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printf.mli
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(**************************************************************************)
(* *)
(* OCaml *)
(* *)
(* Xavier Leroy and Pierre Weis, projet Cristal, INRIA Rocquencourt *)
(* *)
(* Copyright 1996 Institut National de Recherche en Informatique et *)
(* en Automatique. *)
(* *)
(* All rights reserved. This file is distributed under the terms of *)
(* the GNU Lesser General Public License version 2.1, with the *)
(* special exception on linking described in the file LICENSE. *)
(* *)
(**************************************************************************)
(** Formatted output functions. *)
val fprintf : out_channel -> ('a, out_channel, unit) format -> 'a
(** [fprintf outchan format arg1 ... argN] formats the arguments
[arg1] to [argN] according to the format string [format], and
outputs the resulting string on the channel [outchan].
The format string is a character string which contains two types of
objects: plain characters, which are simply copied to the output
channel, and conversion specifications, each of which causes
conversion and printing of arguments.
Conversion specifications have the following form:
[% [flags] [width] [.precision] type]
In short, a conversion specification consists in the [%] character,
followed by optional modifiers and a type which is made of one or
two characters.
The types and their meanings are:
- [d], [i]: convert an integer argument to signed decimal.
- [u], [n], [l], [L], or [N]: convert an integer argument to
unsigned decimal. Warning: [n], [l], [L], and [N] are
used for [scanf], and should not be used for [printf].
- [x]: convert an integer argument to unsigned hexadecimal,
using lowercase letters.
- [X]: convert an integer argument to unsigned hexadecimal,
using uppercase letters.
- [o]: convert an integer argument to unsigned octal.
- [s]: insert a string argument.
- [S]: convert a string argument to OCaml syntax (double quotes, escapes).
- [c]: insert a character argument.
- [C]: convert a character argument to OCaml syntax
(single quotes, escapes).
- [f]: convert a floating-point argument to decimal notation,
in the style [dddd.ddd].
- [F]: convert a floating-point argument to OCaml syntax ([dddd.]
or [dddd.ddd] or [d.ddd e+-dd]).
- [e] or [E]: convert a floating-point argument to decimal notation,
in the style [d.ddd e+-dd] (mantissa and exponent).
- [g] or [G]: convert a floating-point argument to decimal notation,
in style [f] or [e], [E] (whichever is more compact).
- [h] or [H]: convert a floating-point argument to hexadecimal notation,
in the style [0xh.hhhh e+-dd] (hexadecimal mantissa, exponent in
decimal and denotes a power of 2).
- [B]: convert a boolean argument to the string [true] or [false]
- [b]: convert a boolean argument (deprecated; do not use in new
programs).
- [ld], [li], [lu], [lx], [lX], [lo]: convert an [int32] argument to
the format specified by the second letter (decimal, hexadecimal, etc).
- [nd], [ni], [nu], [nx], [nX], [no]: convert a [nativeint] argument to
the format specified by the second letter.
- [Ld], [Li], [Lu], [Lx], [LX], [Lo]: convert an [int64] argument to
the format specified by the second letter.
- [a]: user-defined printer. Take two arguments and apply the
first one to [outchan] (the current output channel) and to the
second argument. The first argument must therefore have type
[out_channel -> 'b -> unit] and the second ['b].
The output produced by the function is inserted in the output of
[fprintf] at the current point.
- [t]: same as [%a], but take only one argument (with type
[out_channel -> unit]) and apply it to [outchan].
- [\{ fmt %\}]: convert a format string argument to its type digest.
The argument must have the same type as the internal format string
[fmt].
- [( fmt %)]: format string substitution. Take a format string
argument and substitute it to the internal format string [fmt]
to print following arguments. The argument must have the same
type as the internal format string [fmt].
- [!]: take no argument and flush the output.
- [%]: take no argument and output one [%] character.
- [\@]: take no argument and output one [\@] character.
- [,]: take no argument and output nothing: a no-op delimiter for
conversion specifications.
The optional [flags] are:
- [-]: left-justify the output (default is right justification).
- [0]: for numerical conversions, pad with zeroes instead of spaces.
- [+]: for signed numerical conversions, prefix number with a [+]
sign if positive.
- space: for signed numerical conversions, prefix number with a
space if positive.
- [#]: request an alternate formatting style for the hexadecimal
and octal integer types ([x], [X], [o], [lx], [lX], [lo], [Lx],
[LX], [Lo]).
The optional [width] is an integer indicating the minimal
width of the result. For instance, [%6d] prints an integer,
prefixing it with spaces to fill at least 6 characters.
The optional [precision] is a dot [.] followed by an integer
indicating how many digits follow the decimal point in the [%f],
[%e], and [%E] conversions. For instance, [%.4f] prints a [float] with
4 fractional digits.
The integer in a [width] or [precision] can also be specified as
[*], in which case an extra integer argument is taken to specify
the corresponding [width] or [precision]. This integer argument
precedes immediately the argument to print.
For instance, [%.*f] prints a [float] with as many fractional
digits as the value of the argument given before the float. *)
val printf : ('a, out_channel, unit) format -> 'a
(** Same as {!Printf.fprintf}, but output on [stdout]. *)
val eprintf : ('a, out_channel, unit) format -> 'a
(** Same as {!Printf.fprintf}, but output on [stderr]. *)
val sprintf : ('a, unit, string) format -> 'a
(** Same as {!Printf.fprintf}, but instead of printing on an output channel,
return a string containing the result of formatting the arguments. *)
val bprintf : Buffer.t -> ('a, Buffer.t, unit) format -> 'a
(** Same as {!Printf.fprintf}, but instead of printing on an output channel,
append the formatted arguments to the given extensible buffer
(see module {!Buffer}). *)
val ifprintf : 'b -> ('a, 'b, 'c, unit) format4 -> 'a
(** Same as {!Printf.fprintf}, but does not print anything.
Useful to ignore some material when conditionally printing.
@since 3.10.0
*)
(** Formatted output functions with continuations. *)
val kfprintf : (out_channel -> 'd) -> out_channel ->
('a, out_channel, unit, 'd) format4 -> 'a
(** Same as [fprintf], but instead of returning immediately,
passes the out channel to its first argument at the end of printing.
@since 3.09.0
*)
val ikfprintf : ('b -> 'd) -> 'b -> ('a, 'b, 'c, 'd) format4 -> 'a
(** Same as [kfprintf] above, but does not print anything.
Useful to ignore some material when conditionally printing.
@since 4.01.0
*)
val ksprintf : (string -> 'd) -> ('a, unit, string, 'd) format4 -> 'a
(** Same as [sprintf] above, but instead of returning the string,
passes it to the first argument.
@since 3.09.0
*)
val kbprintf : (Buffer.t -> 'd) -> Buffer.t ->
('a, Buffer.t, unit, 'd) format4 -> 'a
(** Same as [bprintf], but instead of returning immediately,
passes the buffer to its first argument at the end of printing.
@since 3.10.0
*)
(** Deprecated *)
val kprintf : (string -> 'b) -> ('a, unit, string, 'b) format4 -> 'a
(** A deprecated synonym for [ksprintf]. *)