module Pervasives: sig .. end
The initially opened module.
This module provides the basic operations over the built-in types
(numbers, booleans, strings, exceptions, references, lists, arrays,
input-output channels, ...).
This module is automatically opened at the beginning of each compilation.
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
provided for use in your programs.
Comparisons
val (=) : 'a -> 'a -> bool
e1 = e2
tests for structural equality of e1
and e2
.
Mutable structures (e.g. references and arrays) are equal
if and only if their current 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
val (<) : 'a -> 'a -> bool
val (>) : 'a -> 'a -> bool
val (<=) : 'a -> 'a -> bool
val (>=) : 'a -> 'a -> bool
Structural ordering functions. These functions coincide with
the usual orderings over integers, characters, strings
and floating-point numbers, 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 terminate.
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 predicates
=
,
<
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
.
compare
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
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
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
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
negative if the argument is min_int
.
val max_int : int
The greatest representable integer.
val min_int : int
The smallest representable integer.
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.
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
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 numerically-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_of_int : int -> float
Convert an integer to floating-point.
val truncate : float -> int
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 representable 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 floating-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 |
| |
FP_subnormal |
| |
FP_zero |
| |
FP_infinite |
| |
FP_nan |
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 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.
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
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 : 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 representation 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.
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 output. 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 convert 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 convert it to a floating-point number.
The result is unspecified if the line read is not a valid
representation of a floating-point number.
type open_flag =
| |
Open_rdonly |
| |
Open_wronly |
| |
Open_append |
| |
Open_creat |
| |
Open_trunc |
| |
Open_excl |
| |
Open_binary |
| |
Open_text |
| |
Open_nonblock |
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 truncated 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 function 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 careful 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_argument "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 version of OCaml.
val output_value : out_channel -> 'a -> unit
Write the representation of a structured value of any type
to a channel. Circularities and sharing inside the value
are detected and preserved. The object can be read back,
by the function
Pervasives.input_value
. See the description of module
Marshal
for more information.
Pervasives.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).
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.
Output 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 function has no effect under operating systems that
do not distinguish between text mode and binary mode.
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
Pervasives.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 representing
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
Pervasives.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 performed 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 function 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.
References
type 'a ref = {
}
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
.
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
'@'
followed by one or more characters specifying 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 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
indications available, 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
Format.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 functions.
'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
arguments 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
terminates normally. An implicit exit 2
is performed if the program
terminates 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.