable integer.
val min_int : int
The smallest representable integer.
Bitwise operations
val (land) : int -> int -> int
Bitwise logical and. Left-associative operator, see Ocaml_operators
for more information.
val (lor) : int -> int -> int
Bitwise logical or. Left-associative operator, see Ocaml_operators for
more information.
val (lxor) : int -> int -> int
Bitwise logical exclusive or. Left-associative operator, see Ocaml_op-
erators for more information.
val lnot : int -> int
Bitwise logical negation.
val (lsl) : int -> int -> int
n lsl m shifts n to the left by m bits. The result is unspecified if m
< 0 or m > Sys.int_size . Right-associative operator, see Ocaml_opera-
tors for more information.
val (lsr) : int -> int -> int
n lsr m shifts n to the right by m bits. This is a logical shift: ze-
roes are inserted regardless of the sign of n . The result is unspeci-
fied if m < 0 or m > Sys.int_size . Right-associative operator, see
Ocaml_operators for more information.
val (asr) : int -> int -> int
n asr m shifts n to the right by m bits. This is an arithmetic shift:
the sign bit of n is replicated. The result is unspecified if m < 0 or
m > Sys.int_size . Right-associative operator, see Ocaml_operators for
more information.
Floating-point arithmetic
OCaml's floating-point numbers follow the IEEE 754 standard, using dou-
ble precision (64 bits) numbers. Floating-point operations never raise
an exception on overflow, underflow, division by zero, etc. Instead,
special IEEE numbers are returned as appropriate, such as infinity for
1.0 /. 0.0 , neg_infinity for -1.0 /. 0.0 , and nan ('not a number')
for 0.0 /. 0.0 . These special numbers then propagate through float-
ing-point computations as expected: for instance, 1.0 /. infinity is
0.0 , basic arithmetic operations ( +. , -. , *. , /. ) with nan as
an argument return nan , ...
val (~-.) : float -> float
Unary negation. You can also write -. e instead of ~-. e . Unary oper-
ator, see Ocaml_operators for more information.
val (~+.) : float -> float
Unary addition. You can also write +. e instead of ~+. e . Unary oper-
ator, see Ocaml_operators for more information.
Since 3.12.0
val (+.) : float -> float -> float
Floating-point addition. Left-associative operator, see Ocaml_opera-
tors for more information.
val (-.) : float -> float -> float
Floating-point subtraction. Left-associative operator, see Ocaml_oper-
ators for more information.
val ( *. ) : float -> float -> float
Floating-point multiplication. Left-associative operator, see
Ocaml_operators for more information.
val (/.) : float -> float -> float
Floating-point division. Left-associative operator, see Ocaml_opera-
tors for more information.
val ( ** ) : float -> float -> float
Exponentiation. Right-associative operator, see Ocaml_operators for
more information.
val sqrt : float -> float
Square root.
val exp : float -> float
Exponential.
val log : float -> float
Natural logarithm.
val log10 : float -> float
Base 10 logarithm.
val expm1 : float -> float
expm1 x computes exp x -. 1.0 , giving numerically-accurate results
even if x is close to 0.0 .
Since 3.12.0
val log1p : float -> float
log1p x computes log(1.0 +. x) (natural logarithm), giving numeri-
cally-accurate results even if x is close to 0.0 .
Since 3.12.0
val cos : float -> float
Cosine. Argument is in radians.
val sin : float -> float
Sine. Argument is in radians.
val tan : float -> float
Tangent. Argument is in radians.
val acos : float -> float
Arc cosine. The argument must fall within the range [-1.0, 1.0] . Re-
sult is in radians and is between 0.0 and pi .
val asin : float -> float
Arc sine. The argument must fall within the range [-1.0, 1.0] . Re-
sult is in radians and is between -pi/2 and pi/2 .
val atan : float -> float
Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
val atan2 : float -> float -> float
atan2 y x returns the arc tangent of y /. x . The signs of x and y are
used to determine the quadrant of the result. Result is in radians and
is between -pi and pi .
val hypot : float -> float -> float
hypot x y returns sqrt(x *. x + y *. y) , that is, the length of the
hypotenuse of a right-angled triangle with sides of length x and y ,
or, equivalently, the distance of the point (x,y) to origin. If one of
x or y is infinite, returns infinity even if the other is nan .
Since 4.00.0
val cosh : float -> float
Hyperbolic cosine. Argument is in radians.
val sinh : float -> float
Hyperbolic sine. Argument is in radians.
val tanh : float -> float
Hyperbolic tangent. Argument is in radians.
val acosh : float -> float
Hyperbolic arc cosine. The argument must fall within the range [1.0,
inf] . Result is in radians and is between 0.0 and inf .
Since 4.13.0
val asinh : float -> float
Hyperbolic arc sine. The argument and result range over the entire
real line. Result is in radians.
Since 4.13.0
val atanh : float -> float
Hyperbolic arc tangent. The argument must fall within the range [-1.0,
1.0] . Result is in radians and ranges over the entire real line.
Since 4.13.0
val ceil : float -> float
Round above to an integer value. ceil f returns the least integer
value greater than or equal to f . The result is returned as a float.
val floor : float -> float
Round below to an integer value. floor f returns the greatest integer
value less than or equal to f . The result is returned as a float.
val abs_float : float -> float
abs_float f returns the absolute value of f .
val copysign : float -> float -> float
copysign x y returns a float whose absolute value is that of x and
whose sign is that of y . If x is nan , returns nan . If y is nan ,
returns either x or -. x , but it is not specified which.
Since 4.00.0
val mod_float : float -> float -> float
mod_float a b returns the remainder of a with respect to b . The re-
turned value is a -. n *. b , where n is the quotient a /. b rounded
towards zero to an integer.
val frexp : float -> float * int
frexp f returns the pair of the significant and the exponent of f .
When f is zero, the significant x and the exponent n of f are equal to
zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
<= x < 1.0 .
val ldexp : float -> int -> float
ldexp x n returns x *. 2 ** n .
val modf : float -> float * float
modf f returns the pair of the fractional and integral part of f .
val float : int -> float
Same as float_of_int .
val float_of_int : int -> float
Convert an integer to floating-point.
val truncate : float -> int
Same as int_of_float .
val int_of_float : float -> int
Truncate the given floating-point number to an integer. The result is
unspecified if the argument is nan or falls outside the range of repre-
sentable integers.
val infinity : float
Positive infinity.
val neg_infinity : float
Negative infinity.
val nan : float
A special floating-point value denoting the result of an undefined op-
eration such as 0.0 /. 0.0 . Stands for 'not a number'. Any float-
ing-point operation with nan as argument returns nan as result. As for
floating-point comparisons, = , < , <= , > and >= return false and <>
returns true if one or both of their arguments is nan .
val max_float : float
The largest positive finite value of type float .
val min_float : float
The smallest positive, non-zero, non-denormalized value of type float .
val epsilon_float : float
The difference between 1.0 and the smallest exactly representable
floating-point number greater than 1.0 .
type fpclass =
| FP_normal (* Normal number, none of the below
*)
| FP_subnormal (* Number very close to 0.0, has reduced precision
*)
| FP_zero (* Number is 0.0 or -0.0
*)
| FP_infinite (* Number is positive or negative infinity
*)
| FP_nan (* Not a number: result of an undefined operation
*)
The five classes of floating-point numbers, as determined by the clas-
sify_float function.
val classify_float : float -> fpclass
Return the class of the given floating-point number: normal, subnormal,
zero, infinite, or not a number.
String operations
More string operations are provided in module String .
val (^) : string -> string -> string
String concatenation. Right-associative operator, see Ocaml_operators
for more information.
Raises Invalid_argument if the result is longer then than
Sys.max_string_length bytes.
Character operations
More character operations are provided in module Char .
val int_of_char : char -> int
Return the ASCII code of the argument.
val char_of_int : int -> char
Return the character with the given ASCII code.
Raises Invalid_argument if the argument is outside the range 0--255.
Unit operations
val ignore : 'a -> unit
Discard the value of its argument and return () . For instance, ig-
nore(f x) discards the result of the side-effecting function f . It is
equivalent to f x; () , except that the latter may generate a compiler
warning; writing ignore(f x) instead avoids the warning.
String conversion functions
val string_of_bool : bool -> string
Return the string representation of a boolean. As the returned values
may be shared, the user should not modify them directly.
val bool_of_string_opt : string -> bool option
Convert the given string to a boolean.
Return None if the string is not "true" or "false" .
Since 4.05
val bool_of_string : string -> bool
Same as bool_of_string_opt , but raise Invalid_argument
"bool_of_string" instead of returning None .
val string_of_int : int -> string
Return the string representation of an integer, in decimal.
val int_of_string_opt : string -> int option
Convert the given string to an integer. The string is read in decimal
(by default, or if the string begins with 0u ), in hexadecimal (if it
begins with 0x or 0X ), in octal (if it begins with 0o or 0O ), or in
binary (if it begins with 0b or 0B ).
The 0u prefix reads the input as an unsigned integer in the range [0,
2*max_int+1] . If the input exceeds max_int it is converted to the
signed integer min_int + input - max_int - 1 .
The _ (underscore) character can appear anywhere in the string and is
ignored.
Return None if the given string is not a valid representation of an in-
teger, or if the integer represented exceeds the range of integers rep-
resentable in type int .
Since 4.05
val int_of_string : string -> int
Same as int_of_string_opt , but raise Failure "int_of_string" instead
of returning None .
val string_of_float : float -> string
Return the string representation of a floating-point number.
val float_of_string_opt : string -> float option
Convert the given string to a float. The string is read in decimal (by
default) or in hexadecimal (marked by 0x or 0X ).
The format of decimal floating-point numbers is [-] dd.ddd (e|E) [+|-]
dd , where d stands for a decimal digit.
The format of hexadecimal floating-point numbers is [-] 0(x|X) hh.hhh
(p|P) [+|-] dd , where h stands for an hexadecimal digit and d for a
decimal digit.
In both cases, at least one of the integer and fractional parts must be
given; the exponent part is optional.
The _ (underscore) character can appear anywhere in the string and is
ignored.
Depending on the execution platforms, other representations of float-
ing-point numbers can be accepted, but should not be relied upon.
Return None if the given string is not a valid representation of a
float.
Since 4.05
val float_of_string : string -> float
Same as float_of_string_opt , but raise Failure "float_of_string" in-
stead of returning None .
Pair operations
val fst : 'a * 'b -> 'a
Return the first component of a pair.
val snd : 'a * 'b -> 'b
Return the second component of a pair.
List operations
More list operations are provided in module List .
val (@) : 'a list -> 'a list -> 'a list
List concatenation. Not tail-recursive (length of the first argument).
Right-associative operator, see Ocaml_operators for more information.
Input/output
Note: all input/output functions can raise Sys_error when the system
calls they invoke fail.
type in_channel
The type of input channel.
type out_channel
The type of output channel.
val stdin : in_channel
The standard input for the process.
val stdout : out_channel
The standard output for the process.
val stderr : out_channel
The standard error output for the process.
Output functions on standard output
val print_char : char -> unit
Print a character on standard output.
val print_string : string -> unit
Print a string on standard output.
val print_bytes : bytes -> unit
Print a byte sequence on standard output.
Since 4.02.0
val print_int : int -> unit
Print an integer, in decimal, on standard output.
val print_float : float -> unit
Print a floating-point number, in decimal, on standard output.
val print_endline : string -> unit
Print a string, followed by a newline character, on standard output and
flush standard output.
val print_newline : unit -> unit
Print a newline character on standard output, and flush standard out-
put. This can be used to simulate line buffering of standard output.
Output functions on standard error
val prerr_char : char -> unit
Print a character on standard error.
val prerr_string : string -> unit
Print a string on standard error.
val prerr_bytes : bytes -> unit
Print a byte sequence on standard error.
Since 4.02.0
val prerr_int : int -> unit
Print an integer, in decimal, on standard error.
val prerr_float : float -> unit
Print a floating-point number, in decimal, on standard error.
val prerr_endline : string -> unit
Print a string, followed by a newline character on standard error and
flush standard error.
val prerr_newline : unit -> unit
Print a newline character on standard error, and flush standard error.
Input functions on standard input
val read_line : unit -> string
Flush standard output, then read characters from standard input until a
newline character is encountered. Return the string of all characters
read, without the newline character at the end.
val read_int_opt : unit -> int option
Flush standard output, then read one line from standard input and con-
vert it to an integer.
Return None if the line read is not a valid representation of an inte-
ger.
Since 4.05
val read_int : unit -> int
Same as read_int_opt , but raise Failure "int_of_string" instead of re-
turning None .
val read_float_opt : unit -> float option
Flush standard output, then read one line from standard input and con-
vert it to a floating-point number.
Return None if the line read is not a valid representation of a float-
ing-point number.
Since 4.05.0
val read_float : unit -> float
Same as read_float_opt , but raise Failure "float_of_string" instead of
returning None .
General output functions
type open_flag =
| Open_rdonly (* open for reading.
*)
| Open_wronly (* open for writing.
*)
| Open_append (* open for appending: always write at end of file.
*)
| Open_creat (* create the file if it does not exist.
*)
| Open_trunc (* empty the file if it already exists.
*)
| Open_excl (* fail if Open_creat and the file already exists.
*)
| Open_binary (* open in binary mode (no conversion).
*)
| Open_text (* open in text mode (may perform conversions).
*)
| Open_nonblock (* open in non-blocking mode.
*)
Opening modes for open_out_gen and open_in_gen .
val open_out : string -> out_channel
Open the named file for writing, and return a new output channel on
that file, positioned at the beginning of the file. The file is trun-
cated to zero length if it already exists. It is created if it does not
already exists.
val open_out_bin : string -> out_channel
Same as open_out , but the file is opened in binary mode, so that no
translation takes place during writes. On operating systems that do not
distinguish between text mode and binary mode, this function behaves
like open_out .
val open_out_gen : open_flag list -> int -> string -> out_channel
open_out_gen mode perm filename opens the named file for writing, as
described above. The extra argument mode specifies the opening mode.
The extra argument perm specifies the file permissions, in case the
file must be created. open_out and open_out_bin are special cases of
this function.
val flush : out_channel -> unit
Flush the buffer associated with the given output channel, performing
all pending writes on that channel. Interactive programs must be care-
ful about flushing standard output and standard error at the right
time.
val flush_all : unit -> unit
Flush all open output channels; ignore errors.
val output_char : out_channel -> char -> unit
Write the character on the given output channel.
val output_string : out_channel -> string -> unit
Write the string on the given output channel.
val output_bytes : out_channel -> bytes -> unit
Write the byte sequence on the given output channel.
Since 4.02.0
val output : out_channel -> bytes -> int -> int -> unit
output oc buf pos len writes len characters from byte sequence buf ,
starting at offset pos , to the given output channel oc .
Raises Invalid_argument if pos and len do not designate a valid range
of buf .
val output_substring : out_channel -> string -> int -> int -> unit
Same as output but take a string as argument instead of a byte se-
quence.
Since 4.02.0
val output_byte : out_channel -> int -> unit
Write one 8-bit integer (as the single character with that code) on the
given output channel. The given integer is taken modulo 256.
val output_binary_int : out_channel -> int -> unit
Write one integer in binary format (4 bytes, big-endian) on the given
output channel. The given integer is taken modulo 2^32. The only re-
liable way to read it back is through the input_binary_int function.
The format is compatible across all machines for a given version of
OCaml.
val output_value : out_channel -> 'a -> unit
Write the representation of a structured value of any type to a chan-
nel. Circularities and sharing inside the value are detected and pre-
served. The object can be read back, by the function input_value . See
the description of module Marshal for more information. output_value
is equivalent to Marshal.to_channel with an empty list of flags.
val seek_out : out_channel -> int -> unit
seek_out chan pos sets the current writing position to pos for channel
chan . This works only for regular files. On files of other kinds (such
as terminals, pipes and sockets), the behavior is unspecified.
val pos_out : out_channel -> int
Return the current writing position for the given channel. Does not
work on channels opened with the Open_append flag (returns unspecified
results). For files opened in text mode under Windows, the returned
position is approximate (owing to end-of-line conversion); in particu-
lar, saving the current position with pos_out , then going back to this
position using seek_out will not work. For this programming idiom to
work reliably and portably, the file must be opened in binary mode.
val out_channel_length : out_channel -> int
Return the size (number of characters) of the regular file on which the
given channel is opened. If the channel is opened on a file that is
not a regular file, the result is meaningless.
val close_out : out_channel -> unit
Close the given channel, flushing all buffered write operations. Out-
put functions raise a Sys_error exception when they are applied to a
closed output channel, except close_out and flush , which do nothing
when applied to an already closed channel. Note that close_out may
raise Sys_error if the operating system signals an error when flushing
or closing.
val close_out_noerr : out_channel -> unit
Same as close_out , but ignore all errors.
val set_binary_mode_out : out_channel -> bool -> unit
set_binary_mode_out oc true sets the channel oc to binary mode: no
translations take place during output. set_binary_mode_out oc false
sets the channel oc to text mode: depending on the operating system,
some translations may take place during output. For instance, under
Windows, end-of-lines will be translated from \n to \r\n . This func-
tion has no effect under operating systems that do not distinguish be-
tween text mode and binary mode.
General input functions
val open_in : string -> in_channel
Open the named file for reading, and return a new input channel on that
file, positioned at the beginning of the file.
val open_in_bin : string -> in_channel
Same as open_in , but the file is opened in binary mode, so that no
translation takes place during reads. On operating systems that do not
distinguish between text mode and binary mode, this function behaves
like open_in .
val open_in_gen : open_flag list -> int -> string -> in_channel
open_in_gen mode perm filename opens the named file for reading, as de-
scribed above. The extra arguments mode and perm specify the opening
mode and file permissions. open_in and open_in_bin are special cases
of this function.
val input_char : in_channel -> char
Read one character from the given input channel.
Raises End_of_file if there are no more characters to read.
val input_line : in_channel -> string
Read characters from the given input channel, until a newline character
is encountered. Return the string of all characters read, without the
newline character at the end.
Raises End_of_file if the end of the file is reached at the beginning
of line.
val input : in_channel -> bytes -> int -> int -> int
input ic buf pos len reads up to len characters from the given channel
ic , storing them in byte sequence buf , starting at character number
pos . It returns the actual number of characters read, between 0 and
len (inclusive). A return value of 0 means that the end of file was
reached. A return value between 0 and len exclusive means that not all
requested len characters were read, either because no more characters
were available at that time, or because the implementation found it
convenient to do a partial read; input must be called again to read the
remaining characters, if desired. (See also really_input for reading
exactly len characters.) Exception Invalid_argument "input" is raised
if pos and len do not designate a valid range of buf .
val really_input : in_channel -> bytes -> int -> int -> unit
really_input ic buf pos len reads len characters from channel ic ,
storing them in byte sequence buf , starting at character number pos .
Raises End_of_file if the end of file is reached before len characters
have been read.
Raises Invalid_argument if pos and len do not designate a valid range
of buf .
val really_input_string : in_channel -> int -> string
really_input_string ic len reads len characters from channel ic and re-
turns them in a new string.
Since 4.02.0
Raises End_of_file if the end of file is reached before len characters
have been read.
val input_byte : in_channel -> int
Same as input_char , but return the 8-bit integer representing the
character.
Raises End_of_file if an end of file was reached.
val input_binary_int : in_channel -> int
Read an integer encoded in binary format (4 bytes, big-endian) from the
given input channel. See output_binary_int .
Raises End_of_file if an end of file was reached while reading the in-
teger.
val input_value : in_channel -> 'a
Read the representation of a structured value, as produced by out-
put_value , and return the corresponding value. This function is iden-
tical to Marshal.from_channel ; see the description of module Marshal
for more information, in particular concerning the lack of type safety.
val seek_in : in_channel -> int -> unit
seek_in chan pos sets the current reading position to pos for channel
chan . This works only for regular files. On files of other kinds, the
behavior is unspecified.
val pos_in : in_channel -> int
Return the current reading position for the given channel. For files
opened in text mode under Windows, the returned position is approximate
(owing to end-of-line conversion); in particular, saving the current
position with pos_in , then going back to this position using seek_in
will not work. For this programming idiom to work reliably and
portably, the file must be opened in binary mode.
val in_channel_length : in_channel -> int
Return the size (number of characters) of the regular file on which the
given channel is opened. If the channel is opened on a file that is
not a regular file, the result is meaningless. The returned size does
not take into account the end-of-line translations that can be per-
formed when reading from a channel opened in text mode.
val close_in : in_channel -> unit
Close the given channel. Input functions raise a Sys_error exception
when they are applied to a closed input channel, except close_in ,
which does nothing when applied to an already closed channel.
val close_in_noerr : in_channel -> unit
Same as close_in , but ignore all errors.
val set_binary_mode_in : in_channel -> bool -> unit
set_binary_mode_in ic true sets the channel ic to binary mode: no
translations take place during input. set_binary_mode_out ic false
sets the channel ic to text mode: depending on the operating system,
some translations may take place during input. For instance, under
Windows, end-of-lines will be translated from \r\n to \n . This func-
tion has no effect under operating systems that do not distinguish be-
tween text mode and binary mode.
Operations on large files
module LargeFile : sig end
Operations on large files. This sub-module provides 64-bit variants of
the channel functions that manipulate file positions and file sizes.
By representing positions and sizes by 64-bit integers (type int64 )
instead of regular integers (type int ), these alternate functions al-
low operating on files whose sizes are greater than max_int .
References
type 'a ref = {
mutable contents : 'a ;
}
The type of references (mutable indirection cells) containing a value
of type 'a .
val ref : 'a -> 'a ref
Return a fresh reference containing the given value.
val (!) : 'a ref -> 'a
!r returns the current contents of reference r . Equivalent to fun r
-> r.contents . Unary operator, see Ocaml_operators for more informa-
tion.
val (:=) : 'a ref -> 'a -> unit
r := a stores the value of a in reference r . Equivalent to fun r v ->
r.contents <- v . Right-associative operator, see Ocaml_operators for
more information.
val incr : int ref -> unit
Increment the integer contained in the given reference. Equivalent to
fun r -> r := succ !r .
val decr : int ref -> unit
Decrement the integer contained in the given reference. Equivalent to
fun r -> r := pred !r .
Result type
type ('a, 'b) result =
| Ok of 'a
| Error of 'b
Since 4.03.0
Operations on format strings
Format strings are character strings with special lexical conventions
that defines the functionality of formatted input/output functions.
Format strings are used to read data with formatted input functions
from module Scanf and to print data with formatted output functions
from modules Printf and Format .
Format strings are made of three kinds of entities:
-conversions specifications, introduced by the special character '%'
followed by one or more characters specifying what kind of argument to
read or print,
-formatting indications, introduced by the special character '@' fol-
lowed by one or more characters specifying how to read or print the ar-
gument,
-plain characters that are regular characters with usual lexical con-
ventions. Plain characters specify string literals to be read in the
input or printed in the output.
There is an additional lexical rule to escape the special characters
'%' and '@' in format strings: if a special character follows a '%'
character, it is treated as a plain character. In other words, "%%" is
considered as a plain '%' and "%@" as a plain '@' .
For more information about conversion specifications and formatting in-
dications available, read the documentation of modules Scanf , Printf
and Format .
Format strings have a general and highly polymorphic type ('a, 'b, 'c,
'd, 'e, 'f) format6 . The two simplified types, format and format4 be-
low are included for backward compatibility with earlier releases of
OCaml.
The meaning of format string type parameters is as follows:
- 'a is the type of the parameters of the format for formatted output
functions ( printf -style functions); 'a is the type of the values read
by the format for formatted input functions ( scanf -style functions).
- 'b is the type of input source for formatted input functions and the
type of output target for formatted output functions. For printf
-style functions from module Printf , 'b is typically out_channel ; for
printf -style functions from module Format , 'b is typically For-
mat.formatter ; for scanf -style functions from module Scanf , 'b is
typically Scanf.Scanning.in_channel .
Type argument 'b is also the type of the first argument given to user's
defined printing functions for %a and %t conversions, and user's de-
fined reading functions for %r conversion.
- 'c is the type of the result of the %a and %t printing functions, and
also the type of the argument transmitted to the first argument of
kprintf -style functions or to the kscanf -style functions.
- 'd is the type of parameters for the scanf -style functions.
- 'e is the type of the receiver function for the scanf -style func-
tions.
- 'f is the final result type of a formatted input/output function in-
vocation: for the printf -style functions, it is typically unit ; for
the scanf -style functions, it is typically the result type of the re-
ceiver function.
type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam-
linternalFormatBasics.format6
type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
Converts a format string into a string.
val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
'd, 'e, 'f) format6
format_of_string s returns a format string read from the string literal
s . Note: format_of_string can not convert a string argument that is
not a literal. If you need this functionality, use the more general
Scanf.format_from_string function.
val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
string that behaves as the concatenation of format strings f1 and f2 :
in case of formatted output, it accepts arguments from f1 , then argu-
ments from f2 ; in case of formatted input, it returns results from f1
, then results from f2 . Right-associative operator, see Ocaml_opera-
tors for more information.
Program termination
val exit : int -> 'a
Terminate the process, returning the given status code to the operating
system: usually 0 to indicate no errors, and a small positive integer
to indicate failure. All open output channels are flushed with
flush_all . An implicit exit 0 is performed each time a program termi-
nates normally. An implicit exit 2 is performed if the program termi-
nates early because of an uncaught exception.
val at_exit : (unit -> unit) -> unit
Register the given function to be called at program termination time.
The functions registered with at_exit will be called when the program
does any of the following:
-executes exit
-terminates, either normally or because of an uncaught exception
-executes the C function caml_shutdown . The functions are called in
'last in, first out' order: the function most recently added with
at_exit is called first.
Standard library modules
module Arg : (module Stdlib__Arg)
module Array : (module Stdlib__Array)
module ArrayLabels : (module Stdlib__ArrayLabels)
module Atomic : (module Stdlib__Atomic)
module Bigarray : (module Stdlib__Bigarray)
module Bool : (module Stdlib__Bool)
module Buffer : (module Stdlib__Buffer)
module Bytes : (module Stdlib__Bytes)
module BytesLabels : (module Stdlib__BytesLabels)
module Callback : (module Stdlib__Callback)
module Char : (module Stdlib__Char)
module Complex : (module Stdlib__Complex)
module Digest : (module Stdlib__Digest)
module Either : (module Stdlib__Either)
module Ephemeron : (module Stdlib__Ephemeron)
module Filename : (module Stdlib__Filename)
module Float : (module Stdlib__Float)
module Format : (module Stdlib__Format)
module Fun : (module Stdlib__Fun)
module Gc : (module Stdlib__Gc)
module Genlex : (module Stdlib__Genlex)
module Hashtbl : (module Stdlib__Hashtbl)
module Int : (module Stdlib__Int)
module Int32 : (module Stdlib__Int32)
module Int64 : (module Stdlib__Int64)
module Lazy : (module Stdlib__Lazy)
module Lexing : (module Stdlib__Lexing)
module List : (module Stdlib__List)
module ListLabels : (module Stdlib__ListLabels)
module Map : (module Stdlib__Map)
module Marshal : (module Stdlib__Marshal)
module MoreLabels : (module Stdlib__MoreLabels)
module Nativeint : (module Stdlib__Nativeint)
module Obj : (module Stdlib__Obj)
module Oo : (module Stdlib__Oo)
module Option : (module Stdlib__Option)
module Parsing : (module Stdlib__Parsing)
module Pervasives : (module Stdlib__Pervasives)
module Printexc : (module Stdlib__Printexc)
module Printf : (module Stdlib__Printf)
module Queue : (module Stdlib__Queue)
module Random : (module Stdlib__Random)
module Result : (module Stdlib__Result)
module Scanf : (module Stdlib__Scanf)
module Seq : (module Stdlib__Seq)
module Set : (module Stdlib__Set)
module Stack : (module Stdlib__Stack)
module StdLabels : (module Stdlib__StdLabels)
module Stream : (module Stdlib__Stream)
module String : (module Stdlib__String)
module StringLabels : (module Stdlib__StringLabels)
module Sys : (module Stdlib__Sys)
module Uchar : (module Stdlib__Uchar)
module Unit : (module Stdlib__Unit)
module Weak : (module Stdlib__Weak)
OCamldoc 2023-02-12 Stdlib(3o)
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