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 It 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 Deprecated.
311 (&&) should be used instead. Right-associative operator, see Ocaml_op‐
313 erators for more information.
314 val (||) : bool -> bool -> bool
318 The boolean 'or'. Evaluation is sequential, left-to-right: in e1 || e2
320 , e1 is evaluated first, and if it returns true , e2 is not evaluated
321 at all. Right-associative operator, see Ocaml_operators for more in‐
322 formation.
323 val (or) : bool -> bool -> bool
327 Deprecated.
329 (||) should be used instead. Right-associative operator, see Ocaml_op‐
331 erators for more information.
332 Debugging
337 val __LOC__ : string
338 __LOC__ returns the location at which this expression appears in the
341 file currently being parsed by the compiler, with the standard error
342 format of OCaml: "File %S, line %d, characters %d-%d".
343 Since 4.02.0
346 val __FILE__ : string
350 __FILE__ returns the name of the file currently being parsed by the
353 compiler.
354 Since 4.02.0
357 val __LINE__ : int
361 __LINE__ returns the line number at which this expression appears in
364 the file currently being parsed by the compiler.
365 Since 4.02.0
368 val __MODULE__ : string
372 __MODULE__ returns the module name of the file being parsed by the com‐
375 piler.
376 Since 4.02.0
379 val __POS__ : string * int * int * int
383 __POS__ returns a tuple (file,lnum,cnum,enum) , corresponding to the
386 location at which this expression appears in the file currently being
387 parsed by the compiler. file is the current filename, lnum the line
388 number, cnum the character position in the line and enum the last char‐
389 acter position in the line.
390 Since 4.02.0
393 val __FUNCTION__ : string
397 __FUNCTION__ returns the name of the current function or method, in‐
400 cluding any enclosing modules or classes.
401 Since 4.12.0
404 val __LOC_OF__ : 'a -> string * 'a
408 __LOC_OF__ expr returns a pair (loc, expr) where loc is the location of
411 expr in the file currently being parsed by the compiler, with the stan‐
412 dard error format of OCaml: "File %S, line %d, characters %d-%d".
413 Since 4.02.0
416 val __LINE_OF__ : 'a -> int * 'a
420 __LINE_OF__ expr returns a pair (line, expr) , where line is the line
423 number at which the expression expr appears in the file currently being
424 parsed by the compiler.
425 Since 4.02.0
428 val __POS_OF__ : 'a -> (string * int * int * int) * 'a
432 __POS_OF__ expr returns a pair (loc,expr) , where loc is a tuple
435 (file,lnum,cnum,enum) corresponding to the location at which the ex‐
436 pression expr appears in the file currently being parsed by the com‐
437 piler. file is the current filename, lnum the line number, cnum the
438 character position in the line and enum the last character position in
439 the line.
440 Since 4.02.0
443 Composition operators
448 val (|>) : 'a -> ('a -> 'b) -> 'b
449 Reverse-application operator: x |> f |> g is exactly equivalent to g (f
451 (x)) . Left-associative operator, see Ocaml_operators for more infor‐
452 mation.
453 Since 4.01
456 val (@@) : ('a -> 'b) -> 'a -> 'b
460 Application operator: g @@ f @@ x is exactly equivalent to g (f (x)) .
462 Right-associative operator, see Ocaml_operators for more information.
463 Since 4.01
466 Integer arithmetic
471 Integers are Sys.int_size bits wide. All operations are taken modulo
472 2^ Sys.int_size . They do not fail on overflow.
473 val (~-) : int -> int
475 Unary negation. You can also write - e instead of ~- e . Unary opera‐
477 tor, see Ocaml_operators for more information.
478 val (~+) : int -> int
482 Unary addition. You can also write + e instead of ~+ e . Unary opera‐
484 tor, see Ocaml_operators for more information.
485 Since 3.12.0
488 val succ : int -> int
492 succ x is x + 1 .
495 val pred : int -> int
499 pred x is x - 1 .
502 val (+) : int -> int -> int
506 Integer addition. Left-associative operator, see Ocaml_operators for
508 more information.
509 val (-) : int -> int -> int
513 Integer subtraction. Left-associative operator, , see Ocaml_operators
515 for more information.
516 val ( * ) : int -> int -> int
520 Integer multiplication. Left-associative operator, see Ocaml_operators
522 for more information.
523 val (/) : int -> int -> int
527 Integer division. Integer division rounds the real quotient of its ar‐
529 guments towards zero. More precisely, if x >= 0 and y > 0 , x / y is
530 the greatest integer less than or equal to the real quotient of x by y
531 . Moreover, (- x) / y = x / (- y) = - (x / y) . Left-associative op‐
532 erator, see Ocaml_operators for more information.
533 Raises Division_by_zero if the second argument is 0.
536 val (mod) : int -> int -> int
540 Integer remainder. If y is not zero, the result of x mod y satisfies
542 the following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
543 abs(y) - 1 . If y = 0 , x mod y raises Division_by_zero . Note that x
544 mod y is negative only if x < 0 . Left-associative operator, see
545 Ocaml_operators for more information.
546 Raises Division_by_zero if y is zero.
549 val abs : int -> int
553 Return the absolute value of the argument. Note that this may be nega‐
555 tive if the argument is min_int .
556 val max_int : int
560 The greatest representable integer.
562 val min_int : int
566 The smallest representable integer.
568 Bitwise operations
573 val (land) : int -> int -> int
574 Bitwise logical and. Left-associative operator, see Ocaml_operators
576 for more information.
577 val (lor) : int -> int -> int
581 Bitwise logical or. Left-associative operator, see Ocaml_operators for
583 more information.
584 val (lxor) : int -> int -> int
588 Bitwise logical exclusive or. Left-associative operator, see Ocaml_op‐
590 erators for more information.
591 val lnot : int -> int
595 Bitwise logical negation.
597 val (lsl) : int -> int -> int
601 n lsl m shifts n to the left by m bits. The result is unspecified if m
604 < 0 or m > Sys.int_size . Right-associative operator, see Ocaml_opera‐
605 tors for more information.
606 val (lsr) : int -> int -> int
610 n lsr m shifts n to the right by m bits. This is a logical shift: ze‐
613 roes are inserted regardless of the sign of n . The result is unspeci‐
614 fied if m < 0 or m > Sys.int_size . Right-associative operator, see
615 Ocaml_operators for more information.
616 val (asr) : int -> int -> int
620 n asr m shifts n to the right by m bits. This is an arithmetic shift:
623 the sign bit of n is replicated. The result is unspecified if m < 0 or
624 m > Sys.int_size . Right-associative operator, see Ocaml_operators for
625 more information.
626 Floating-point arithmetic
631 OCaml's floating-point numbers follow the IEEE 754 standard, using dou‐
632 ble precision (64 bits) numbers. Floating-point operations never raise
633 an exception on overflow, underflow, division by zero, etc. Instead,
634 special IEEE numbers are returned as appropriate, such as infinity for
635 1.0 /. 0.0 , neg_infinity for -1.0 /. 0.0 , and nan ('not a number')
636 for 0.0 /. 0.0 . These special numbers then propagate through float‐
637 ing-point computations as expected: for instance, 1.0 /. infinity is
638 0.0 , basic arithmetic operations ( +. , -. , *. , /. ) with nan as
639 an argument return nan , ...
640 val (~-.) : float -> float
642 Unary negation. You can also write -. e instead of ~-. e . Unary oper‐
644 ator, see Ocaml_operators for more information.
645 val (~+.) : float -> float
649 Unary addition. You can also write +. e instead of ~+. e . Unary oper‐
651 ator, see Ocaml_operators for more information.
652 Since 3.12.0
655 val (+.) : float -> float -> float
659 Floating-point addition. Left-associative operator, see Ocaml_opera‐
661 tors for more information.
662 val (-.) : float -> float -> float
666 Floating-point subtraction. Left-associative operator, see Ocaml_oper‐
668 ators for more information.
669 val ( *. ) : float -> float -> float
673 Floating-point multiplication. Left-associative operator, see
675 Ocaml_operators for more information.
676 val (/.) : float -> float -> float
680 Floating-point division. Left-associative operator, see Ocaml_opera‐
682 tors for more information.
683 val ( ** ) : float -> float -> float
687 Exponentiation. Right-associative operator, see Ocaml_operators for
689 more information.
690 val sqrt : float -> float
694 Square root.
696 val exp : float -> float
700 Exponential.
702 val log : float -> float
706 Natural logarithm.
708 val log10 : float -> float
712 Base 10 logarithm.
714 val expm1 : float -> float
718 expm1 x computes exp x -. 1.0 , giving numerically-accurate results
721 even if x is close to 0.0 .
722 Since 3.12.0
725 val log1p : float -> float
729 log1p x computes log(1.0 +. x) (natural logarithm), giving numeri‐
732 cally-accurate results even if x is close to 0.0 .
733 Since 3.12.0
736 val cos : float -> float
740 Cosine. Argument is in radians.
742 val sin : float -> float
746 Sine. Argument is in radians.
748 val tan : float -> float
752 Tangent. Argument is in radians.
754 val acos : float -> float
758 Arc cosine. The argument must fall within the range [-1.0, 1.0] . Re‐
760 sult is in radians and is between 0.0 and pi .
761 val asin : float -> float
765 Arc sine. The argument must fall within the range [-1.0, 1.0] . Re‐
767 sult is in radians and is between -pi/2 and pi/2 .
768 val atan : float -> float
772 Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
774 val atan2 : float -> float -> float
778 atan2 y x returns the arc tangent of y /. x . The signs of x and y are
781 used to determine the quadrant of the result. Result is in radians and
782 is between -pi and pi .
783 val hypot : float -> float -> float
787 hypot x y returns sqrt(x *. x + y *. y) , that is, the length of the
790 hypotenuse of a right-angled triangle with sides of length x and y ,
791 or, equivalently, the distance of the point (x,y) to origin. If one of
792 x or y is infinite, returns infinity even if the other is nan .
793 Since 4.00.0
796 val cosh : float -> float
800 Hyperbolic cosine. Argument is in radians.
802 val sinh : float -> float
806 Hyperbolic sine. Argument is in radians.
808 val tanh : float -> float
812 Hyperbolic tangent. Argument is in radians.
814 val acosh : float -> float
818 Hyperbolic arc cosine. The argument must fall within the range [1.0,
820 inf] . Result is in radians and is between 0.0 and inf .
821 Since 4.13.0
824 val asinh : float -> float
828 Hyperbolic arc sine. The argument and result range over the entire
830 real line. Result is in radians.
831 Since 4.13.0
834 val atanh : float -> float
838 Hyperbolic arc tangent. The argument must fall within the range [-1.0,
840 1.0] . Result is in radians and ranges over the entire real line.
841 Since 4.13.0
844 val ceil : float -> float
848 Round above to an integer value. ceil f returns the least integer
850 value greater than or equal to f . The result is returned as a float.
851 val floor : float -> float
855 Round below to an integer value. floor f returns the greatest integer
857 value less than or equal to f . The result is returned as a float.
858 val abs_float : float -> float
862 abs_float f returns the absolute value of f .
865 val copysign : float -> float -> float
869 copysign x y returns a float whose absolute value is that of x and
872 whose sign is that of y . If x is nan , returns nan . If y is nan ,
873 returns either x or -. x , but it is not specified which.
874 Since 4.00.0
877 val mod_float : float -> float -> float
881 mod_float a b returns the remainder of a with respect to b . The re‐
884 turned value is a -. n *. b , where n is the quotient a /. b rounded
885 towards zero to an integer.
886 val frexp : float -> float * int
890 frexp f returns the pair of the significant and the exponent of f .
893 When f is zero, the significant x and the exponent n of f are equal to
894 zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
895 <= x < 1.0 .
896 val ldexp : float -> int -> float
900 ldexp x n returns x *. 2 ** n .
903 val modf : float -> float * float
907 modf f returns the pair of the fractional and integral part of f .
910 val float : int -> float
914 Same as float_of_int .
916 val float_of_int : int -> float
920 Convert an integer to floating-point.
922 val truncate : float -> int
926 Same as int_of_float .
928 val int_of_float : float -> int
932 Truncate the given floating-point number to an integer. The result is
934 unspecified if the argument is nan or falls outside the range of repre‐
935 sentable integers.
936 val infinity : float
940 Positive infinity.
942 val neg_infinity : float
946 Negative infinity.
948 val nan : float
952 A special floating-point value denoting the result of an undefined op‐
954 eration such as 0.0 /. 0.0 . Stands for 'not a number'. Any float‐
955 ing-point operation with nan as argument returns nan as result. As for
956 floating-point comparisons, = , < , <= , > and >= return false and <>
957 returns true if one or both of their arguments is nan .
958 val max_float : float
962 The largest positive finite value of type float .
964 val min_float : float
968 The smallest positive, non-zero, non-denormalized value of type float .
970 val epsilon_float : float
974 The difference between 1.0 and the smallest exactly representable
976 floating-point number greater than 1.0 .
977 type fpclass =
980 | FP_normal (* Normal number, none of the below
981 *)
982 | FP_subnormal (* Number very close to 0.0, has reduced precision
983 *)
984 | FP_zero (* Number is 0.0 or -0.0
985 *)
986 | FP_infinite (* Number is positive or negative infinity
987 *)
988 | FP_nan (* Not a number: result of an undefined operation
989 *)
990 The five classes of floating-point numbers, as determined by the clas‐
993 sify_float function.
994 val classify_float : float -> fpclass
998 Return the class of the given floating-point number: normal, subnormal,
1000 zero, infinite, or not a number.
1001 String operations
1006 More string operations are provided in module String .
1007 val (^) : string -> string -> string
1009 String concatenation. Right-associative operator, see Ocaml_operators
1011 for more information.
1012 Raises Invalid_argument if the result is longer then than
1015 Sys.max_string_length bytes.
1016 Character operations
1021 More character operations are provided in module Char .
1022 val int_of_char : char -> int
1024 Return the ASCII code of the argument.
1026 val char_of_int : int -> char
1030 Return the character with the given ASCII code.
1032 Raises Invalid_argument if the argument is outside the range 0--255.
1035 Unit operations
1040 val ignore : 'a -> unit
1041 Discard the value of its argument and return () . For instance, ig‐
1043 nore(f x) discards the result of the side-effecting function f . It is
1044 equivalent to f x; () , except that the latter may generate a compiler
1045 warning; writing ignore(f x) instead avoids the warning.
1046 String conversion functions
1051 val string_of_bool : bool -> string
1052 Return the string representation of a boolean. As the returned values
1054 may be shared, the user should not modify them directly.
1055 val bool_of_string_opt : string -> bool option
1059 Convert the given string to a boolean.
1061 Return None if the string is not "true" or "false" .
1063 Since 4.05
1066 val bool_of_string : string -> bool
1070 Same as bool_of_string_opt , but raise Invalid_argument
1072 "bool_of_string" instead of returning None .
1073 val string_of_int : int -> string
1077 Return the string representation of an integer, in decimal.
1079 val int_of_string_opt : string -> int option
1083 Convert the given string to an integer. The string is read in decimal
1085 (by default, or if the string begins with 0u ), in hexadecimal (if it
1086 begins with 0x or 0X ), in octal (if it begins with 0o or 0O ), or in
1087 binary (if it begins with 0b or 0B ).
1088 The 0u prefix reads the input as an unsigned integer in the range [0,
1090 2*max_int+1] . If the input exceeds max_int it is converted to the
1091 signed integer min_int + input - max_int - 1 .
1092 The _ (underscore) character can appear anywhere in the string and is
1094 ignored.
1095 Return None if the given string is not a valid representation of an in‐
1097 teger, or if the integer represented exceeds the range of integers rep‐
1098 resentable in type int .
1099 Since 4.05
1102 val int_of_string : string -> int
1106 Same as int_of_string_opt , but raise Failure "int_of_string" instead
1108 of returning None .
1109 val string_of_float : float -> string
1113 Return a string representation of a floating-point number.
1115 This conversion can involve a loss of precision. For greater control
1117 over the manner in which the number is printed, see Printf .
1118 val float_of_string_opt : string -> float option
1122 Convert the given string to a float. The string is read in decimal (by
1124 default) or in hexadecimal (marked by 0x or 0X ).
1125 The format of decimal floating-point numbers is [-] dd.ddd (e|E) [+|-]
1127 dd , where d stands for a decimal digit.
1128 The format of hexadecimal floating-point numbers is [-] 0(x|X) hh.hhh
1130 (p|P) [+|-] dd , where h stands for an hexadecimal digit and d for a
1131 decimal digit.
1132 In both cases, at least one of the integer and fractional parts must be
1134 given; the exponent part is optional.
1135 The _ (underscore) character can appear anywhere in the string and is
1137 ignored.
1138 Depending on the execution platforms, other representations of float‐
1140 ing-point numbers can be accepted, but should not be relied upon.
1141 Return None if the given string is not a valid representation of a
1143 float.
1144 Since 4.05
1147 val float_of_string : string -> float
1151 Same as float_of_string_opt , but raise Failure "float_of_string" in‐
1153 stead of returning None .
1154 Pair operations
1159 val fst : 'a * 'b -> 'a
1160 Return the first component of a pair.
1162 val snd : 'a * 'b -> 'b
1166 Return the second component of a pair.
1168 List operations
1173 More list operations are provided in module List .
1174 val (@) : 'a list -> 'a list -> 'a list
1176 List concatenation. Not tail-recursive (length of the first argument).
1178 Right-associative operator, see Ocaml_operators for more information.
1179 Input/output
1184 Note: all input/output functions can raise Sys_error when the system
1185 calls they invoke fail.
1186 type in_channel
1188 The type of input channel.
1191 type out_channel
1194 The type of output channel.
1197 val stdin : in_channel
1201 The standard input for the process.
1203 val stdout : out_channel
1207 The standard output for the process.
1209 val stderr : out_channel
1213 The standard error output for the process.
1215 Output functions on standard output
1220 val print_char : char -> unit
1221 Print a character on standard output.
1223 val print_string : string -> unit
1227 Print a string on standard output.
1229 val print_bytes : bytes -> unit
1233 Print a byte sequence on standard output.
1235 Since 4.02.0
1238 val print_int : int -> unit
1242 Print an integer, in decimal, on standard output.
1244 val print_float : float -> unit
1248 Print a floating-point number, in decimal, on standard output.
1250 The conversion of the number to a string uses string_of_float and can
1252 involve a loss of precision.
1253 val print_endline : string -> unit
1257 Print a string, followed by a newline character, on standard output and
1259 flush standard output.
1260 val print_newline : unit -> unit
1264 Print a newline character on standard output, and flush standard out‐
1266 put. This can be used to simulate line buffering of standard output.
1267 Output functions on standard error
1272 val prerr_char : char -> unit
1273 Print a character on standard error.
1275 val prerr_string : string -> unit
1279 Print a string on standard error.
1281 val prerr_bytes : bytes -> unit
1285 Print a byte sequence on standard error.
1287 Since 4.02.0
1290 val prerr_int : int -> unit
1294 Print an integer, in decimal, on standard error.
1296 val prerr_float : float -> unit
1300 Print a floating-point number, in decimal, on standard error.
1302 The conversion of the number to a string uses string_of_float and can
1304 involve a loss of precision.
1305 val prerr_endline : string -> unit
1309 Print a string, followed by a newline character on standard error and
1311 flush standard error.
1312 val prerr_newline : unit -> unit
1316 Print a newline character on standard error, and flush standard error.
1318 Input functions on standard input
1323 val read_line : unit -> string
1324 Flush standard output, then read characters from standard input until a
1326 newline character is encountered.
1327 Return the string of all characters read, without the newline character
1329 at the end.
1330 Raises End_of_file if the end of the file is reached at the beginning
1333 of line.
1334 val read_int_opt : unit -> int option
1338 Flush standard output, then read one line from standard input and con‐
1340 vert it to an integer.
1341 Return None if the line read is not a valid representation of an inte‐
1343 ger.
1344 Since 4.05
1347 val read_int : unit -> int
1351 Same as read_int_opt , but raise Failure "int_of_string" instead of re‐
1353 turning None .
1354 val read_float_opt : unit -> float option
1358 Flush standard output, then read one line from standard input and con‐
1360 vert it to a floating-point number.
1361 Return None if the line read is not a valid representation of a float‐
1363 ing-point number.
1364 Since 4.05.0
1367 val read_float : unit -> float
1371 Same as read_float_opt , but raise Failure "float_of_string" instead of
1373 returning None .
1374 General output functions
1379 type open_flag =
1380 | Open_rdonly (* open for reading.
1381 *)
1382 | Open_wronly (* open for writing.
1383 *)
1384 | Open_append (* open for appending: always write at end of file.
1385 *)
1386 | Open_creat (* create the file if it does not exist.
1387 *)
1388 | Open_trunc (* empty the file if it already exists.
1389 *)
1390 | Open_excl (* fail if Open_creat and the file already exists.
1391 *)
1392 | Open_binary (* open in binary mode (no conversion).
1393 *)
1394 | Open_text (* open in text mode (may perform conversions).
1395 *)
1396 | Open_nonblock (* open in non-blocking mode.
1397 *)
1398 Opening modes for open_out_gen and open_in_gen .
1401 val open_out : string -> out_channel
1405 Open the named file for writing, and return a new output channel on
1407 that file, positioned at the beginning of the file. The file is trun‐
1408 cated to zero length if it already exists. It is created if it does not
1409 already exists.
1410 val open_out_bin : string -> out_channel
1414 Same as open_out , but the file is opened in binary mode, so that no
1416 translation takes place during writes. On operating systems that do not
1417 distinguish between text mode and binary mode, this function behaves
1418 like open_out .
1419 val open_out_gen : open_flag list -> int -> string -> out_channel
1423 open_out_gen mode perm filename opens the named file for writing, as
1426 described above. The extra argument mode specifies the opening mode.
1427 The extra argument perm specifies the file permissions, in case the
1428 file must be created. open_out and open_out_bin are special cases of
1429 this function.
1430 val flush : out_channel -> unit
1434 Flush the buffer associated with the given output channel, performing
1436 all pending writes on that channel. Interactive programs must be care‐
1437 ful about flushing standard output and standard error at the right
1438 time.
1439 val flush_all : unit -> unit
1443 Flush all open output channels; ignore errors.
1445 val output_char : out_channel -> char -> unit
1449 Write the character on the given output channel.
1451 val output_string : out_channel -> string -> unit
1455 Write the string on the given output channel.
1457 val output_bytes : out_channel -> bytes -> unit
1461 Write the byte sequence on the given output channel.
1463 Since 4.02.0
1466 val output : out_channel -> bytes -> int -> int -> unit
1470 output oc buf pos len writes len characters from byte sequence buf ,
1473 starting at offset pos , to the given output channel oc .
1474 Raises Invalid_argument if pos and len do not designate a valid range
1477 of buf .
1478 val output_substring : out_channel -> string -> int -> int -> unit
1482 Same as output but take a string as argument instead of a byte se‐
1484 quence.
1485 Since 4.02.0
1488 val output_byte : out_channel -> int -> unit
1492 Write one 8-bit integer (as the single character with that code) on the
1494 given output channel. The given integer is taken modulo 256.
1495 val output_binary_int : out_channel -> int -> unit
1499 Write one integer in binary format (4 bytes, big-endian) on the given
1501 output channel. The given integer is taken modulo 2^32. The only re‐
1502 liable way to read it back is through the input_binary_int function.
1503 The format is compatible across all machines for a given version of
1504 OCaml.
1505 val output_value : out_channel -> 'a -> unit
1509 Write the representation of a structured value of any type to a chan‐
1511 nel. Circularities and sharing inside the value are detected and pre‐
1512 served. The object can be read back, by the function input_value . See
1513 the description of module Marshal for more information. output_value
1514 is equivalent to Marshal.to_channel with an empty list of flags.
1515 val seek_out : out_channel -> int -> unit
1519 seek_out chan pos sets the current writing position to pos for channel
1522 chan . This works only for regular files. On files of other kinds (such
1523 as terminals, pipes and sockets), the behavior is unspecified.
1524 val pos_out : out_channel -> int
1528 Return the current writing position for the given channel. Does not
1530 work on channels opened with the Open_append flag (returns unspecified
1531 results). For files opened in text mode under Windows, the returned
1532 position is approximate (owing to end-of-line conversion); in particu‐
1533 lar, saving the current position with pos_out , then going back to this
1534 position using seek_out will not work. For this programming idiom to
1535 work reliably and portably, the file must be opened in binary mode.
1536 val out_channel_length : out_channel -> int
1540 Return the size (number of characters) of the regular file on which the
1542 given channel is opened. If the channel is opened on a file that is
1543 not a regular file, the result is meaningless.
1544 val close_out : out_channel -> unit
1548 Close the given channel, flushing all buffered write operations. Out‐
1550 put functions raise a Sys_error exception when they are applied to a
1551 closed output channel, except close_out and flush , which do nothing
1552 when applied to an already closed channel. Note that close_out may
1553 raise Sys_error if the operating system signals an error when flushing
1554 or closing.
1555 val close_out_noerr : out_channel -> unit
1559 Same as close_out , but ignore all errors.
1561 val set_binary_mode_out : out_channel -> bool -> unit
1565 set_binary_mode_out oc true sets the channel oc to binary mode: no
1568 translations take place during output. set_binary_mode_out oc false
1569 sets the channel oc to text mode: depending on the operating system,
1570 some translations may take place during output. For instance, under
1571 Windows, end-of-lines will be translated from \n to \r\n . This func‐
1572 tion has no effect under operating systems that do not distinguish be‐
1573 tween text mode and binary mode.
1574 General input functions
1579 val open_in : string -> in_channel
1580 Open the named file for reading, and return a new input channel on that
1582 file, positioned at the beginning of the file.
1583 val open_in_bin : string -> in_channel
1587 Same as open_in , but the file is opened in binary mode, so that no
1589 translation takes place during reads. On operating systems that do not
1590 distinguish between text mode and binary mode, this function behaves
1591 like open_in .
1592 val open_in_gen : open_flag list -> int -> string -> in_channel
1596 open_in_gen mode perm filename opens the named file for reading, as de‐
1599 scribed above. The extra arguments mode and perm specify the opening
1600 mode and file permissions. open_in and open_in_bin are special cases
1601 of this function.
1602 val input_char : in_channel -> char
1606 Read one character from the given input channel.
1608 Raises End_of_file if there are no more characters to read.
1611 val input_line : in_channel -> string
1615 Read characters from the given input channel, until a newline character
1617 is encountered. Return the string of all characters read, without the
1618 newline character at the end.
1619 Raises End_of_file if the end of the file is reached at the beginning
1622 of line.
1623 val input : in_channel -> bytes -> int -> int -> int
1627 input ic buf pos len reads up to len characters from the given channel
1630 ic , storing them in byte sequence buf , starting at character number
1631 pos . It returns the actual number of characters read, between 0 and
1632 len (inclusive). A return value of 0 means that the end of file was
1633 reached. A return value between 0 and len exclusive means that not all
1634 requested len characters were read, either because no more characters
1635 were available at that time, or because the implementation found it
1636 convenient to do a partial read; input must be called again to read the
1637 remaining characters, if desired. (See also really_input for reading
1638 exactly len characters.) Exception Invalid_argument "input" is raised
1639 if pos and len do not designate a valid range of buf .
1640 val really_input : in_channel -> bytes -> int -> int -> unit
1644 really_input ic buf pos len reads len characters from channel ic ,
1647 storing them in byte sequence buf , starting at character number pos .
1648 Raises End_of_file if the end of file is reached before len characters
1651 have been read.
1652 Raises Invalid_argument if pos and len do not designate a valid range
1655 of buf .
1656 val really_input_string : in_channel -> int -> string
1660 really_input_string ic len reads len characters from channel ic and re‐
1663 turns them in a new string.
1664 Since 4.02.0
1667 Raises End_of_file if the end of file is reached before len characters
1670 have been read.
1671 val input_byte : in_channel -> int
1675 Same as input_char , but return the 8-bit integer representing the
1677 character.
1678 Raises End_of_file if the end of file was reached.
1681 val input_binary_int : in_channel -> int
1685 Read an integer encoded in binary format (4 bytes, big-endian) from the
1687 given input channel. See output_binary_int .
1688 Raises End_of_file if the end of file was reached while reading the in‐
1691 teger.
1692 val input_value : in_channel -> 'a
1696 Read the representation of a structured value, as produced by out‐
1698 put_value , and return the corresponding value. This function is iden‐
1699 tical to Marshal.from_channel ; see the description of module Marshal
1700 for more information, in particular concerning the lack of type safety.
1701 val seek_in : in_channel -> int -> unit
1705 seek_in chan pos sets the current reading position to pos for channel
1708 chan . This works only for regular files. On files of other kinds, the
1709 behavior is unspecified.
1710 val pos_in : in_channel -> int
1714 Return the current reading position for the given channel. For files
1716 opened in text mode under Windows, the returned position is approximate
1717 (owing to end-of-line conversion); in particular, saving the current
1718 position with pos_in , then going back to this position using seek_in
1719 will not work. For this programming idiom to work reliably and
1720 portably, the file must be opened in binary mode.
1721 val in_channel_length : in_channel -> int
1725 Return the size (number of characters) of the regular file on which the
1727 given channel is opened. If the channel is opened on a file that is
1728 not a regular file, the result is meaningless. The returned size does
1729 not take into account the end-of-line translations that can be per‐
1730 formed when reading from a channel opened in text mode.
1731 val close_in : in_channel -> unit
1735 Close the given channel. Input functions raise a Sys_error exception
1737 when they are applied to a closed input channel, except close_in ,
1738 which does nothing when applied to an already closed channel.
1739 val close_in_noerr : in_channel -> unit
1743 Same as close_in , but ignore all errors.
1745 val set_binary_mode_in : in_channel -> bool -> unit
1749 set_binary_mode_in ic true sets the channel ic to binary mode: no
1752 translations take place during input. set_binary_mode_out ic false
1753 sets the channel ic to text mode: depending on the operating system,
1754 some translations may take place during input. For instance, under
1755 Windows, end-of-lines will be translated from \r\n to \n . This func‐
1756 tion has no effect under operating systems that do not distinguish be‐
1757 tween text mode and binary mode.
1758 Operations on large files
1763 module LargeFile : sig end
1764 Operations on large files. This sub-module provides 64-bit variants of
1767 the channel functions that manipulate file positions and file sizes.
1768 By representing positions and sizes by 64-bit integers (type int64 )
1769 instead of regular integers (type int ), these alternate functions al‐
1770 low operating on files whose sizes are greater than max_int .
1771 References
1776 type 'a ref = {
1777 mutable contents : 'a ;
1779 }
1780 The type of references (mutable indirection cells) containing a value
1783 of type 'a .
1784 val ref : 'a -> 'a ref
1788 Return a fresh reference containing the given value.
1790 val (!) : 'a ref -> 'a
1794 !r returns the current contents of reference r . Equivalent to fun r
1797 -> r.contents . Unary operator, see Ocaml_operators for more informa‐
1798 tion.
1799 val (:=) : 'a ref -> 'a -> unit
1803 r := a stores the value of a in reference r . Equivalent to fun r v ->
1806 r.contents <- v . Right-associative operator, see Ocaml_operators for
1807 more information.
1808 val incr : int ref -> unit
1812 Increment the integer contained in the given reference. Equivalent to
1814 fun r -> r := succ !r .
1815 val decr : int ref -> unit
1819 Decrement the integer contained in the given reference. Equivalent to
1821 fun r -> r := pred !r .
1822 Result type
1827 type ('a, 'b) result =
1828 | Ok of 'a
1829 | Error of 'b
1830 Since 4.03.0
1833 Operations on format strings
1838 Format strings are character strings with special lexical conventions
1839 that defines the functionality of formatted input/output functions.
1840 Format strings are used to read data with formatted input functions
1841 from module Scanf and to print data with formatted output functions
1842 from modules Printf and Format .
1843 Format strings are made of three kinds of entities:
1845 -conversions specifications, introduced by the special character '%'
1847 followed by one or more characters specifying what kind of argument to
1848 read or print,
1849 -formatting indications, introduced by the special character '@' fol‐
1851 lowed by one or more characters specifying how to read or print the ar‐
1852 gument,
1853 -plain characters that are regular characters with usual lexical con‐
1855 ventions. Plain characters specify string literals to be read in the
1856 input or printed in the output.
1857 There is an additional lexical rule to escape the special characters
1859 '%' and '@' in format strings: if a special character follows a '%'
1860 character, it is treated as a plain character. In other words, "%%" is
1861 considered as a plain '%' and "%@" as a plain '@' .
1862 For more information about conversion specifications and formatting in‐
1864 dications available, read the documentation of modules Scanf , Printf
1865 and Format .
1866 Format strings have a general and highly polymorphic type ('a, 'b, 'c,
1868 'd, 'e, 'f) format6 . The two simplified types, format and format4 be‐
1869 low are included for backward compatibility with earlier releases of
1870 OCaml.
1871 The meaning of format string type parameters is as follows:
1873 - 'a is the type of the parameters of the format for formatted output
1876 functions ( printf -style functions); 'a is the type of the values read
1877 by the format for formatted input functions ( scanf -style functions).
1878 - 'b is the type of input source for formatted input functions and the
1881 type of output target for formatted output functions. For printf
1882 -style functions from module Printf , 'b is typically out_channel ; for
1883 printf -style functions from module Format , 'b is typically For‐
1884 mat.formatter ; for scanf -style functions from module Scanf , 'b is
1885 typically Scanf.Scanning.in_channel .
1886 Type argument 'b is also the type of the first argument given to user's
1888 defined printing functions for %a and %t conversions, and user's de‐
1889 fined reading functions for %r conversion.
1890 - 'c is the type of the result of the %a and %t printing functions, and
1893 also the type of the argument transmitted to the first argument of
1894 kprintf -style functions or to the kscanf -style functions.
1895 - 'd is the type of parameters for the scanf -style functions.
1898 - 'e is the type of the receiver function for the scanf -style func‐
1901 tions.
1902 - 'f is the final result type of a formatted input/output function in‐
1905 vocation: for the printf -style functions, it is typically unit ; for
1906 the scanf -style functions, it is typically the result type of the re‐
1907 ceiver function.
1908 type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam‐
1911 linternalFormatBasics.format6
1912 type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
1917 type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
1922 val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
1928 Converts a format string into a string.
1930 val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
1934 'd, 'e, 'f) format6
1935 format_of_string s returns a format string read from the string literal
1938 s . Note: format_of_string can not convert a string argument that is
1939 not a literal. If you need this functionality, use the more general
1940 Scanf.format_from_string function.
1941 val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
1945 format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
1946 f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
1949 string that behaves as the concatenation of format strings f1 and f2 :
1950 in case of formatted output, it accepts arguments from f1 , then argu‐
1951 ments from f2 ; in case of formatted input, it returns results from f1
1952 , then results from f2 . Right-associative operator, see Ocaml_opera‐
1953 tors for more information.
1954 Program termination
1959 val exit : int -> 'a
1960 Terminate the process, returning the given status code to the operating
1962 system: usually 0 to indicate no errors, and a small positive integer
1963 to indicate failure. All open output channels are flushed with
1964 flush_all . An implicit exit 0 is performed each time a program termi‐
1965 nates normally. An implicit exit 2 is performed if the program termi‐
1966 nates early because of an uncaught exception.
1967 val at_exit : (unit -> unit) -> unit
1971 Register the given function to be called at program termination time.
1973 The functions registered with at_exit will be called when the program
1974 does any of the following:
1975 -executes exit
1977 -terminates, either normally or because of an uncaught exception
1980 -executes the C function caml_shutdown . The functions are called in
1982 'last in, first out' order: the function most recently added with
1983 at_exit is called first.
1984 Standard library modules
1990 module Arg : (module Stdlib__Arg)
1991 module Array : (module Stdlib__Array)
1996 module ArrayLabels : (module Stdlib__ArrayLabels)
2001 module Atomic : (module Stdlib__Atomic)
2006 module Bigarray : (module Stdlib__Bigarray)
2011 module Bool : (module Stdlib__Bool)
2016 module Buffer : (module Stdlib__Buffer)
2021 module Bytes : (module Stdlib__Bytes)
2026 module BytesLabels : (module Stdlib__BytesLabels)
2031 module Callback : (module Stdlib__Callback)
2036 module Char : (module Stdlib__Char)
2041 module Complex : (module Stdlib__Complex)
2046 module Digest : (module Stdlib__Digest)
2051 module Either : (module Stdlib__Either)
2056 module Ephemeron : (module Stdlib__Ephemeron)
2061 module Filename : (module Stdlib__Filename)
2066 module Float : (module Stdlib__Float)
2071 module Format : (module Stdlib__Format)
2076 module Fun : (module Stdlib__Fun)
2081 module Gc : (module Stdlib__Gc)
2086 module Genlex : (module Stdlib__Genlex)
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 Nativeint : (module Stdlib__Nativeint)
2156 module Obj : (module Stdlib__Obj)
2161 module Oo : (module Stdlib__Oo)
2166 module Option : (module Stdlib__Option)
2171 module Out_channel : (module Stdlib__Out_channel)
2176 module Parsing : (module Stdlib__Parsing)
2181 module Pervasives : (module Stdlib__Pervasives)
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 Seq : (module Stdlib__Seq)
2221 module Set : (module Stdlib__Set)
2226 module Stack : (module Stdlib__Stack)
2231 module StdLabels : (module Stdlib__StdLabels)
2236 module Stream : (module Stdlib__Stream)
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 2023-01-23 Stdlib(3)