1Stdlib(3) OCaml library Stdlib(3)
2
6 Stdlib - The OCaml Standard library.
7
9 Module Stdlib
10
12 Module Stdlib
13 : sig end
14 The OCaml Standard library.
17 This module is automatically opened at the beginning of each compila‐
19 tion. All components of this module can therefore be referred by their
20 short name, without prefixing them by Stdlib .
21 In particular, it provides the basic operations over the built-in types
23 (numbers, booleans, byte sequences, strings, exceptions, references,
24 lists, arrays, input-output channels, ...) and the modules .
25 Exceptions
33 val raise : exn -> 'a
34 Raise the given exception value
36 val raise_notrace : exn -> 'a
40 A faster version raise which does not record the backtrace.
42 Since 4.02.0
45 val invalid_arg : string -> 'a
49 Raise exception Invalid_argument with the given string.
51 val failwith : string -> 'a
55 Raise exception Failure with the given string.
57 exception Exit
61 The Exit exception is not raised by any library function. It is pro‐
64 vided for use in your programs.
65 exception Match_failure of (string * int * int)
69 Exception raised when none of the cases of a pattern-matching apply.
72 The arguments are the location of the match keyword in the source code
73 (file name, line number, column number).
74 exception Assert_failure of (string * int * int)
78 Exception raised when an assertion fails. The arguments are the loca‐
81 tion of the assert keyword in the source code (file name, line number,
82 column number).
83 exception Invalid_argument of string
87 Exception raised by library functions to signal that the given argu‐
90 ments do not make sense. The string gives some information to the pro‐
91 grammer. As a general rule, this exception should not be caught, it de‐
92 notes a programming error and the code should be modified not to trig‐
93 ger it.
94 exception Failure of string
98 Exception raised by library functions to signal that they are undefined
101 on the given arguments. The string is meant to give some information to
102 the programmer; you must not pattern match on the string literal be‐
103 cause it may change in future versions (use Failure _ instead).
104 exception Not_found
108 Exception raised by search functions when the desired object could not
111 be found.
112 exception Out_of_memory
116 Exception raised by the garbage collector when there is insufficient
119 memory to complete the computation. (Not reliable for allocations on
120 the minor heap.)
121 exception Stack_overflow
125 Exception raised by the bytecode interpreter when the evaluation stack
128 reaches its maximal size. This often indicates infinite or excessively
129 deep recursion in the user's program.
130 Before 4.10, it was not fully implemented by the native-code compiler.
132 exception Sys_error of string
136 Exception raised by the input/output functions to report an operating
139 system error. The string is meant to give some information to the pro‐
140 grammer; you must not pattern match on the string literal because it
141 may change in future versions (use Sys_error _ instead).
142 exception End_of_file
146 Exception raised by input functions to signal that the end of file has
149 been reached.
150 exception Division_by_zero
154 Exception raised by integer division and remainder operations when
157 their second argument is zero.
158 exception Sys_blocked_io
162 A special case of Sys_error raised when no I/O is possible on a
165 non-blocking I/O channel.
166 exception Undefined_recursive_module of (string * int * int)
170 Exception raised when an ill-founded recursive module definition is
173 evaluated. The arguments are the location of the definition in the
174 source code (file name, line number, column number).
175 Comparisons
180 val (=) : 'a -> 'a -> bool
181 e1 = e2 tests for structural equality of e1 and e2 . Mutable struc‐
184 tures (e.g. references and arrays) are equal if and only if their cur‐
185 rent contents are structurally equal, even if the two mutable objects
186 are not the same physical object. Equality between functional values
187 raises Invalid_argument . Equality between cyclic data structures may
188 not terminate. Left-associative operator, see Ocaml_operators for more
189 information.
190 val (<>) : 'a -> 'a -> bool
194 Negation of (=) . Left-associative operator, see Ocaml_operators for
196 more information.
197 val (<) : 'a -> 'a -> bool
201 See (>=) . Left-associative operator, see Ocaml_operators for more in‐
203 formation.
204 val (>) : 'a -> 'a -> bool
208 See (>=) . Left-associative operator, see Ocaml_operators for more
210 information.
211 val (<=) : 'a -> 'a -> bool
215 See (>=) . Left-associative operator, see Ocaml_operators for more
217 information.
218 val (>=) : 'a -> 'a -> bool
222 Structural ordering functions. These functions coincide with the usual
224 orderings over integers, characters, strings, byte sequences and float‐
225 ing-point numbers, and extend them to a total ordering over all types.
226 The ordering is compatible with ( = ) . As in the case of ( = ) , muta‐
227 ble structures are compared by contents. Comparison between functional
228 values raises Invalid_argument . Comparison between cyclic structures
229 may not terminate. Left-associative operator, see Ocaml_operators for
230 more information.
231 val compare : 'a -> 'a -> int
235 compare x y returns 0 if x is equal to y , a negative integer if x is
238 less than y , and a positive integer if x is greater than y . The or‐
239 dering implemented by compare is compatible with the comparison predi‐
240 cates = , < and > defined above, with one difference on the treatment
241 of the float value nan . Namely, the comparison predicates treat nan
242 as different from any other float value, including itself; while com‐
243 pare treats nan as equal to itself and less than any other float value.
244 This treatment of nan ensures that compare defines a total ordering re‐
245 lation.
246 compare applied to functional values may raise Invalid_argument . com‐
249 pare applied to cyclic structures may not terminate.
250 The compare function can be used as the comparison function required by
252 the Set.Make and Map.Make functors, as well as the List.sort and Ar‐
253 ray.sort functions.
254 val min : 'a -> 'a -> 'a
258 Return the smaller of the two arguments. The result is unspecified if
260 one of the arguments contains the float value nan .
261 val max : 'a -> 'a -> 'a
265 Return the greater of the two arguments. The result is unspecified if
267 one of the arguments contains the float value nan .
268 val (==) : 'a -> 'a -> bool
272 e1 == e2 tests for physical equality of e1 and e2 . On mutable types
275 such as references, arrays, byte sequences, records with mutable fields
276 and objects with mutable instance variables, e1 == e2 is true if and
277 only if physical modification of e1 also affects e2 . On non-mutable
278 types, the behavior of ( == ) is implementation-dependent; however, it
279 is guaranteed that e1 == e2 implies compare e1 e2 = 0 . Left-associa‐
280 tive operator, see Ocaml_operators for more information.
281 val (!=) : 'a -> 'a -> bool
285 Negation of (==) . Left-associative operator, see Ocaml_operators for
287 more information.
288 Boolean operations
293 val not : bool -> bool
294 The boolean negation.
296 val (&&) : bool -> bool -> bool
300 The boolean 'and'. Evaluation is sequential, left-to-right: in e1 && e2
302 , e1 is evaluated first, and if it returns false , e2 is not evaluated
303 at all. Right-associative operator, see Ocaml_operators for more in‐
304 formation.
305 val (||) : bool -> bool -> bool
309 The boolean 'or'. Evaluation is sequential, left-to-right: in e1 || e2
311 , e1 is evaluated first, and if it returns true , e2 is not evaluated
312 at all. Right-associative operator, see Ocaml_operators for more in‐
313 formation.
314 Debugging
319 val __LOC__ : string
320 __LOC__ returns the location at which this expression appears in the
323 file currently being parsed by the compiler, with the standard error
324 format of OCaml: "File %S, line %d, characters %d-%d".
325 Since 4.02.0
328 val __FILE__ : string
332 __FILE__ returns the name of the file currently being parsed by the
335 compiler.
336 Since 4.02.0
339 val __LINE__ : int
343 __LINE__ returns the line number at which this expression appears in
346 the file currently being parsed by the compiler.
347 Since 4.02.0
350 val __MODULE__ : string
354 __MODULE__ returns the module name of the file being parsed by the com‐
357 piler.
358 Since 4.02.0
361 val __POS__ : string * int * int * int
365 __POS__ returns a tuple (file,lnum,cnum,enum) , corresponding to the
368 location at which this expression appears in the file currently being
369 parsed by the compiler. file is the current filename, lnum the line
370 number, cnum the character position in the line and enum the last char‐
371 acter position in the line.
372 Since 4.02.0
375 val __FUNCTION__ : string
379 __FUNCTION__ returns the name of the current function or method, in‐
382 cluding any enclosing modules or classes.
383 Since 4.12.0
386 val __LOC_OF__ : 'a -> string * 'a
390 __LOC_OF__ expr returns a pair (loc, expr) where loc is the location of
393 expr in the file currently being parsed by the compiler, with the stan‐
394 dard error format of OCaml: "File %S, line %d, characters %d-%d".
395 Since 4.02.0
398 val __LINE_OF__ : 'a -> int * 'a
402 __LINE_OF__ expr returns a pair (line, expr) , where line is the line
405 number at which the expression expr appears in the file currently being
406 parsed by the compiler.
407 Since 4.02.0
410 val __POS_OF__ : 'a -> (string * int * int * int) * 'a
414 __POS_OF__ expr returns a pair (loc,expr) , where loc is a tuple
417 (file,lnum,cnum,enum) corresponding to the location at which the ex‐
418 pression expr appears in the file currently being parsed by the com‐
419 piler. file is the current filename, lnum the line number, cnum the
420 character position in the line and enum the last character position in
421 the line.
422 Since 4.02.0
425 Composition operators
430 val (|>) : 'a -> ('a -> 'b) -> 'b
431 Reverse-application operator: x |> f |> g is exactly equivalent to g (f
433 (x)) . Left-associative operator, see Ocaml_operators for more infor‐
434 mation.
435 Since 4.01
438 val (@@) : ('a -> 'b) -> 'a -> 'b
442 Application operator: g @@ f @@ x is exactly equivalent to g (f (x)) .
444 Right-associative operator, see Ocaml_operators for more information.
445 Since 4.01
448 Integer arithmetic
453 Integers are Sys.int_size bits wide. All operations are taken modulo
454 2^ Sys.int_size . They do not fail on overflow.
455 val (~-) : int -> int
457 Unary negation. You can also write - e instead of ~- e . Unary opera‐
459 tor, see Ocaml_operators for more information.
460 val (~+) : int -> int
464 Unary addition. You can also write + e instead of ~+ e . Unary opera‐
466 tor, see Ocaml_operators for more information.
467 Since 3.12.0
470 val succ : int -> int
474 succ x is x + 1 .
477 val pred : int -> int
481 pred x is x - 1 .
484 val (+) : int -> int -> int
488 Integer addition. Left-associative operator, see Ocaml_operators for
490 more information.
491 val (-) : int -> int -> int
495 Integer subtraction. Left-associative operator, , see Ocaml_operators
497 for more information.
498 val ( * ) : int -> int -> int
502 Integer multiplication. Left-associative operator, see Ocaml_operators
504 for more information.
505 val (/) : int -> int -> int
509 Integer division. Integer division rounds the real quotient of its ar‐
511 guments towards zero. More precisely, if x >= 0 and y > 0 , x / y is
512 the greatest integer less than or equal to the real quotient of x by y
513 . Moreover, (- x) / y = x / (- y) = - (x / y) . Left-associative op‐
514 erator, see Ocaml_operators for more information.
515 Raises Division_by_zero if the second argument is 0.
518 val (mod) : int -> int -> int
522 Integer remainder. If y is not zero, the result of x mod y satisfies
524 the following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
525 abs(y) - 1 . If y = 0 , x mod y raises Division_by_zero . Note that x
526 mod y is negative only if x < 0 . Left-associative operator, see
527 Ocaml_operators for more information.
528 Raises Division_by_zero if y is zero.
531 val abs : int -> int
535 abs x is the absolute value of x . On min_int this is min_int itself
538 and thus remains negative.
539 val max_int : int
543 The greatest representable integer.
545 val min_int : int
549 The smallest representable integer.
551 Bitwise operations
556 val (land) : int -> int -> int
557 Bitwise logical and. Left-associative operator, see Ocaml_operators
559 for more information.
560 val (lor) : int -> int -> int
564 Bitwise logical or. Left-associative operator, see Ocaml_operators for
566 more information.
567 val (lxor) : int -> int -> int
571 Bitwise logical exclusive or. Left-associative operator, see Ocaml_op‐
573 erators for more information.
574 val lnot : int -> int
578 Bitwise logical negation.
580 val (lsl) : int -> int -> int
584 n lsl m shifts n to the left by m bits. The result is unspecified if m
587 < 0 or m > Sys.int_size . Right-associative operator, see Ocaml_opera‐
588 tors for more information.
589 val (lsr) : int -> int -> int
593 n lsr m shifts n to the right by m bits. This is a logical shift: ze‐
596 roes are inserted regardless of the sign of n . The result is unspeci‐
597 fied if m < 0 or m > Sys.int_size . Right-associative operator, see
598 Ocaml_operators for more information.
599 val (asr) : int -> int -> int
603 n asr m shifts n to the right by m bits. This is an arithmetic shift:
606 the sign bit of n is replicated. The result is unspecified if m < 0 or
607 m > Sys.int_size . Right-associative operator, see Ocaml_operators for
608 more information.
609 Floating-point arithmetic
614 OCaml's floating-point numbers follow the IEEE 754 standard, using dou‐
615 ble precision (64 bits) numbers. Floating-point operations never raise
616 an exception on overflow, underflow, division by zero, etc. Instead,
617 special IEEE numbers are returned as appropriate, such as infinity for
618 1.0 /. 0.0 , neg_infinity for -1.0 /. 0.0 , and nan ('not a number')
619 for 0.0 /. 0.0 . These special numbers then propagate through float‐
620 ing-point computations as expected: for instance, 1.0 /. infinity is
621 0.0 , basic arithmetic operations ( +. , -. , *. , /. ) with nan as
622 an argument return nan , ...
623 val (~-.) : float -> float
625 Unary negation. You can also write -. e instead of ~-. e . Unary oper‐
627 ator, see Ocaml_operators for more information.
628 val (~+.) : float -> float
632 Unary addition. You can also write +. e instead of ~+. e . Unary oper‐
634 ator, see Ocaml_operators for more information.
635 Since 3.12.0
638 val (+.) : float -> float -> float
642 Floating-point addition. Left-associative operator, see Ocaml_opera‐
644 tors for more information.
645 val (-.) : float -> float -> float
649 Floating-point subtraction. Left-associative operator, see Ocaml_oper‐
651 ators for more information.
652 val ( *. ) : float -> float -> float
656 Floating-point multiplication. Left-associative operator, see
658 Ocaml_operators for more information.
659 val (/.) : float -> float -> float
663 Floating-point division. Left-associative operator, see Ocaml_opera‐
665 tors for more information.
666 val ( ** ) : float -> float -> float
670 Exponentiation. Right-associative operator, see Ocaml_operators for
672 more information.
673 val sqrt : float -> float
677 Square root.
679 val exp : float -> float
683 Exponential.
685 val log : float -> float
689 Natural logarithm.
691 val log10 : float -> float
695 Base 10 logarithm.
697 val expm1 : float -> float
701 expm1 x computes exp x -. 1.0 , giving numerically-accurate results
704 even if x is close to 0.0 .
705 Since 3.12.0
708 val log1p : float -> float
712 log1p x computes log(1.0 +. x) (natural logarithm), giving numeri‐
715 cally-accurate results even if x is close to 0.0 .
716 Since 3.12.0
719 val cos : float -> float
723 Cosine. Argument is in radians.
725 val sin : float -> float
729 Sine. Argument is in radians.
731 val tan : float -> float
735 Tangent. Argument is in radians.
737 val acos : float -> float
741 Arc cosine. The argument must fall within the range [-1.0, 1.0] . Re‐
743 sult is in radians and is between 0.0 and pi .
744 val asin : float -> float
748 Arc sine. The argument must fall within the range [-1.0, 1.0] . Re‐
750 sult is in radians and is between -pi/2 and pi/2 .
751 val atan : float -> float
755 Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
757 val atan2 : float -> float -> float
761 atan2 y x returns the arc tangent of y /. x . The signs of x and y are
764 used to determine the quadrant of the result. Result is in radians and
765 is between -pi and pi .
766 val hypot : float -> float -> float
770 hypot x y returns sqrt(x *. x + y *. y) , that is, the length of the
773 hypotenuse of a right-angled triangle with sides of length x and y ,
774 or, equivalently, the distance of the point (x,y) to origin. If one of
775 x or y is infinite, returns infinity even if the other is nan .
776 Since 4.00.0
779 val cosh : float -> float
783 Hyperbolic cosine. Argument is in radians.
785 val sinh : float -> float
789 Hyperbolic sine. Argument is in radians.
791 val tanh : float -> float
795 Hyperbolic tangent. Argument is in radians.
797 val acosh : float -> float
801 Hyperbolic arc cosine. The argument must fall within the range [1.0,
803 inf] . Result is in radians and is between 0.0 and inf .
804 Since 4.13.0
807 val asinh : float -> float
811 Hyperbolic arc sine. The argument and result range over the entire
813 real line. Result is in radians.
814 Since 4.13.0
817 val atanh : float -> float
821 Hyperbolic arc tangent. The argument must fall within the range [-1.0,
823 1.0] . Result is in radians and ranges over the entire real line.
824 Since 4.13.0
827 val ceil : float -> float
831 Round above to an integer value. ceil f returns the least integer
833 value greater than or equal to f . The result is returned as a float.
834 val floor : float -> float
838 Round below to an integer value. floor f returns the greatest integer
840 value less than or equal to f . The result is returned as a float.
841 val abs_float : float -> float
845 abs_float f returns the absolute value of f .
848 val copysign : float -> float -> float
852 copysign x y returns a float whose absolute value is that of x and
855 whose sign is that of y . If x is nan , returns nan . If y is nan ,
856 returns either x or -. x , but it is not specified which.
857 Since 4.00.0
860 val mod_float : float -> float -> float
864 mod_float a b returns the remainder of a with respect to b . The re‐
867 turned value is a -. n *. b , where n is the quotient a /. b rounded
868 towards zero to an integer.
869 val frexp : float -> float * int
873 frexp f returns the pair of the significant and the exponent of f .
876 When f is zero, the significant x and the exponent n of f are equal to
877 zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
878 <= x < 1.0 .
879 val ldexp : float -> int -> float
883 ldexp x n returns x *. 2 ** n .
886 val modf : float -> float * float
890 modf f returns the pair of the fractional and integral part of f .
893 val float : int -> float
897 Same as float_of_int .
899 val float_of_int : int -> float
903 Convert an integer to floating-point.
905 val truncate : float -> int
909 Same as int_of_float .
911 val int_of_float : float -> int
915 Truncate the given floating-point number to an integer. The result is
917 unspecified if the argument is nan or falls outside the range of repre‐
918 sentable integers.
919 val infinity : float
923 Positive infinity.
925 val neg_infinity : float
929 Negative infinity.
931 val nan : float
935 A special floating-point value denoting the result of an undefined op‐
937 eration such as 0.0 /. 0.0 . Stands for 'not a number'. Any float‐
938 ing-point operation with nan as argument returns nan as result. As for
939 floating-point comparisons, = , < , <= , > and >= return false and <>
940 returns true if one or both of their arguments is nan .
941 val max_float : float
945 The largest positive finite value of type float .
947 val min_float : float
951 The smallest positive, non-zero, non-denormalized value of type float .
953 val epsilon_float : float
957 The difference between 1.0 and the smallest exactly representable
959 floating-point number greater than 1.0 .
960 type fpclass =
963 | FP_normal (* Normal number, none of the below
964 *)
965 | FP_subnormal (* Number very close to 0.0, has reduced precision
966 *)
967 | FP_zero (* Number is 0.0 or -0.0
968 *)
969 | FP_infinite (* Number is positive or negative infinity
970 *)
971 | FP_nan (* Not a number: result of an undefined operation
972 *)
973 The five classes of floating-point numbers, as determined by the clas‐
976 sify_float function.
977 val classify_float : float -> fpclass
981 Return the class of the given floating-point number: normal, subnormal,
983 zero, infinite, or not a number.
984 String operations
989 More string operations are provided in module String .
990 val (^) : string -> string -> string
992 String concatenation. Right-associative operator, see Ocaml_operators
994 for more information.
995 Raises Invalid_argument if the result is longer then than
998 Sys.max_string_length bytes.
999 Character operations
1004 More character operations are provided in module Char .
1005 val int_of_char : char -> int
1007 Return the ASCII code of the argument.
1009 val char_of_int : int -> char
1013 Return the character with the given ASCII code.
1015 Raises Invalid_argument if the argument is outside the range 0--255.
1018 Unit operations
1023 val ignore : 'a -> unit
1024 Discard the value of its argument and return () . For instance, ig‐
1026 nore(f x) discards the result of the side-effecting function f . It is
1027 equivalent to f x; () , except that the latter may generate a compiler
1028 warning; writing ignore(f x) instead avoids the warning.
1029 String conversion functions
1034 val string_of_bool : bool -> string
1035 Return the string representation of a boolean. As the returned values
1037 may be shared, the user should not modify them directly.
1038 val bool_of_string_opt : string -> bool option
1042 Convert the given string to a boolean.
1044 Return None if the string is not "true" or "false" .
1046 Since 4.05
1049 val bool_of_string : string -> bool
1053 Same as bool_of_string_opt , but raise Invalid_argument
1055 "bool_of_string" instead of returning None .
1056 val string_of_int : int -> string
1060 Return the string representation of an integer, in decimal.
1062 val int_of_string_opt : string -> int option
1066 Convert the given string to an integer. The string is read in decimal
1068 (by default, or if the string begins with 0u ), in hexadecimal (if it
1069 begins with 0x or 0X ), in octal (if it begins with 0o or 0O ), or in
1070 binary (if it begins with 0b or 0B ).
1071 The 0u prefix reads the input as an unsigned integer in the range [0,
1073 2*max_int+1] . If the input exceeds max_int it is converted to the
1074 signed integer min_int + input - max_int - 1 .
1075 The _ (underscore) character can appear anywhere in the string and is
1077 ignored.
1078 Return None if the given string is not a valid representation of an in‐
1080 teger, or if the integer represented exceeds the range of integers rep‐
1081 resentable in type int .
1082 Since 4.05
1085 val int_of_string : string -> int
1089 Same as int_of_string_opt , but raise Failure "int_of_string" instead
1091 of returning None .
1092 val string_of_float : float -> string
1096 Return a string representation of a floating-point number.
1098 This conversion can involve a loss of precision. For greater control
1100 over the manner in which the number is printed, see Printf .
1101 val float_of_string_opt : string -> float option
1105 Convert the given string to a float. The string is read in decimal (by
1107 default) or in hexadecimal (marked by 0x or 0X ).
1108 The format of decimal floating-point numbers is [-] dd.ddd (e|E) [+|-]
1110 dd , where d stands for a decimal digit.
1111 The format of hexadecimal floating-point numbers is [-] 0(x|X) hh.hhh
1113 (p|P) [+|-] dd , where h stands for an hexadecimal digit and d for a
1114 decimal digit.
1115 In both cases, at least one of the integer and fractional parts must be
1117 given; the exponent part is optional.
1118 The _ (underscore) character can appear anywhere in the string and is
1120 ignored.
1121 Depending on the execution platforms, other representations of float‐
1123 ing-point numbers can be accepted, but should not be relied upon.
1124 Return None if the given string is not a valid representation of a
1126 float.
1127 Since 4.05
1130 val float_of_string : string -> float
1134 Same as float_of_string_opt , but raise Failure "float_of_string" in‐
1136 stead of returning None .
1137 Pair operations
1142 val fst : 'a * 'b -> 'a
1143 Return the first component of a pair.
1145 val snd : 'a * 'b -> 'b
1149 Return the second component of a pair.
1151 List operations
1156 More list operations are provided in module List .
1157 val (@) : 'a list -> 'a list -> 'a list
1159 List concatenation. Not tail-recursive (length of the first argument).
1161 Right-associative operator, see Ocaml_operators for more information.
1162 Input/output
1167 Note: all input/output functions can raise Sys_error when the system
1168 calls they invoke fail.
1169 type in_channel
1171 The type of input channel.
1174 type out_channel
1177 The type of output channel.
1180 val stdin : in_channel
1184 The standard input for the process.
1186 val stdout : out_channel
1190 The standard output for the process.
1192 val stderr : out_channel
1196 The standard error output for the process.
1198 Output functions on standard output
1203 val print_char : char -> unit
1204 Print a character on standard output.
1206 val print_string : string -> unit
1210 Print a string on standard output.
1212 val print_bytes : bytes -> unit
1216 Print a byte sequence on standard output.
1218 Since 4.02.0
1221 val print_int : int -> unit
1225 Print an integer, in decimal, on standard output.
1227 val print_float : float -> unit
1231 Print a floating-point number, in decimal, on standard output.
1233 The conversion of the number to a string uses string_of_float and can
1235 involve a loss of precision.
1236 val print_endline : string -> unit
1240 Print a string, followed by a newline character, on standard output and
1242 flush standard output.
1243 val print_newline : unit -> unit
1247 Print a newline character on standard output, and flush standard out‐
1249 put. This can be used to simulate line buffering of standard output.
1250 Output functions on standard error
1255 val prerr_char : char -> unit
1256 Print a character on standard error.
1258 val prerr_string : string -> unit
1262 Print a string on standard error.
1264 val prerr_bytes : bytes -> unit
1268 Print a byte sequence on standard error.
1270 Since 4.02.0
1273 val prerr_int : int -> unit
1277 Print an integer, in decimal, on standard error.
1279 val prerr_float : float -> unit
1283 Print a floating-point number, in decimal, on standard error.
1285 The conversion of the number to a string uses string_of_float and can
1287 involve a loss of precision.
1288 val prerr_endline : string -> unit
1292 Print a string, followed by a newline character on standard error and
1294 flush standard error.
1295 val prerr_newline : unit -> unit
1299 Print a newline character on standard error, and flush standard error.
1301 Input functions on standard input
1306 val read_line : unit -> string
1307 Flush standard output, then read characters from standard input until a
1309 newline character is encountered.
1310 Return the string of all characters read, without the newline character
1312 at the end.
1313 Raises End_of_file if the end of the file is reached at the beginning
1316 of line.
1317 val read_int_opt : unit -> int option
1321 Flush standard output, then read one line from standard input and con‐
1323 vert it to an integer.
1324 Return None if the line read is not a valid representation of an inte‐
1326 ger.
1327 Since 4.05
1330 val read_int : unit -> int
1334 Same as read_int_opt , but raise Failure "int_of_string" instead of re‐
1336 turning None .
1337 val read_float_opt : unit -> float option
1341 Flush standard output, then read one line from standard input and con‐
1343 vert it to a floating-point number.
1344 Return None if the line read is not a valid representation of a float‐
1346 ing-point number.
1347 Since 4.05.0
1350 val read_float : unit -> float
1354 Same as read_float_opt , but raise Failure "float_of_string" instead of
1356 returning None .
1357 General output functions
1362 type open_flag =
1363 | Open_rdonly (* open for reading.
1364 *)
1365 | Open_wronly (* open for writing.
1366 *)
1367 | Open_append (* open for appending: always write at end of file.
1368 *)
1369 | Open_creat (* create the file if it does not exist.
1370 *)
1371 | Open_trunc (* empty the file if it already exists.
1372 *)
1373 | Open_excl (* fail if Open_creat and the file already exists.
1374 *)
1375 | Open_binary (* open in binary mode (no conversion).
1376 *)
1377 | Open_text (* open in text mode (may perform conversions).
1378 *)
1379 | Open_nonblock (* open in non-blocking mode.
1380 *)
1381 Opening modes for open_out_gen and open_in_gen .
1384 val open_out : string -> out_channel
1388 Open the named file for writing, and return a new output channel on
1390 that file, positioned at the beginning of the file. The file is trun‐
1391 cated to zero length if it already exists. It is created if it does not
1392 already exists.
1393 val open_out_bin : string -> out_channel
1397 Same as open_out , but the file is opened in binary mode, so that no
1399 translation takes place during writes. On operating systems that do not
1400 distinguish between text mode and binary mode, this function behaves
1401 like open_out .
1402 val open_out_gen : open_flag list -> int -> string -> out_channel
1406 open_out_gen mode perm filename opens the named file for writing, as
1409 described above. The extra argument mode specifies the opening mode.
1410 The extra argument perm specifies the file permissions, in case the
1411 file must be created. open_out and open_out_bin are special cases of
1412 this function.
1413 val flush : out_channel -> unit
1417 Flush the buffer associated with the given output channel, performing
1419 all pending writes on that channel. Interactive programs must be care‐
1420 ful about flushing standard output and standard error at the right
1421 time.
1422 val flush_all : unit -> unit
1426 Flush all open output channels; ignore errors.
1428 val output_char : out_channel -> char -> unit
1432 Write the character on the given output channel.
1434 val output_string : out_channel -> string -> unit
1438 Write the string on the given output channel.
1440 val output_bytes : out_channel -> bytes -> unit
1444 Write the byte sequence on the given output channel.
1446 Since 4.02.0
1449 val output : out_channel -> bytes -> int -> int -> unit
1453 output oc buf pos len writes len characters from byte sequence buf ,
1456 starting at offset pos , to the given output channel oc .
1457 Raises Invalid_argument if pos and len do not designate a valid range
1460 of buf .
1461 val output_substring : out_channel -> string -> int -> int -> unit
1465 Same as output but take a string as argument instead of a byte se‐
1467 quence.
1468 Since 4.02.0
1471 val output_byte : out_channel -> int -> unit
1475 Write one 8-bit integer (as the single character with that code) on the
1477 given output channel. The given integer is taken modulo 256.
1478 val output_binary_int : out_channel -> int -> unit
1482 Write one integer in binary format (4 bytes, big-endian) on the given
1484 output channel. The given integer is taken modulo 2^32. The only re‐
1485 liable way to read it back is through the input_binary_int function.
1486 The format is compatible across all machines for a given version of
1487 OCaml.
1488 val output_value : out_channel -> 'a -> unit
1492 Write the representation of a structured value of any type to a chan‐
1494 nel. Circularities and sharing inside the value are detected and pre‐
1495 served. The object can be read back, by the function input_value . See
1496 the description of module Marshal for more information. output_value
1497 is equivalent to Marshal.to_channel with an empty list of flags.
1498 val seek_out : out_channel -> int -> unit
1502 seek_out chan pos sets the current writing position to pos for channel
1505 chan . This works only for regular files. On files of other kinds (such
1506 as terminals, pipes and sockets), the behavior is unspecified.
1507 val pos_out : out_channel -> int
1511 Return the current writing position for the given channel. Does not
1513 work on channels opened with the Open_append flag (returns unspecified
1514 results). For files opened in text mode under Windows, the returned
1515 position is approximate (owing to end-of-line conversion); in particu‐
1516 lar, saving the current position with pos_out , then going back to this
1517 position using seek_out will not work. For this programming idiom to
1518 work reliably and portably, the file must be opened in binary mode.
1519 val out_channel_length : out_channel -> int
1523 Return the size (number of characters) of the regular file on which the
1525 given channel is opened. If the channel is opened on a file that is
1526 not a regular file, the result is meaningless.
1527 val close_out : out_channel -> unit
1531 Close the given channel, flushing all buffered write operations. Out‐
1533 put functions raise a Sys_error exception when they are applied to a
1534 closed output channel, except close_out and flush , which do nothing
1535 when applied to an already closed channel. Note that close_out may
1536 raise Sys_error if the operating system signals an error when flushing
1537 or closing.
1538 val close_out_noerr : out_channel -> unit
1542 Same as close_out , but ignore all errors.
1544 val set_binary_mode_out : out_channel -> bool -> unit
1548 set_binary_mode_out oc true sets the channel oc to binary mode: no
1551 translations take place during output. set_binary_mode_out oc false
1552 sets the channel oc to text mode: depending on the operating system,
1553 some translations may take place during output. For instance, under
1554 Windows, end-of-lines will be translated from \n to \r\n . This func‐
1555 tion has no effect under operating systems that do not distinguish be‐
1556 tween text mode and binary mode.
1557 General input functions
1562 val open_in : string -> in_channel
1563 Open the named file for reading, and return a new input channel on that
1565 file, positioned at the beginning of the file.
1566 val open_in_bin : string -> in_channel
1570 Same as open_in , but the file is opened in binary mode, so that no
1572 translation takes place during reads. On operating systems that do not
1573 distinguish between text mode and binary mode, this function behaves
1574 like open_in .
1575 val open_in_gen : open_flag list -> int -> string -> in_channel
1579 open_in_gen mode perm filename opens the named file for reading, as de‐
1582 scribed above. The extra arguments mode and perm specify the opening
1583 mode and file permissions. open_in and open_in_bin are special cases
1584 of this function.
1585 val input_char : in_channel -> char
1589 Read one character from the given input channel.
1591 Raises End_of_file if there are no more characters to read.
1594 val input_line : in_channel -> string
1598 Read characters from the given input channel, until a newline character
1600 is encountered. Return the string of all characters read, without the
1601 newline character at the end.
1602 Raises End_of_file if the end of the file is reached at the beginning
1605 of line.
1606 val input : in_channel -> bytes -> int -> int -> int
1610 input ic buf pos len reads up to len characters from the given channel
1613 ic , storing them in byte sequence buf , starting at character number
1614 pos . It returns the actual number of characters read, between 0 and
1615 len (inclusive). A return value of 0 means that the end of file was
1616 reached. A return value between 0 and len exclusive means that not all
1617 requested len characters were read, either because no more characters
1618 were available at that time, or because the implementation found it
1619 convenient to do a partial read; input must be called again to read the
1620 remaining characters, if desired. (See also really_input for reading
1621 exactly len characters.) Exception Invalid_argument "input" is raised
1622 if pos and len do not designate a valid range of buf .
1623 val really_input : in_channel -> bytes -> int -> int -> unit
1627 really_input ic buf pos len reads len characters from channel ic ,
1630 storing them in byte sequence buf , starting at character number pos .
1631 Raises End_of_file if the end of file is reached before len characters
1634 have been read.
1635 Raises Invalid_argument if pos and len do not designate a valid range
1638 of buf .
1639 val really_input_string : in_channel -> int -> string
1643 really_input_string ic len reads len characters from channel ic and re‐
1646 turns them in a new string.
1647 Since 4.02.0
1650 Raises End_of_file if the end of file is reached before len characters
1653 have been read.
1654 val input_byte : in_channel -> int
1658 Same as input_char , but return the 8-bit integer representing the
1660 character.
1661 Raises End_of_file if the end of file was reached.
1664 val input_binary_int : in_channel -> int
1668 Read an integer encoded in binary format (4 bytes, big-endian) from the
1670 given input channel. See output_binary_int .
1671 Raises End_of_file if the end of file was reached while reading the in‐
1674 teger.
1675 val input_value : in_channel -> 'a
1679 Read the representation of a structured value, as produced by out‐
1681 put_value , and return the corresponding value. This function is iden‐
1682 tical to Marshal.from_channel ; see the description of module Marshal
1683 for more information, in particular concerning the lack of type safety.
1684 val seek_in : in_channel -> int -> unit
1688 seek_in chan pos sets the current reading position to pos for channel
1691 chan . This works only for regular files. On files of other kinds, the
1692 behavior is unspecified.
1693 val pos_in : in_channel -> int
1697 Return the current reading position for the given channel. For files
1699 opened in text mode under Windows, the returned position is approximate
1700 (owing to end-of-line conversion); in particular, saving the current
1701 position with pos_in , then going back to this position using seek_in
1702 will not work. For this programming idiom to work reliably and
1703 portably, the file must be opened in binary mode.
1704 val in_channel_length : in_channel -> int
1708 Return the size (number of characters) of the regular file on which the
1710 given channel is opened. If the channel is opened on a file that is
1711 not a regular file, the result is meaningless. The returned size does
1712 not take into account the end-of-line translations that can be per‐
1713 formed when reading from a channel opened in text mode.
1714 val close_in : in_channel -> unit
1718 Close the given channel. Input functions raise a Sys_error exception
1720 when they are applied to a closed input channel, except close_in ,
1721 which does nothing when applied to an already closed channel.
1722 val close_in_noerr : in_channel -> unit
1726 Same as close_in , but ignore all errors.
1728 val set_binary_mode_in : in_channel -> bool -> unit
1732 set_binary_mode_in ic true sets the channel ic to binary mode: no
1735 translations take place during input. set_binary_mode_out ic false
1736 sets the channel ic to text mode: depending on the operating system,
1737 some translations may take place during input. For instance, under
1738 Windows, end-of-lines will be translated from \r\n to \n . This func‐
1739 tion has no effect under operating systems that do not distinguish be‐
1740 tween text mode and binary mode.
1741 Operations on large files
1746 module LargeFile : sig end
1747 Operations on large files. This sub-module provides 64-bit variants of
1750 the channel functions that manipulate file positions and file sizes.
1751 By representing positions and sizes by 64-bit integers (type int64 )
1752 instead of regular integers (type int ), these alternate functions al‐
1753 low operating on files whose sizes are greater than max_int .
1754 References
1759 type 'a ref = {
1760 mutable contents : 'a ;
1762 }
1763 The type of references (mutable indirection cells) containing a value
1766 of type 'a .
1767 val ref : 'a -> 'a ref
1771 Return a fresh reference containing the given value.
1773 val (!) : 'a ref -> 'a
1777 !r returns the current contents of reference r . Equivalent to fun r
1780 -> r.contents . Unary operator, see Ocaml_operators for more informa‐
1781 tion.
1782 val (:=) : 'a ref -> 'a -> unit
1786 r := a stores the value of a in reference r . Equivalent to fun r v ->
1789 r.contents <- v . Right-associative operator, see Ocaml_operators for
1790 more information.
1791 val incr : int ref -> unit
1795 Increment the integer contained in the given reference. Equivalent to
1797 fun r -> r := succ !r .
1798 val decr : int ref -> unit
1802 Decrement the integer contained in the given reference. Equivalent to
1804 fun r -> r := pred !r .
1805 Result type
1810 type ('a, 'b) result =
1811 | Ok of 'a
1812 | Error of 'b
1813 Since 4.03.0
1816 Operations on format strings
1821 Format strings are character strings with special lexical conventions
1822 that defines the functionality of formatted input/output functions.
1823 Format strings are used to read data with formatted input functions
1824 from module Scanf and to print data with formatted output functions
1825 from modules Printf and Format .
1826 Format strings are made of three kinds of entities:
1828 -conversions specifications, introduced by the special character '%'
1830 followed by one or more characters specifying what kind of argument to
1831 read or print,
1832 -formatting indications, introduced by the special character '@' fol‐
1834 lowed by one or more characters specifying how to read or print the ar‐
1835 gument,
1836 -plain characters that are regular characters with usual lexical con‐
1838 ventions. Plain characters specify string literals to be read in the
1839 input or printed in the output.
1840 There is an additional lexical rule to escape the special characters
1842 '%' and '@' in format strings: if a special character follows a '%'
1843 character, it is treated as a plain character. In other words, "%%" is
1844 considered as a plain '%' and "%@" as a plain '@' .
1845 For more information about conversion specifications and formatting in‐
1847 dications available, read the documentation of modules Scanf , Printf
1848 and Format .
1849 Format strings have a general and highly polymorphic type ('a, 'b, 'c,
1851 'd, 'e, 'f) format6 . The two simplified types, format and format4 be‐
1852 low are included for backward compatibility with earlier releases of
1853 OCaml.
1854 The meaning of format string type parameters is as follows:
1856 - 'a is the type of the parameters of the format for formatted output
1859 functions ( printf -style functions); 'a is the type of the values read
1860 by the format for formatted input functions ( scanf -style functions).
1861 - 'b is the type of input source for formatted input functions and the
1864 type of output target for formatted output functions. For printf
1865 -style functions from module Printf , 'b is typically out_channel ; for
1866 printf -style functions from module Format , 'b is typically For‐
1867 mat.formatter ; for scanf -style functions from module Scanf , 'b is
1868 typically Scanf.Scanning.in_channel .
1869 Type argument 'b is also the type of the first argument given to user's
1871 defined printing functions for %a and %t conversions, and user's de‐
1872 fined reading functions for %r conversion.
1873 - 'c is the type of the result of the %a and %t printing functions, and
1876 also the type of the argument transmitted to the first argument of
1877 kprintf -style functions or to the kscanf -style functions.
1878 - 'd is the type of parameters for the scanf -style functions.
1881 - 'e is the type of the receiver function for the scanf -style func‐
1884 tions.
1885 - 'f is the final result type of a formatted input/output function in‐
1888 vocation: for the printf -style functions, it is typically unit ; for
1889 the scanf -style functions, it is typically the result type of the re‐
1890 ceiver function.
1891 type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam‐
1894 linternalFormatBasics.format6
1895 type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
1900 type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
1905 val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
1911 Converts a format string into a string.
1913 val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
1917 'd, 'e, 'f) format6
1918 format_of_string s returns a format string read from the string literal
1921 s . Note: format_of_string can not convert a string argument that is
1922 not a literal. If you need this functionality, use the more general
1923 Scanf.format_from_string function.
1924 val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
1928 format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
1929 f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
1932 string that behaves as the concatenation of format strings f1 and f2 :
1933 in case of formatted output, it accepts arguments from f1 , then argu‐
1934 ments from f2 ; in case of formatted input, it returns results from f1
1935 , then results from f2 . Right-associative operator, see Ocaml_opera‐
1936 tors for more information.
1937 Program termination
1942 val exit : int -> 'a
1943 Terminate the process, returning the given status code to the operating
1945 system: usually 0 to indicate no errors, and a small positive integer
1946 to indicate failure. All open output channels are flushed with
1947 flush_all . The callbacks registered with Domain.at_exit are called
1948 followed by those registered with at_exit .
1949 An implicit exit 0 is performed each time a program terminates nor‐
1951 mally. An implicit exit 2 is performed if the program terminates early
1952 because of an uncaught exception.
1953 val at_exit : (unit -> unit) -> unit
1957 Register the given function to be called at program termination time.
1959 The functions registered with at_exit will be called when the program
1960 does any of the following:
1961 -executes exit
1963 -terminates, either normally or because of an uncaught exception
1966 -executes the C function caml_shutdown . The functions are called in
1968 'last in, first out' order: the function most recently added with
1969 at_exit is called first.
1970 Standard library modules
1976 module Arg : (module Stdlib__Arg)
1977 module Array : (module Stdlib__Array)
1982 module ArrayLabels : (module Stdlib__ArrayLabels)
1987 module Atomic : (module Stdlib__Atomic)
1992 module Bigarray : (module Stdlib__Bigarray)
1997 module Bool : (module Stdlib__Bool)
2002 module Buffer : (module Stdlib__Buffer)
2007 module Bytes : (module Stdlib__Bytes)
2012 module BytesLabels : (module Stdlib__BytesLabels)
2017 module Callback : (module Stdlib__Callback)
2022 module Char : (module Stdlib__Char)
2027 module Complex : (module Stdlib__Complex)
2032 module Condition : (module Stdlib__Condition)
2037 module Digest : (module Stdlib__Digest)
2042 module Domain : (module Stdlib__Domain)
2047 Alert unstable. The Domain interface may change in incompatible ways
2050 in the future.
2051 module Effect : (module Stdlib__Effect)
2054 Alert unstable. The Effect interface may change in incompatible ways
2057 in the future.
2058 module Either : (module Stdlib__Either)
2061 module Ephemeron : (module Stdlib__Ephemeron)
2066 module Filename : (module Stdlib__Filename)
2071 module Float : (module Stdlib__Float)
2076 module Format : (module Stdlib__Format)
2081 module Fun : (module Stdlib__Fun)
2086 module Gc : (module Stdlib__Gc)
2091 module Hashtbl : (module Stdlib__Hashtbl)
2096 module In_channel : (module Stdlib__In_channel)
2101 module Int : (module Stdlib__Int)
2106 module Int32 : (module Stdlib__Int32)
2111 module Int64 : (module Stdlib__Int64)
2116 module Lazy : (module Stdlib__Lazy)
2121 module Lexing : (module Stdlib__Lexing)
2126 module List : (module Stdlib__List)
2131 module ListLabels : (module Stdlib__ListLabels)
2136 module Map : (module Stdlib__Map)
2141 module Marshal : (module Stdlib__Marshal)
2146 module MoreLabels : (module Stdlib__MoreLabels)
2151 module Mutex : (module Stdlib__Mutex)
2156 module Nativeint : (module Stdlib__Nativeint)
2161 module Obj : (module Stdlib__Obj)
2166 module Oo : (module Stdlib__Oo)
2171 module Option : (module Stdlib__Option)
2176 module Out_channel : (module Stdlib__Out_channel)
2181 module Parsing : (module Stdlib__Parsing)
2186 module Printexc : (module Stdlib__Printexc)
2191 module Printf : (module Stdlib__Printf)
2196 module Queue : (module Stdlib__Queue)
2201 module Random : (module Stdlib__Random)
2206 module Result : (module Stdlib__Result)
2211 module Scanf : (module Stdlib__Scanf)
2216 module Semaphore : (module Stdlib__Semaphore)
2221 module Seq : (module Stdlib__Seq)
2226 module Set : (module Stdlib__Set)
2231 module Stack : (module Stdlib__Stack)
2236 module StdLabels : (module Stdlib__StdLabels)
2241 module String : (module Stdlib__String)
2246 module StringLabels : (module Stdlib__StringLabels)
2251 module Sys : (module Stdlib__Sys)
2256 module Uchar : (module Stdlib__Uchar)
2261 module Unit : (module Stdlib__Unit)
2266 module Weak : (module Stdlib__Weak)
2271OCamldoc 2023-07-20 Stdlib(3)