Module Stdlib
: sigend
The OCaml Standard library.
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 Stdlib .
In 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 .
Exceptionsvalraise : exn->'a
Raise the given exception value
valraise_notrace : exn->'a
A faster version raise which does not record the backtrace.
Since 4.02
valinvalid_arg : string->'a
Raise exception Invalid_argument with the given string.
valfailwith : string->'a
Raise exception Failure with the given string.
exceptionExit
The Exit exception is not raised by any library function. It is provided for use in your programs.
exceptionMatch_failureof(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).
exceptionAssert_failureof(string*int*int)
Exception raised when an assertion fails. The arguments are the location of the assert keyword in the
source code (file name, line number, column number).
exceptionInvalid_argumentofstring
Exception raised by library functions to signal that the given arguments do not make sense. The string
gives some information to the programmer. As a general rule, this exception should not be caught, it
denotes a programming error and the code should be modified not to trigger it.
exceptionFailureofstring
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 because it may change in future versions (use Failure _ instead).
exceptionNot_found
Exception raised by search functions when the desired object could not be found.
exceptionOut_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.)
exceptionStack_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.
exceptionSys_errorofstring
Exception raised by the input/output functions to report an operating system error. The string is meant
to give some information to the programmer; you must not pattern match on the string literal because it
may change in future versions (use Sys_error _ instead).
exceptionEnd_of_file
Exception raised by input functions to signal that the end of file has been reached.
exceptionDivision_by_zero
Exception raised by integer division and remainder operations when their second argument is zero.
exceptionSys_blocked_io
A special case of Sys_error raised when no I/O is possible on a non-blocking I/O channel.
exceptionUndefined_recursive_moduleof(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).
Comparisonsval(=) : 'a->'a->boole1=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. 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 information.
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 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. Left-associative operator, see Ocaml_operators for more
information.
valcompare : 'a->'a->intcomparexy 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 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.
valmin : 'a->'a->'a
Return the smaller of the two arguments. The result is unspecified if one of the arguments contains the
float value nan .
valmax : '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->boole1==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 comparee1e2=0 .
Left-associative operator, see Ocaml_operators for more information.
val(!=) : 'a->'a->bool
Negation of (==) . Left-associative operator, see Ocaml_operators for more information.
Booleanoperationsvalnot : 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
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
information.
Debuggingval__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
val__FILE__ : string__FILE__ returns the name of the file currently being parsed by the compiler.
Since 4.02
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
val__MODULE__ : string__MODULE__ returns the module name of the file being parsed by the compiler.
Since 4.02
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 character position in the line.
Since 4.02
val__FUNCTION__ : string__FUNCTION__ returns the name of the current function or method, including any enclosing modules or
classes.
Since 4.12
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 standard error format of OCaml: "File %S, line %d, characters %d-%d".
Since 4.02
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
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 expression expr 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 character position in the line.
Since 4.02
Compositionoperatorsval(|>) : '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 information.
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
Integerarithmetic
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 operator, see Ocaml_operators for more
information.
val(~+) : int->int
Unary addition. You can also write +e instead of ~+e . Unary operator, see Ocaml_operators for more
information.
Since 3.12
valsucc : int->intsuccx is x+1 .
valpred : int->intpredx 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 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) . Left-associative operator, see Ocaml_operators
for more information.
RaisesDivision_by_zero if the second argument is 0.
val(mod) : int->int->int
Integer remainder. If y is not zero, the result of xmody satisfies the following properties: x=(x/y)*y+xmody and abs(xmody)<=abs(y)-1 . If y=0 , xmody raises Division_by_zero . Note
that xmody is negative only if x<0 . Left-associative operator, see Ocaml_operators for more
information.
RaisesDivision_by_zero if y is zero.
valabs : int->intabsx is the absolute value of x . On min_int this is min_int itself and thus remains negative.
valmax_int : int
The greatest representable integer.
valmin_int : int
The smallest representable integer.
Bitwiseoperationsval(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_operators for more information.
vallnot : int->int
Bitwise logical negation.
val(lsl) : int->int->intnlslm 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_operators for more information.
val(lsr) : int->int->intnlsrm 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>Sys.int_size . Right-associative operator, see
Ocaml_operators for more information.
val(asr) : int->int->intnasrm 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-pointarithmetic
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 , basic arithmetic
operations ( +. , -. , *. , /. ) with nan as an argument return nan , ...
val(~-.) : float->float
Unary negation. You can also write -.e instead of ~-.e . Unary operator, see Ocaml_operators for more
information.
val(~+.) : float->float
Unary addition. You can also write +.e instead of ~+.e . Unary operator, see Ocaml_operators for more
information.
Since 3.12
val(+.) : float->float->float
Floating-point addition. Left-associative operator, see Ocaml_operators for more information.
val(-.) : float->float->float
Floating-point subtraction. Left-associative operator, see Ocaml_operators 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_operators for more information.
val(**) : float->float->float
Exponentiation. Right-associative operator, see Ocaml_operators for more information.
valsqrt : float->float
Square root.
valexp : float->float
Exponential.
vallog : float->float
Natural logarithm.
vallog10 : float->float
Base 10 logarithm.
valexpm1 : float->floatexpm1x computes expx-.1.0 , giving numerically-accurate results even if x is close to 0.0 .
Since 3.12
vallog1p : float->floatlog1px computes log(1.0+.x) (natural logarithm), giving numerically-accurate results even if x is
close to 0.0 .
Since 3.12
valcos : float->float
Cosine. Argument is in radians.
valsin : float->float
Sine. Argument is in radians.
valtan : float->float
Tangent. Argument is in radians.
valacos : 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 .
valasin : 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 .
valatan : float->float
Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
valatan2 : float->float->floatatan2yx 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 .
valhypot : float->float->floathypotxy 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
valcosh : float->float
Hyperbolic cosine. Argument is in radians.
valsinh : float->float
Hyperbolic sine. Argument is in radians.
valtanh : float->float
Hyperbolic tangent. Argument is in radians.
valacosh : 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
valasinh : float->float
Hyperbolic arc sine. The argument and result range over the entire real line. Result is in radians.
Since 4.13
valatanh : 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
valceil : float->float
Round above to an integer value. ceilf returns the least integer value greater than or equal to f .
The result is returned as a float.
valfloor : float->float
Round below to an integer value. floorf returns the greatest integer value less than or equal to f .
The result is returned as a float.
valabs_float : float->floatabs_floatf returns the absolute value of f .
valcopysign : float->float->floatcopysignxy 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
valmod_float : float->float->floatmod_floatab 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.
valfrexp : float->float*intfrexpf 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 .
valldexp : float->int->floatldexpxn returns x*.2**n .
valmodf : float->float*floatmodff returns the pair of the fractional and integral part of f .
valfloat : int->float
Same as float_of_int .
valfloat_of_int : int->float
Convert an integer to floating-point.
valtruncate : float->int
Same as int_of_float .
valint_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.
valinfinity : float
Positive infinity.
valneg_infinity : float
Negative infinity.
valnan : 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, unless
otherwise specified in IEEE 754 standard. As for floating-point comparisons, = , < , <= , > and >=
return false and <> returns true if one or both of their arguments is nan .
nan is a quiet NaN since 5.1; it was a signaling NaN before.
valmax_float : float
The largest positive finite value of type float .
valmin_float : float
The smallest positive, non-zero, non-denormalized value of type float .
valepsilon_float : float
The difference between 1.0 and the smallest exactly representable floating-point number greater than 1.0
.
typefpclass =
| 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 classify_float function.
valclassify_float : float->fpclass
Return the class of the given floating-point number: normal, subnormal, zero, infinite, or not a number.
Stringoperations
More string operations are provided in module String .
val(^) : string->string->string
String concatenation. Right-associative operator, see Ocaml_operators for more information.
RaisesInvalid_argument if the result is longer then than Sys.max_string_length bytes.
Characteroperations
More character operations are provided in module Char .
valint_of_char : char->int
Return the ASCII code of the argument.
valchar_of_int : int->char
Return the character with the given ASCII code.
RaisesInvalid_argument if the argument is outside the range 0--255.
Unitoperationsvalignore : 'a->unit
Discard the value of its argument and return () . For instance, ignore(fx) discards the result of the
side-effecting function f . It is equivalent to fx;() , except that the latter may generate a compiler
warning; writing ignore(fx) instead avoids the warning.
Stringconversionfunctionsvalstring_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.
valbool_of_string_opt : string->booloption
Convert the given string to a boolean.
Return None if the string is not "true" or "false" .
Since 4.05
valbool_of_string : string->bool
Same as bool_of_string_opt , but raise Invalid_argument"bool_of_string" instead of returning None .
valstring_of_int : int->string
Return the string representation of an integer, in decimal.
valint_of_string_opt : string->intoption
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 integer, or if the integer
represented exceeds the range of integers representable in type int .
Since 4.05
valint_of_string : string->int
Same as int_of_string_opt , but raise Failure"int_of_string" instead of returning None .
valstring_of_float : float->string
Return a string representation of a floating-point number.
This conversion can involve a loss of precision. For greater control over the manner in which the number
is printed, see Printf .
valfloat_of_string_opt : string->floatoption
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 floating-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
valfloat_of_string : string->float
Same as float_of_string_opt , but raise Failure"float_of_string" instead of returning None .
Pairoperationsvalfst : 'a*'b->'a
Return the first component of a pair.
valsnd : 'a*'b->'b
Return the second component of a pair.
Listoperations
More list operations are provided in module List .
val(@) : 'alist->'alist->'alistl0@l1 appends l1 to l0 . Same function as List.append . Right-associative operator, see
Ocaml_operators for more information.
Since 5.1 this function is tail-recursive.
Input/output
Note: all input/output functions can raise Sys_error when the system calls they invoke fail.
typein_channel
The type of input channel.
typeout_channel
The type of output channel.
valstdin : in_channel
The standard input for the process.
valstdout : out_channel
The standard output for the process.
valstderr : out_channel
The standard error output for the process.
Outputfunctionsonstandardoutputvalprint_char : char->unit
Print a character on standard output.
valprint_string : string->unit
Print a string on standard output.
valprint_bytes : bytes->unit
Print a byte sequence on standard output.
Since 4.02
valprint_int : int->unit
Print an integer, in decimal, on standard output.
valprint_float : float->unit
Print a floating-point number, in decimal, on standard output.
The conversion of the number to a string uses string_of_float and can involve a loss of precision.
valprint_endline : string->unit
Print a string, followed by a newline character, on standard output and flush standard output.
valprint_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.
Outputfunctionsonstandarderrorvalprerr_char : char->unit
Print a character on standard error.
valprerr_string : string->unit
Print a string on standard error.
valprerr_bytes : bytes->unit
Print a byte sequence on standard error.
Since 4.02
valprerr_int : int->unit
Print an integer, in decimal, on standard error.
valprerr_float : float->unit
Print a floating-point number, in decimal, on standard error.
The conversion of the number to a string uses string_of_float and can involve a loss of precision.
valprerr_endline : string->unit
Print a string, followed by a newline character on standard error and flush standard error.
valprerr_newline : unit->unit
Print a newline character on standard error, and flush standard error.
Inputfunctionsonstandardinputvalread_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.
RaisesEnd_of_file if the end of the file is reached at the beginning of line.
valread_int_opt : unit->intoption
Flush standard output, then read one line from standard input and convert it to an integer.
Return None if the line read is not a valid representation of an integer.
Since 4.05
valread_int : unit->int
Same as read_int_opt , but raise Failure"int_of_string" instead of returning None .
valread_float_opt : unit->floatoption
Flush standard output, then read one line from standard input and convert it to a floating-point number.
Return None if the line read is not a valid representation of a floating-point number.
Since 4.05
valread_float : unit->float
Same as read_float_opt , but raise Failure"float_of_string" instead of returning None .
Generaloutputfunctionstypeopen_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 .
valopen_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 truncated to zero length if it already exists. It is created if it
does not already exists.
valopen_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 .
valopen_out_gen : open_flaglist->int->string->out_channelopen_out_genmodepermfilename 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.
valflush : 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.
valflush_all : unit->unit
Flush all open output channels; ignore errors.
valoutput_char : out_channel->char->unit
Write the character on the given output channel.
valoutput_string : out_channel->string->unit
Write the string on the given output channel.
valoutput_bytes : out_channel->bytes->unit
Write the byte sequence on the given output channel.
Since 4.02
valoutput : out_channel->bytes->int->int->unitoutputocbufposlen writes len characters from byte sequence buf , starting at offset pos , to the
given output channel oc .
RaisesInvalid_argument if pos and len do not designate a valid range of buf .
valoutput_substring : out_channel->string->int->int->unit
Same as output but take a string as argument instead of a byte sequence.
Since 4.02
valoutput_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.
valoutput_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 input_binary_int function.
The format is compatible across all machines for a given version of OCaml.
valoutput_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 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.
valseek_out : out_channel->int->unitseek_outchanpos 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.
valpos_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 particular, 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.
valout_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.
valclose_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.
valclose_out_noerr : out_channel->unit
Same as close_out , but ignore all errors.
valset_binary_mode_out : out_channel->bool->unitset_binary_mode_outoctrue sets the channel oc to binary mode: no translations take place during output.
set_binary_mode_outocfalse 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.
Generalinputfunctionsvalopen_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.
valopen_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 .
valopen_in_gen : open_flaglist->int->string->in_channelopen_in_genmodepermfilename opens the named file for reading, as described 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.
valinput_char : in_channel->char
Read one character from the given input channel.
RaisesEnd_of_file if there are no more characters to read.
valinput_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.
RaisesEnd_of_file if the end of the file is reached at the beginning of line.
valinput : in_channel->bytes->int->int->intinputicbufposlen 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 .
valreally_input : in_channel->bytes->int->int->unitreally_inputicbufposlen reads len characters from channel ic , storing them in byte sequence buf ,
starting at character number pos .
RaisesEnd_of_file if the end of file is reached before len characters have been read.
RaisesInvalid_argument if pos and len do not designate a valid range of buf .
valreally_input_string : in_channel->int->stringreally_input_stringiclen reads len characters from channel ic and returns them in a new string.
Since 4.02
RaisesEnd_of_file if the end of file is reached before len characters have been read.
valinput_byte : in_channel->int
Same as input_char , but return the 8-bit integer representing the character.
RaisesEnd_of_file if the end of file was reached.
valinput_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 .
RaisesEnd_of_file if the end of file was reached while reading the integer.
valinput_value : in_channel->'a
Read the representation of a structured value, as produced by 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.
valseek_in : in_channel->int->unitseek_inchanpos 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.
valpos_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.
valin_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.
valclose_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.
valclose_in_noerr : in_channel->unit
Same as close_in , but ignore all errors.
valset_binary_mode_in : in_channel->bool->unitset_binary_mode_inictrue sets the channel ic to binary mode: no translations take place during input.
set_binary_mode_outicfalse 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.
OperationsonlargefilesmoduleLargeFile:sigend
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 .
Referencestype'aref = {
mutable contents : 'a ;
}
The type of references (mutable indirection cells) containing a value of type 'a .
valref : 'a->'aref
Return a fresh reference containing the given value.
val(!) : 'aref->'a!r returns the current contents of reference r . Equivalent to funr->r.contents . Unary operator,
see Ocaml_operators for more information.
val(:=) : 'aref->'a->unitr:=a stores the value of a in reference r . Equivalent to funrv->r.contents<-v .
Right-associative operator, see Ocaml_operators for more information.
valincr : intref->unit
Increment the integer contained in the given reference. Equivalent to funr->r:=succ!r .
valdecr : intref->unit
Decrement the integer contained in the given reference. Equivalent to funr->r:=pred!r .
Resulttypetype('a,'b)result =
| Ok of'a
| Error of'bSince 4.03
Operationsonformatstrings
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 .
Format strings have a general and highly polymorphic type ('a,'b,'c,'d,'e,'f)format6 . 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,'d,'e,'f)format6 = ('a,'b,'c,'d,'e,'f)CamlinternalFormatBasics.format6type('a,'b,'c,'d)format4 = ('a,'b,'c,'c,'c,'d)format6type('a,'b,'c)format = ('a,'b,'c,'c)format4valstring_of_format : ('a,'b,'c,'d,'e,'f)format6->string
Converts a format string into a string.
valformat_of_string : ('a,'b,'c,'d,'e,'f)format6->('a,'b,'c,'d,'e,'f)format6format_of_strings 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)format6f1^^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 .
Right-associative operator, see Ocaml_operators for more information.
Programterminationvalexit : 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 . The callbacks registered with Domain.at_exit are called followed by those registered with
at_exit .
An implicit exit0 is performed each time a program terminates normally. An implicit exit2 is performed
if the program terminates early because of an uncaught exception.
valat_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.
StandardlibrarymodulesmoduleArg:(moduleStdlib__Arg)moduleArray:(moduleStdlib__Array)moduleArrayLabels:(moduleStdlib__ArrayLabels)moduleAtomic:(moduleStdlib__Atomic)moduleBigarray:(moduleStdlib__Bigarray)moduleBool:(moduleStdlib__Bool)moduleBuffer:(moduleStdlib__Buffer)moduleBytes:(moduleStdlib__Bytes)moduleBytesLabels:(moduleStdlib__BytesLabels)moduleCallback:(moduleStdlib__Callback)moduleChar:(moduleStdlib__Char)moduleComplex:(moduleStdlib__Complex)moduleCondition:(moduleStdlib__Condition)moduleDigest:(moduleStdlib__Digest)moduleDomain:(moduleStdlib__Domain)Alertunstable. The Domain interface may change in incompatible ways in the future.
moduleDynarray:(moduleStdlib__Dynarray)moduleEffect:(moduleStdlib__Effect)Alertunstable. The Effect interface may change in incompatible ways in the future.
moduleEither:(moduleStdlib__Either)moduleEphemeron:(moduleStdlib__Ephemeron)moduleFilename:(moduleStdlib__Filename)moduleFloat:(moduleStdlib__Float)moduleFormat:(moduleStdlib__Format)moduleFun:(moduleStdlib__Fun)moduleGc:(moduleStdlib__Gc)moduleHashtbl:(moduleStdlib__Hashtbl)moduleIn_channel:(moduleStdlib__In_channel)moduleInt:(moduleStdlib__Int)moduleInt32:(moduleStdlib__Int32)moduleInt64:(moduleStdlib__Int64)moduleLazy:(moduleStdlib__Lazy)moduleLexing:(moduleStdlib__Lexing)moduleList:(moduleStdlib__List)moduleListLabels:(moduleStdlib__ListLabels)moduleMap:(moduleStdlib__Map)moduleMarshal:(moduleStdlib__Marshal)moduleMoreLabels:(moduleStdlib__MoreLabels)moduleMutex:(moduleStdlib__Mutex)moduleNativeint:(moduleStdlib__Nativeint)moduleObj:(moduleStdlib__Obj)moduleOo:(moduleStdlib__Oo)moduleOption:(moduleStdlib__Option)moduleOut_channel:(moduleStdlib__Out_channel)moduleParsing:(moduleStdlib__Parsing)modulePrintexc:(moduleStdlib__Printexc)modulePrintf:(moduleStdlib__Printf)moduleQueue:(moduleStdlib__Queue)moduleRandom:(moduleStdlib__Random)moduleResult:(moduleStdlib__Result)moduleScanf:(moduleStdlib__Scanf)moduleSemaphore:(moduleStdlib__Semaphore)moduleSeq:(moduleStdlib__Seq)moduleSet:(moduleStdlib__Set)moduleStack:(moduleStdlib__Stack)moduleStdLabels:(moduleStdlib__StdLabels)moduleString:(moduleStdlib__String)moduleStringLabels:(moduleStdlib__StringLabels)moduleSys:(moduleStdlib__Sys)moduleType:(moduleStdlib__Type)moduleUchar:(moduleStdlib__Uchar)moduleUnit:(moduleStdlib__Unit)moduleWeak:(moduleStdlib__Weak)
OCamldoc 2025-06-12 Stdlib(3o)
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