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 ceil : float -> float
818 Round above to an integer value. ceil f returns the least integer
820 value greater than or equal to f . The result is returned as a float.
821 val floor : float -> float
825 Round below to an integer value. floor f returns the greatest integer
827 value less than or equal to f . The result is returned as a float.
828 val abs_float : float -> float
832 abs_float f returns the absolute value of f .
835 val copysign : float -> float -> float
839 copysign x y returns a float whose absolute value is that of x and
842 whose sign is that of y . If x is nan , returns nan . If y is nan ,
843 returns either x or -. x , but it is not specified which.
844 Since 4.00.0
847 val mod_float : float -> float -> float
851 mod_float a b returns the remainder of a with respect to b . The re‐
854 turned value is a -. n *. b , where n is the quotient a /. b rounded
855 towards zero to an integer.
856 val frexp : float -> float * int
860 frexp f returns the pair of the significant and the exponent of f .
863 When f is zero, the significant x and the exponent n of f are equal to
864 zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
865 <= x < 1.0 .
866 val ldexp : float -> int -> float
870 ldexp x n returns x *. 2 ** n .
873 val modf : float -> float * float
877 modf f returns the pair of the fractional and integral part of f .
880 val float : int -> float
884 Same as float_of_int .
886 val float_of_int : int -> float
890 Convert an integer to floating-point.
892 val truncate : float -> int
896 Same as int_of_float .
898 val int_of_float : float -> int
902 Truncate the given floating-point number to an integer. The result is
904 unspecified if the argument is nan or falls outside the range of repre‐
905 sentable integers.
906 val infinity : float
910 Positive infinity.
912 val neg_infinity : float
916 Negative infinity.
918 val nan : float
922 A special floating-point value denoting the result of an undefined op‐
924 eration such as 0.0 /. 0.0 . Stands for 'not a number'. Any float‐
925 ing-point operation with nan as argument returns nan as result. As for
926 floating-point comparisons, = , < , <= , > and >= return false and <>
927 returns true if one or both of their arguments is nan .
928 val max_float : float
932 The largest positive finite value of type float .
934 val min_float : float
938 The smallest positive, non-zero, non-denormalized value of type float .
940 val epsilon_float : float
944 The difference between 1.0 and the smallest exactly representable
946 floating-point number greater than 1.0 .
947 type fpclass =
950 | FP_normal (* Normal number, none of the below
951 *)
952 | FP_subnormal (* Number very close to 0.0, has reduced precision
953 *)
954 | FP_zero (* Number is 0.0 or -0.0
955 *)
956 | FP_infinite (* Number is positive or negative infinity
957 *)
958 | FP_nan (* Not a number: result of an undefined operation
959 *)
960 The five classes of floating-point numbers, as determined by the clas‐
963 sify_float function.
964 val classify_float : float -> fpclass
968 Return the class of the given floating-point number: normal, subnormal,
970 zero, infinite, or not a number.
971 String operations
976 More string operations are provided in module String .
977 val (^) : string -> string -> string
979 String concatenation. Right-associative operator, see Ocaml_operators
981 for more information.
982 Character operations
987 More character operations are provided in module Char .
988 val int_of_char : char -> int
990 Return the ASCII code of the argument.
992 val char_of_int : int -> char
996 Return the character with the given ASCII code.
998 Raises Invalid_argument if the argument is outside the range 0--255.
1001 Unit operations
1006 val ignore : 'a -> unit
1007 Discard the value of its argument and return () . For instance, ig‐
1009 nore(f x) discards the result of the side-effecting function f . It is
1010 equivalent to f x; () , except that the latter may generate a compiler
1011 warning; writing ignore(f x) instead avoids the warning.
1012 String conversion functions
1017 val string_of_bool : bool -> string
1018 Return the string representation of a boolean. As the returned values
1020 may be shared, the user should not modify them directly.
1021 val bool_of_string_opt : string -> bool option
1025 Convert the given string to a boolean.
1027 Return None if the string is not "true" or "false" .
1029 Since 4.05
1032 val bool_of_string : string -> bool
1036 Same as bool_of_string_opt , but raise Invalid_argument
1038 "bool_of_string" instead of returning None .
1039 val string_of_int : int -> string
1043 Return the string representation of an integer, in decimal.
1045 val int_of_string_opt : string -> int option
1049 Convert the given string to an integer. The string is read in decimal
1051 (by default, or if the string begins with 0u ), in hexadecimal (if it
1052 begins with 0x or 0X ), in octal (if it begins with 0o or 0O ), or in
1053 binary (if it begins with 0b or 0B ).
1054 The 0u prefix reads the input as an unsigned integer in the range [0,
1056 2*max_int+1] . If the input exceeds max_int it is converted to the
1057 signed integer min_int + input - max_int - 1 .
1058 The _ (underscore) character can appear anywhere in the string and is
1060 ignored.
1061 Return None if the given string is not a valid representation of an in‐
1063 teger, or if the integer represented exceeds the range of integers rep‐
1064 resentable in type int .
1065 Since 4.05
1068 val int_of_string : string -> int
1072 Same as int_of_string_opt , but raise Failure "int_of_string" instead
1074 of returning None .
1075 val string_of_float : float -> string
1079 Return the string representation of a floating-point number.
1081 val float_of_string_opt : string -> float option
1085 Convert the given string to a float. The string is read in decimal (by
1087 default) or in hexadecimal (marked by 0x or 0X ).
1088 The format of decimal floating-point numbers is [-] dd.ddd (e|E) [+|-]
1090 dd , where d stands for a decimal digit.
1091 The format of hexadecimal floating-point numbers is [-] 0(x|X) hh.hhh
1093 (p|P) [+|-] dd , where h stands for an hexadecimal digit and d for a
1094 decimal digit.
1095 In both cases, at least one of the integer and fractional parts must be
1097 given; the exponent part is optional.
1098 The _ (underscore) character can appear anywhere in the string and is
1100 ignored.
1101 Depending on the execution platforms, other representations of float‐
1103 ing-point numbers can be accepted, but should not be relied upon.
1104 Return None if the given string is not a valid representation of a
1106 float.
1107 Since 4.05
1110 val float_of_string : string -> float
1114 Same as float_of_string_opt , but raise Failure "float_of_string" in‐
1116 stead of returning None .
1117 Pair operations
1122 val fst : 'a * 'b -> 'a
1123 Return the first component of a pair.
1125 val snd : 'a * 'b -> 'b
1129 Return the second component of a pair.
1131 List operations
1136 More list operations are provided in module List .
1137 val (@) : 'a list -> 'a list -> 'a list
1139 List concatenation. Not tail-recursive (length of the first argument).
1141 Right-associative operator, see Ocaml_operators for more information.
1142 Input/output
1147 Note: all input/output functions can raise Sys_error when the system
1148 calls they invoke fail.
1149 type in_channel
1151 The type of input channel.
1154 type out_channel
1157 The type of output channel.
1160 val stdin : in_channel
1164 The standard input for the process.
1166 val stdout : out_channel
1170 The standard output for the process.
1172 val stderr : out_channel
1176 The standard error output for the process.
1178 Output functions on standard output
1183 val print_char : char -> unit
1184 Print a character on standard output.
1186 val print_string : string -> unit
1190 Print a string on standard output.
1192 val print_bytes : bytes -> unit
1196 Print a byte sequence on standard output.
1198 Since 4.02.0
1201 val print_int : int -> unit
1205 Print an integer, in decimal, on standard output.
1207 val print_float : float -> unit
1211 Print a floating-point number, in decimal, on standard output.
1213 val print_endline : string -> unit
1217 Print a string, followed by a newline character, on standard output and
1219 flush standard output.
1220 val print_newline : unit -> unit
1224 Print a newline character on standard output, and flush standard out‐
1226 put. This can be used to simulate line buffering of standard output.
1227 Output functions on standard error
1232 val prerr_char : char -> unit
1233 Print a character on standard error.
1235 val prerr_string : string -> unit
1239 Print a string on standard error.
1241 val prerr_bytes : bytes -> unit
1245 Print a byte sequence on standard error.
1247 Since 4.02.0
1250 val prerr_int : int -> unit
1254 Print an integer, in decimal, on standard error.
1256 val prerr_float : float -> unit
1260 Print a floating-point number, in decimal, on standard error.
1262 val prerr_endline : string -> unit
1266 Print a string, followed by a newline character on standard error and
1268 flush standard error.
1269 val prerr_newline : unit -> unit
1273 Print a newline character on standard error, and flush standard error.
1275 Input functions on standard input
1280 val read_line : unit -> string
1281 Flush standard output, then read characters from standard input until a
1283 newline character is encountered. Return the string of all characters
1284 read, without the newline character at the end.
1285 val read_int_opt : unit -> int option
1289 Flush standard output, then read one line from standard input and con‐
1291 vert it to an integer.
1292 Return None if the line read is not a valid representation of an inte‐
1294 ger.
1295 Since 4.05
1298 val read_int : unit -> int
1302 Same as read_int_opt , but raise Failure "int_of_string" instead of re‐
1304 turning None .
1305 val read_float_opt : unit -> float option
1309 Flush standard output, then read one line from standard input and con‐
1311 vert it to a floating-point number.
1312 Return None if the line read is not a valid representation of a float‐
1314 ing-point number.
1315 Since 4.05.0
1318 val read_float : unit -> float
1322 Same as read_float_opt , but raise Failure "float_of_string" instead of
1324 returning None .
1325 General output functions
1330 type open_flag =
1331 | Open_rdonly (* open for reading.
1332 *)
1333 | Open_wronly (* open for writing.
1334 *)
1335 | Open_append (* open for appending: always write at end of file.
1336 *)
1337 | Open_creat (* create the file if it does not exist.
1338 *)
1339 | Open_trunc (* empty the file if it already exists.
1340 *)
1341 | Open_excl (* fail if Open_creat and the file already exists.
1342 *)
1343 | Open_binary (* open in binary mode (no conversion).
1344 *)
1345 | Open_text (* open in text mode (may perform conversions).
1346 *)
1347 | Open_nonblock (* open in non-blocking mode.
1348 *)
1349 Opening modes for open_out_gen and open_in_gen .
1352 val open_out : string -> out_channel
1356 Open the named file for writing, and return a new output channel on
1358 that file, positioned at the beginning of the file. The file is trun‐
1359 cated to zero length if it already exists. It is created if it does not
1360 already exists.
1361 val open_out_bin : string -> out_channel
1365 Same as open_out , but the file is opened in binary mode, so that no
1367 translation takes place during writes. On operating systems that do not
1368 distinguish between text mode and binary mode, this function behaves
1369 like open_out .
1370 val open_out_gen : open_flag list -> int -> string -> out_channel
1374 open_out_gen mode perm filename opens the named file for writing, as
1377 described above. The extra argument mode specifies the opening mode.
1378 The extra argument perm specifies the file permissions, in case the
1379 file must be created. open_out and open_out_bin are special cases of
1380 this function.
1381 val flush : out_channel -> unit
1385 Flush the buffer associated with the given output channel, performing
1387 all pending writes on that channel. Interactive programs must be care‐
1388 ful about flushing standard output and standard error at the right
1389 time.
1390 val flush_all : unit -> unit
1394 Flush all open output channels; ignore errors.
1396 val output_char : out_channel -> char -> unit
1400 Write the character on the given output channel.
1402 val output_string : out_channel -> string -> unit
1406 Write the string on the given output channel.
1408 val output_bytes : out_channel -> bytes -> unit
1412 Write the byte sequence on the given output channel.
1414 Since 4.02.0
1417 val output : out_channel -> bytes -> int -> int -> unit
1421 output oc buf pos len writes len characters from byte sequence buf ,
1424 starting at offset pos , to the given output channel oc .
1425 Raises Invalid_argument if pos and len do not designate a valid range
1428 of buf .
1429 val output_substring : out_channel -> string -> int -> int -> unit
1433 Same as output but take a string as argument instead of a byte se‐
1435 quence.
1436 Since 4.02.0
1439 val output_byte : out_channel -> int -> unit
1443 Write one 8-bit integer (as the single character with that code) on the
1445 given output channel. The given integer is taken modulo 256.
1446 val output_binary_int : out_channel -> int -> unit
1450 Write one integer in binary format (4 bytes, big-endian) on the given
1452 output channel. The given integer is taken modulo 2^32. The only re‐
1453 liable way to read it back is through the input_binary_int function.
1454 The format is compatible across all machines for a given version of
1455 OCaml.
1456 val output_value : out_channel -> 'a -> unit
1460 Write the representation of a structured value of any type to a chan‐
1462 nel. Circularities and sharing inside the value are detected and pre‐
1463 served. The object can be read back, by the function input_value . See
1464 the description of module Marshal for more information. output_value
1465 is equivalent to Marshal.to_channel with an empty list of flags.
1466 val seek_out : out_channel -> int -> unit
1470 seek_out chan pos sets the current writing position to pos for channel
1473 chan . This works only for regular files. On files of other kinds (such
1474 as terminals, pipes and sockets), the behavior is unspecified.
1475 val pos_out : out_channel -> int
1479 Return the current writing position for the given channel. Does not
1481 work on channels opened with the Open_append flag (returns unspecified
1482 results). For files opened in text mode under Windows, the returned
1483 position is approximate (owing to end-of-line conversion); in particu‐
1484 lar, saving the current position with pos_out , then going back to this
1485 position using seek_out will not work. For this programming idiom to
1486 work reliably and portably, the file must be opened in binary mode.
1487 val out_channel_length : out_channel -> int
1491 Return the size (number of characters) of the regular file on which the
1493 given channel is opened. If the channel is opened on a file that is
1494 not a regular file, the result is meaningless.
1495 val close_out : out_channel -> unit
1499 Close the given channel, flushing all buffered write operations. Out‐
1501 put functions raise a Sys_error exception when they are applied to a
1502 closed output channel, except close_out and flush , which do nothing
1503 when applied to an already closed channel. Note that close_out may
1504 raise Sys_error if the operating system signals an error when flushing
1505 or closing.
1506 val close_out_noerr : out_channel -> unit
1510 Same as close_out , but ignore all errors.
1512 val set_binary_mode_out : out_channel -> bool -> unit
1516 set_binary_mode_out oc true sets the channel oc to binary mode: no
1519 translations take place during output. set_binary_mode_out oc false
1520 sets the channel oc to text mode: depending on the operating system,
1521 some translations may take place during output. For instance, under
1522 Windows, end-of-lines will be translated from \n to \r\n . This func‐
1523 tion has no effect under operating systems that do not distinguish be‐
1524 tween text mode and binary mode.
1525 General input functions
1530 val open_in : string -> in_channel
1531 Open the named file for reading, and return a new input channel on that
1533 file, positioned at the beginning of the file.
1534 val open_in_bin : string -> in_channel
1538 Same as open_in , but the file is opened in binary mode, so that no
1540 translation takes place during reads. On operating systems that do not
1541 distinguish between text mode and binary mode, this function behaves
1542 like open_in .
1543 val open_in_gen : open_flag list -> int -> string -> in_channel
1547 open_in_gen mode perm filename opens the named file for reading, as de‐
1550 scribed above. The extra arguments mode and perm specify the opening
1551 mode and file permissions. open_in and open_in_bin are special cases
1552 of this function.
1553 val input_char : in_channel -> char
1557 Read one character from the given input channel.
1559 Raises End_of_file if there are no more characters to read.
1562 val input_line : in_channel -> string
1566 Read characters from the given input channel, until a newline character
1568 is encountered. Return the string of all characters read, without the
1569 newline character at the end.
1570 Raises End_of_file if the end of the file is reached at the beginning
1573 of line.
1574 val input : in_channel -> bytes -> int -> int -> int
1578 input ic buf pos len reads up to len characters from the given channel
1581 ic , storing them in byte sequence buf , starting at character number
1582 pos . It returns the actual number of characters read, between 0 and
1583 len (inclusive). A return value of 0 means that the end of file was
1584 reached. A return value between 0 and len exclusive means that not all
1585 requested len characters were read, either because no more characters
1586 were available at that time, or because the implementation found it
1587 convenient to do a partial read; input must be called again to read the
1588 remaining characters, if desired. (See also really_input for reading
1589 exactly len characters.) Exception Invalid_argument "input" is raised
1590 if pos and len do not designate a valid range of buf .
1591 val really_input : in_channel -> bytes -> int -> int -> unit
1595 really_input ic buf pos len reads len characters from channel ic ,
1598 storing them in byte sequence buf , starting at character number pos .
1599 Raises End_of_file if the end of file is reached before len characters
1602 have been read.
1603 Raises Invalid_argument if pos and len do not designate a valid range
1606 of buf .
1607 val really_input_string : in_channel -> int -> string
1611 really_input_string ic len reads len characters from channel ic and re‐
1614 turns them in a new string.
1615 Since 4.02.0
1618 Raises End_of_file if the end of file is reached before len characters
1621 have been read.
1622 val input_byte : in_channel -> int
1626 Same as input_char , but return the 8-bit integer representing the
1628 character.
1629 Raises End_of_file if an end of file was reached.
1632 val input_binary_int : in_channel -> int
1636 Read an integer encoded in binary format (4 bytes, big-endian) from the
1638 given input channel. See output_binary_int .
1639 Raises End_of_file if an end of file was reached while reading the in‐
1642 teger.
1643 val input_value : in_channel -> 'a
1647 Read the representation of a structured value, as produced by out‐
1649 put_value , and return the corresponding value. This function is iden‐
1650 tical to Marshal.from_channel ; see the description of module Marshal
1651 for more information, in particular concerning the lack of type safety.
1652 val seek_in : in_channel -> int -> unit
1656 seek_in chan pos sets the current reading position to pos for channel
1659 chan . This works only for regular files. On files of other kinds, the
1660 behavior is unspecified.
1661 val pos_in : in_channel -> int
1665 Return the current reading position for the given channel. For files
1667 opened in text mode under Windows, the returned position is approximate
1668 (owing to end-of-line conversion); in particular, saving the current
1669 position with pos_in , then going back to this position using seek_in
1670 will not work. For this programming idiom to work reliably and
1671 portably, the file must be opened in binary mode.
1672 val in_channel_length : in_channel -> int
1676 Return the size (number of characters) of the regular file on which the
1678 given channel is opened. If the channel is opened on a file that is
1679 not a regular file, the result is meaningless. The returned size does
1680 not take into account the end-of-line translations that can be per‐
1681 formed when reading from a channel opened in text mode.
1682 val close_in : in_channel -> unit
1686 Close the given channel. Input functions raise a Sys_error exception
1688 when they are applied to a closed input channel, except close_in ,
1689 which does nothing when applied to an already closed channel.
1690 val close_in_noerr : in_channel -> unit
1694 Same as close_in , but ignore all errors.
1696 val set_binary_mode_in : in_channel -> bool -> unit
1700 set_binary_mode_in ic true sets the channel ic to binary mode: no
1703 translations take place during input. set_binary_mode_out ic false
1704 sets the channel ic to text mode: depending on the operating system,
1705 some translations may take place during input. For instance, under
1706 Windows, end-of-lines will be translated from \r\n to \n . This func‐
1707 tion has no effect under operating systems that do not distinguish be‐
1708 tween text mode and binary mode.
1709 Operations on large files
1714 module LargeFile : sig end
1715 Operations on large files. This sub-module provides 64-bit variants of
1718 the channel functions that manipulate file positions and file sizes.
1719 By representing positions and sizes by 64-bit integers (type int64 )
1720 instead of regular integers (type int ), these alternate functions al‐
1721 low operating on files whose sizes are greater than max_int .
1722 References
1727 type 'a ref = {
1728 mutable contents : 'a ;
1730 }
1731 The type of references (mutable indirection cells) containing a value
1734 of type 'a .
1735 val ref : 'a -> 'a ref
1739 Return a fresh reference containing the given value.
1741 val (!) : 'a ref -> 'a
1745 !r returns the current contents of reference r . Equivalent to fun r
1748 -> r.contents . Unary operator, see Ocaml_operators for more informa‐
1749 tion.
1750 val (:=) : 'a ref -> 'a -> unit
1754 r := a stores the value of a in reference r . Equivalent to fun r v ->
1757 r.contents <- v . Right-associative operator, see Ocaml_operators for
1758 more information.
1759 val incr : int ref -> unit
1763 Increment the integer contained in the given reference. Equivalent to
1765 fun r -> r := succ !r .
1766 val decr : int ref -> unit
1770 Decrement the integer contained in the given reference. Equivalent to
1772 fun r -> r := pred !r .
1773 Result type
1778 type ('a, 'b) result =
1779 | Ok of 'a
1780 | Error of 'b
1781 Since 4.03.0
1784 Operations on format strings
1789 Format strings are character strings with special lexical conventions
1790 that defines the functionality of formatted input/output functions.
1791 Format strings are used to read data with formatted input functions
1792 from module Scanf and to print data with formatted output functions
1793 from modules Printf and Format .
1794 Format strings are made of three kinds of entities:
1796 -conversions specifications, introduced by the special character '%'
1798 followed by one or more characters specifying what kind of argument to
1799 read or print,
1800 -formatting indications, introduced by the special character '@' fol‐
1802 lowed by one or more characters specifying how to read or print the ar‐
1803 gument,
1804 -plain characters that are regular characters with usual lexical con‐
1806 ventions. Plain characters specify string literals to be read in the
1807 input or printed in the output.
1808 There is an additional lexical rule to escape the special characters
1810 '%' and '@' in format strings: if a special character follows a '%'
1811 character, it is treated as a plain character. In other words, "%%" is
1812 considered as a plain '%' and "%@" as a plain '@' .
1813 For more information about conversion specifications and formatting in‐
1815 dications available, read the documentation of modules Scanf , Printf
1816 and Format .
1817 Format strings have a general and highly polymorphic type ('a, 'b, 'c,
1819 'd, 'e, 'f) format6 . The two simplified types, format and format4 be‐
1820 low are included for backward compatibility with earlier releases of
1821 OCaml.
1822 The meaning of format string type parameters is as follows:
1824 - 'a is the type of the parameters of the format for formatted output
1827 functions ( printf -style functions); 'a is the type of the values read
1828 by the format for formatted input functions ( scanf -style functions).
1829 - 'b is the type of input source for formatted input functions and the
1832 type of output target for formatted output functions. For printf
1833 -style functions from module Printf , 'b is typically out_channel ; for
1834 printf -style functions from module Format , 'b is typically For‐
1835 mat.formatter ; for scanf -style functions from module Scanf , 'b is
1836 typically Scanf.Scanning.in_channel .
1837 Type argument 'b is also the type of the first argument given to user's
1839 defined printing functions for %a and %t conversions, and user's de‐
1840 fined reading functions for %r conversion.
1841 - 'c is the type of the result of the %a and %t printing functions, and
1844 also the type of the argument transmitted to the first argument of
1845 kprintf -style functions or to the kscanf -style functions.
1846 - 'd is the type of parameters for the scanf -style functions.
1849 - 'e is the type of the receiver function for the scanf -style func‐
1852 tions.
1853 - 'f is the final result type of a formatted input/output function in‐
1856 vocation: for the printf -style functions, it is typically unit ; for
1857 the scanf -style functions, it is typically the result type of the re‐
1858 ceiver function.
1859 type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam‐
1862 linternalFormatBasics.format6
1863 type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
1868 type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
1873 val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
1879 Converts a format string into a string.
1881 val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
1885 'd, 'e, 'f) format6
1886 format_of_string s returns a format string read from the string literal
1889 s . Note: format_of_string can not convert a string argument that is
1890 not a literal. If you need this functionality, use the more general
1891 Scanf.format_from_string function.
1892 val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
1896 format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
1897 f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
1900 string that behaves as the concatenation of format strings f1 and f2 :
1901 in case of formatted output, it accepts arguments from f1 , then argu‐
1902 ments from f2 ; in case of formatted input, it returns results from f1
1903 , then results from f2 . Right-associative operator, see Ocaml_opera‐
1904 tors for more information.
1905 Program termination
1910 val exit : int -> 'a
1911 Terminate the process, returning the given status code to the operating
1913 system: usually 0 to indicate no errors, and a small positive integer
1914 to indicate failure. All open output channels are flushed with
1915 flush_all . An implicit exit 0 is performed each time a program termi‐
1916 nates normally. An implicit exit 2 is performed if the program termi‐
1917 nates early because of an uncaught exception.
1918 val at_exit : (unit -> unit) -> unit
1922 Register the given function to be called at program termination time.
1924 The functions registered with at_exit will be called when the program
1925 does any of the following:
1926 -executes exit
1928 -terminates, either normally or because of an uncaught exception
1931 -executes the C function caml_shutdown . The functions are called in
1933 'last in, first out' order: the function most recently added with
1934 at_exit is called first.
1935 Standard library modules
1941 module Arg : (module Stdlib__arg)
1942 module Array : (module Stdlib__array)
1947 module ArrayLabels : (module Stdlib__arrayLabels)
1952 module Atomic : (module Stdlib__atomic)
1957 module Bigarray : (module Stdlib__bigarray)
1962 module Bool : (module Stdlib__bool)
1967 module Buffer : (module Stdlib__buffer)
1972 module Bytes : (module Stdlib__bytes)
1977 module BytesLabels : (module Stdlib__bytesLabels)
1982 module Callback : (module Stdlib__callback)
1987 module Char : (module Stdlib__char)
1992 module Complex : (module Stdlib__complex)
1997 module Digest : (module Stdlib__digest)
2002 module Either : (module Stdlib__either)
2007 module Ephemeron : (module Stdlib__ephemeron)
2012 module Filename : (module Stdlib__filename)
2017 module Float : (module Stdlib__float)
2022 module Format : (module Stdlib__format)
2027 module Fun : (module Stdlib__fun)
2032 module Gc : (module Stdlib__gc)
2037 module Genlex : (module Stdlib__genlex)
2042 module Hashtbl : (module Stdlib__hashtbl)
2047 module Int : (module Stdlib__int)
2052 module Int32 : (module Stdlib__int32)
2057 module Int64 : (module Stdlib__int64)
2062 module Lazy : (module Stdlib__lazy)
2067 module Lexing : (module Stdlib__lexing)
2072 module List : (module Stdlib__list)
2077 module ListLabels : (module Stdlib__listLabels)
2082 module Map : (module Stdlib__map)
2087 module Marshal : (module Stdlib__marshal)
2092 module MoreLabels : (module Stdlib__moreLabels)
2097 module Nativeint : (module Stdlib__nativeint)
2102 module Obj : (module Stdlib__obj)
2107 module Oo : (module Stdlib__oo)
2112 module Option : (module Stdlib__option)
2117 module Parsing : (module Stdlib__parsing)
2122 module Pervasives : (module Stdlib__pervasives)
2127 module Printexc : (module Stdlib__printexc)
2132 module Printf : (module Stdlib__printf)
2137 module Queue : (module Stdlib__queue)
2142 module Random : (module Stdlib__random)
2147 module Result : (module Stdlib__result)
2152 module Scanf : (module Stdlib__scanf)
2157 module Seq : (module Stdlib__seq)
2162 module Set : (module Stdlib__set)
2167 module Stack : (module Stdlib__stack)
2172 module StdLabels : (module Stdlib__stdLabels)
2177 module Stream : (module Stdlib__stream)
2182 module String : (module Stdlib__string)
2187 module StringLabels : (module Stdlib__stringLabels)
2192 module Sys : (module Stdlib__sys)
2197 module Uchar : (module Stdlib__uchar)
2202 module Unit : (module Stdlib__unit)
2207 module Weak : (module Stdlib__weak)
2212OCamldoc 2021-07-22 Stdlib(3)