Pervasives(3) OCaml library Pervasives(3)NAMEPervasives - The initially opened module.
Module
Module PervasivesDocumentation
Module Pervasives
: sig end
The initially opened module.
This module provides the basic operations over the built-in types (num‐
bers, booleans, strings, exceptions, references, lists, arrays,
input-output channels, ...).
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 Pervasives .
=== Exceptions ===
val raise : exn -> 'a
Raise the given exception value
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.
=== 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.
val (<>) : 'a -> 'a -> bool
Negation of Pervasives.(=) .
val (<) : 'a -> 'a -> bool
See Pervasives.(>=) .
val (>) : 'a -> 'a -> bool
See Pervasives.(>=) .
val (<=) : 'a -> 'a -> bool
See Pervasives.(>=) .
val (>=) : 'a -> 'a -> bool
Structural ordering functions. These functions coincide with the usual
orderings over integers, characters, strings and floating-point num‐
bers, and extend them to a total ordering over all types. The ordering
is compatible with ( = ) . As in the case of ( = ) , mutable structures
are compared by contents. Comparison between functional values raises
Invalid_argument . Comparison between cyclic structures may not termi‐
nate.
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
ordering implemented by compare is compatible with the comparison pred‐
icates = , < and > defined above, with one difference on the treatment
of the float value Pervasives.nan . Namely, the comparison predicates
treat nan as different from any other float value, including itself;
while compare treats nan as equal to itself and less than any other
float value. This treatment of nan ensures that compare defines a
total ordering relation.
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
Array.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, strings, 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 .
val (!=) : 'a -> 'a -> bool
Negation of Pervasives.(==) .
=== 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.
val (&) : bool -> bool -> bool
Deprecated.
Pervasives.(&&) should be used instead.
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.
val (or) : bool -> bool -> bool
Deprecated.
Pervasives.(||) should be used instead.
=== Composition operators ===
val (|>) : 'a -> ('a -> 'b) -> 'b
Reverse-application operator: x |> f |> g is exactly equivalent to g (f
(x)) .
Since 4.01
val (@@) : ('a -> 'b) -> 'a -> 'b
Application operator: g @@ f @@ x is exactly equivalent to g (f (x)) .
Since 4.01
=== Integer arithmetic ===
=== Integers are 31 bits wide (or 63 bits on 64-bit processors). All
operations are taken modulo 2^{31} (or 2^{63}). They do not fail on
overflow. ===
val (~-) : int -> int
Unary negation. You can also write - e instead of ~- e .
val (~+) : int -> int
Unary addition. You can also write + e instead of ~+ e .
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.
val (-) : int -> int -> int
Integer subtraction.
val ( * ) : int -> int -> int
Integer multiplication.
val (/) : int -> int -> int
Integer division. Raise Division_by_zero if the second argument is 0.
Integer division rounds the real quotient of its arguments 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) .
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 . Raise 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.
val (lor) : int -> int -> int
Bitwise logical or.
val (lxor) : int -> int -> int
Bitwise logical exclusive or.
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 >= bitsize , where bitsize is 32 on a 32-bit platform and 64
on a 64-bit platform.
val (lsr) : int -> int -> int
n lsr m shifts n to the right by m bits. This is a logical shift:
zeroes are inserted regardless of the sign of n . The result is
unspecified if m < 0 or m >= bitsize .
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 >= bitsize .
=== Floating-point arithmetic OCaml's floating-point numbers follow the
IEEE 754 standard, using double precision (64 bits) numbers. Float‐
ing-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 floating-point computations as expected: for
instance, 1.0 /. infinity is 0.0, and any arithmetic operation with nan
as argument returns nan as result. ===
val (~-.) : float -> float
Unary negation. You can also write -. e instead of ~-. e .
val (~+.) : float -> float
Unary addition. You can also write +. e instead of ~+. e .
Since 3.12.0
val (+.) : float -> float -> float
Floating-point addition
val (-.) : float -> float -> float
Floating-point subtraction
val ( *. ) : float -> float -> float
Floating-point multiplication
val (/.) : float -> float -> float
Floating-point division.
val ( ** ) : float -> float -> float
Exponentiation.
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] .
Result 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] .
Result 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.
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 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
returned 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 Pervasives.float_of_int .
val float_of_int : int -> float
Convert an integer to floating-point.
val truncate : float -> int
Same as Pervasives.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
operation 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 Perva‐
sives.classify_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.
=== Character operations More character operations are provided in mod‐
ule 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. Raise Invalid_argument
char_of_int 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,
ignore(f x) discards the result of the side-effecting function f . It
is equivalent to f x; () , except that the latter may generate a com‐
piler 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 : string -> bool
Convert the given string to a boolean. Raise Invalid_argument
bool_of_string if the string is not true or false .
val string_of_int : int -> string
Return the string representation of an integer, in decimal.
val int_of_string : string -> int
Convert the given string to an integer. The string is read in decimal
(by default) or in hexadecimal (if it begins with 0x or 0X ), octal (if
it begins with 0o or 0O ), or binary (if it begins with 0b or 0B ).
Raise Failure int_of_string if the given string is not a valid repre‐
sentation of an integer, or if the integer represented exceeds the
range of integers representable in type int .
val string_of_float : float -> string
Return the string representation of a floating-point number.
val float_of_string : string -> float
Convert the given string to a float. Raise Failure float_of_string if
the given string is not a valid representation of a float.
=== 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.
=== 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_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_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 : unit -> int
Flush standard output, then read one line from standard input and con‐
vert it to an integer. Raise Failure int_of_string if the line read is
not a valid representation of an integer.
val read_float : unit -> float
Flush standard output, then read one line from standard input and con‐
vert it to a floating-point number. The result is unspecified if the
line read is not a valid representation of a floating-point number.
=== 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 Pervasives.open_out_gen and Pervasives.open_in_gen .
val open_out : string -> out_channel
Open the named file for writing, and return a new output channel on
that file, positionned 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 Pervasives.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 func‐
tion behaves like Pervasives.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 specify the opening mode. The
extra argument perm specifies the file permissions, in case the file
must be created. Pervasives.open_out and Pervasives.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 : out_channel -> string -> int -> int -> unit
output oc buf pos len writes len characters from string buf , starting
at offset pos , to the given output channel oc . Raise Invalid_argu‐
ment output if pos and len do not designate a valid substring of buf .
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
reliable way to read it back is through the Pervasives.input_binary_int
function. The format is compatible across all machines for a given ver‐
sion 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 Perva‐
sives.input_value . See the description of module Marshal for more
information. Pervasives.output_value is equivalent to Marshal.to_chan‐
nel 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).
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
between 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, positionned at the beginning of the file.
val open_in_bin : string -> in_channel
Same as Pervasives.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 Pervasives.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
described above. The extra arguments mode and perm specify the opening
mode and file permissions. Pervasives.open_in and Perva‐
sives.open_in_bin are special cases of this function.
val input_char : in_channel -> char
Read one character from the given input channel. Raise 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. Raise End_of_file if the end of the file
is reached at the beginning of line.
val input : in_channel -> string -> int -> int -> int
input ic buf pos len reads up to len characters from the given channel
ic , storing them in string 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 Pervasives.really_input
for reading exactly len characters.) Exception Invalid_argument input
is raised if pos and len do not designate a valid substring of buf .
val really_input : in_channel -> string -> int -> int -> unit
really_input ic buf pos len reads len characters from channel ic ,
storing them in string buf , starting at character number pos . Raise
End_of_file if the end of file is reached before len characters have
been read. Raise Invalid_argument really_input if pos and len do not
designate a valid substring of buf .
val input_byte : in_channel -> int
Same as Pervasives.input_char , but return the 8-bit integer represent‐
ing the character. Raise 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 Pervasives.output_binary_int . Raise
End_of_file if an end of file was reached while reading the integer.
val input_value : in_channel -> 'a
Read the representation of a structured value, as produced by Perva‐
sives.output_value , and return the corresponding value. This function
is identical 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.
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
between 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
allow 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 .
val (:=) : 'a ref -> 'a -> unit
r := a stores the value of a in reference r . Equivalent to fun r v ->
r.contents <- v .
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 .
=== Operations on format strings ===
=== Format strings are character strings with special lexical conven‐
tions that defines the functionality of formatted input/output func‐
tions. Format strings are used to read data with formatted input func‐
tions from module Scanf and to print data with formatted output func‐
tions from modules Printf and Format. Format strings are made of three
kinds of entities: - conversions specifications, introduced by the spe‐
cial character '%' followed by one or more characters specifying what
kind of argument to read or print, - formatting indications, introduced
by the special character '@' followed by one or more characters speci‐
fying how to read or print the argument, - plain characters that are
regular characters with usual lexical conventions. Plain characters
specify string literals to be read in the input or printed in the out‐
put. There is an additional lexical rule to escape the special charac‐
ters '%' 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 informa‐
tion about conversion specifications and formatting indications avail‐
able, read the documentation of modules Scanf, Printf and Format. ===
type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
Format strings have a general and highly polymorphic type ('a, 'b, 'c,
'd, 'e, 'f) format6 . Type format6 is built in. The two simplified
types, format and format4 below 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
defined 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
invocation: for the printf -style functions, it is typically unit ; for
the scanf -style functions, it is typically the result type of the
receiver function.
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 .
=== 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
executes Pervasives.exit , or terminates, either normally or because of
an uncaught exception. The functions are called in 'last in, first
out' order: the function most recently added with at_exit is called
first.
OCamldoc 2013-10-24 Pervasives(3)
