libbatteries-ocaml-dev 2.6.0-1build1 / usr / lib / ocaml / batteries / batFormat.mli

# 1 "src/batFormat.mliv"
(*
 * BatFormat - Extended Format module
 * Copyright (C) 1996 Pierre Weis
 *               2009 David Teller, LIFO, Universite d'Orleans
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version,
 * with the special exception on linking described in file LICENSE.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *)

open BatIO

(** Pretty printing.

    This module implements a pretty-printing facility to format text
    within ``pretty-printing boxes''. The pretty-printer breaks lines
    at specified break hints, and indents lines according to the box
    structure.

    For a gentle introduction to the basics of pretty-printing using
    [Format], read
    {{:http://caml.inria.fr/resources/doc/guides/format.html}http://caml.inria.fr/resources/doc/guides/format.html}.

    You may consider this module as providing an extension to the
    [printf] facility to provide automatic line breaking. The addition of
    pretty-printing annotations to your regular [printf] formats gives you
    fancy indentation and line breaks.
    Pretty-printing annotations are described below in the documentation of
    the function {!Format.fprintf}.

    You may also use the explicit box management and printing functions
    provided by this module. This style is more basic but more verbose
    than the [fprintf] concise formats.

    For instance, the sequence
    [open_box 0; print_string "x ="; print_space ();
    print_int 1; close_box (); print_newline ()]
    that prints [x = 1] within a pretty-printing box, can be
    abbreviated as [printf "@[%s@ %i@]@." "x =" 1], or even shorter
    [printf "@[x =@ %i@]@." 1].

    Rule of thumb for casual users of this library:
    - use simple boxes (as obtained by [open_box 0]);
    - use simple break hints (as obtained by [print_cut ()] that outputs a
    simple break hint, or by [print_space ()] that outputs a space
    indicating a break hint);
    - once a box is opened, display its material with basic printing
    functions (e. g. [print_int] and [print_string]);
    - when the material for a box has been printed, call [close_box ()] to
    close the box;
    - at the end of your routine, flush the pretty-printer to display all the
    remaining material, e.g. evaluate [print_newline ()].

    The behaviour of pretty-printing commands is unspecified
    if there is no opened pretty-printing box. Each box opened via
    one of the [open_] functions below must be closed using [close_box]
    for proper formatting. Otherwise, some of the material printed in the
    boxes may not be output, or may be formatted incorrectly.

    In case of interactive use, the system closes all opened boxes and
    flushes all pending text (as with the [print_newline] function)
    after each phrase. Each phrase is therefore executed in the initial
    state of the pretty-printer.

    Warning: the material output by the following functions is delayed
    in the pretty-printer queue in order to compute the proper line
    breaking. Hence, you should not mix calls to the printing functions
    of the basic I/O system with calls to the functions of this module:
    this could result in some strange output seemingly unrelated with
    the evaluation order of printing commands.

    @author Pierre Weis (Base module)
    @author David Teller
*)

(** {6 Boxes} *)

val open_box : int -> unit;;
(** [open_box d] opens a new pretty-printing box
    with offset [d].
    This box is the general purpose pretty-printing box.
    Material in this box is displayed ``horizontal or vertical'':
    break hints inside the box may lead to a new line, if there
    is no more room on the line to print the remainder of the box,
    or if a new line may lead to a new indentation
    (demonstrating the indentation of the box).
    When a new line is printed in the box, [d] is added to the
    current indentation. *)

val close_box : unit -> unit;;
(** Closes the most recently opened pretty-printing box. *)

(** {6 Formatting functions} *)

val print_string : string -> unit;;
(** [print_string str] prints [str] in the current box. *)

val print_as : int -> string -> unit;;
(** [print_as len str] prints [str] in the
    current box. The pretty-printer formats [str] as if
    it were of length [len]. *)

val print_int : int -> unit;;
(** Prints an integer in the current box. *)

val print_float : float -> unit;;
(** Prints a floating point number in the current box. *)

val print_char : char -> unit;;
(** Prints a character in the current box. *)

val print_bool : bool -> unit;;
(** Prints a boolean in the current box. *)

(** {6 Break hints} *)

val print_space : unit -> unit;;
(** [print_space ()] is used to separate items (typically to print
    a space between two words).
    It indicates that the line may be split at this
    point. It either prints one space or splits the line.
    It is equivalent to [print_break 1 0]. *)

val print_cut : unit -> unit;;
(** [print_cut ()] is used to mark a good break position.
    It indicates that the line may be split at this
    point. It either prints nothing or splits the line.
    This allows line splitting at the current
    point, without printing spaces or adding indentation.
    It is equivalent to [print_break 0 0]. *)

val print_break : int -> int -> unit;;
(** Inserts a break hint in a pretty-printing box.
    [print_break nspaces offset] indicates that the line may
    be split (a newline character is printed) at this point,
    if the contents of the current box does not fit on the
    current line.
    If the line is split at that point, [offset] is added to
    the current indentation. If the line is not split,
    [nspaces] spaces are printed. *)

val print_flush : unit -> unit;;
(** Flushes the pretty printer: all opened boxes are closed,
    and all pending text is displayed. *)

val print_newline : unit -> unit;;
(** Equivalent to [print_flush] followed by a new line. *)

val force_newline : unit -> unit;;
(** Forces a newline in the current box. Not the normal way of
    pretty-printing, you should prefer break hints. *)

val print_if_newline : unit -> unit;;
(** Executes the next formatting command if the preceding line
    has just been split. Otherwise, ignore the next formatting
    command. *)

(** {6 Margin} *)

val set_margin : int -> unit;;
(** [set_margin d] sets the value of the right margin
    to [d] (in characters): this value is used to detect line
    overflows that leads to split lines.
    Nothing happens if [d] is smaller than 2.
    If [d] is too large, the right margin is set to the maximum
    admissible value (which is greater than [10^10]). *)

val get_margin : unit -> int;;
(** Returns the position of the right margin. *)

(** {6 Maximum indentation limit} *)

val set_max_indent : int -> unit;;
(** [set_max_indent d] sets the value of the maximum
    indentation limit to [d] (in characters):
    once this limit is reached, boxes are rejected to the left,
    if they do not fit on the current line.
    Nothing happens if [d] is smaller than 2.
    If [d] is too large, the limit is set to the maximum
    admissible value (which is greater than [10^10]). *)

val get_max_indent : unit -> int;;
(** Return the value of the maximum indentation limit (in characters). *)

(** {6 Formatting depth: maximum number of boxes allowed before ellipsis} *)

val set_max_boxes : int -> unit;;
(** [set_max_boxes max] sets the maximum number
    of boxes simultaneously opened.
    Material inside boxes nested deeper is printed as an
    ellipsis (more precisely as the text returned by
    [get_ellipsis_text ()]).
    Nothing happens if [max] is smaller than 2. *)

val get_max_boxes : unit -> int;;
(** Returns the maximum number of boxes allowed before ellipsis. *)

val over_max_boxes : unit -> bool;;
(** Tests if the maximum number of boxes allowed have already been opened. *)

(** {6 Advanced formatting} *)

val open_hbox : unit -> unit;;
(** [open_hbox ()] opens a new pretty-printing box.
    This box is ``horizontal'': the line is not split in this box
    (new lines may still occur inside boxes nested deeper). *)

val open_vbox : int -> unit;;
(** [open_vbox d] opens a new pretty-printing box
    with offset [d].
    This box is ``vertical'': every break hint inside this
    box leads to a new line.
    When a new line is printed in the box, [d] is added to the
    current indentation. *)

val open_hvbox : int -> unit;;
(** [open_hvbox d] opens a new pretty-printing box
    with offset [d].
    This box is ``horizontal-vertical'': it behaves as an
    ``horizontal'' box if it fits on a single line,
    otherwise it behaves as a ``vertical'' box.
    When a new line is printed in the box, [d] is added to the
    current indentation. *)

val open_hovbox : int -> unit;;
(** [open_hovbox d] opens a new pretty-printing box
    with offset [d].
    This box is ``horizontal or vertical'': break hints
    inside this box may lead to a new line, if there is no more room
    on the line to print the remainder of the box.
    When a new line is printed in the box, [d] is added to the
    current indentation. *)

(** {6 Tabulations} *)

val open_tbox : unit -> unit;;
(** Opens a tabulation box. *)

val close_tbox : unit -> unit;;
(** Closes the most recently opened tabulation box. *)

val print_tbreak : int -> int -> unit;;
(** Break hint in a tabulation box.
    [print_tbreak spaces offset] moves the insertion point to
    the next tabulation ([spaces] being added to this position).
    Nothing occurs if insertion point is already on a
    tabulation mark.
    If there is no next tabulation on the line, then a newline
    is printed and the insertion point moves to the first
    tabulation of the box.
    If a new line is printed, [offset] is added to the current
    indentation. *)

val set_tab : unit -> unit;;
(** Sets a tabulation mark at the current insertion point. *)

val print_tab : unit -> unit;;
(** [print_tab ()] is equivalent to [print_tbreak 0 0]. *)

(** {6 Ellipsis} *)

val set_ellipsis_text : string -> unit;;
(** Set the text of the ellipsis printed when too many boxes
    are opened (a single dot, [.], by default). *)

val get_ellipsis_text : unit -> string;;
(** Return the text of the ellipsis. *)

(** {6:tags Semantics Tags} *)

type tag = string;;

(** {i Semantics tags} (or simply {e tags}) are used to decorate printed
    entities for user's defined purposes, e.g. setting font and giving size
    indications for a display device, or marking delimitation of semantics
    entities (e.g. HTML or TeX elements or terminal escape sequences).

    By default, those tags do not influence line breaking calculation:
    the tag ``markers'' are not considered as part of the printing
    material that drives line breaking (in other words, the length of
    those strings is considered as zero for line breaking).

    Thus, tag handling is in some sense transparent to pretty-printing
    and does not interfere with usual pretty-printing. Hence, a single
    pretty printing routine can output both simple ``verbatim''
    material or richer decorated output depending on the treatment of
    tags. By default, tags are not active, hence the output is not
    decorated with tag information. Once [set_tags] is set to [true],
    the pretty printer engine honours tags and decorates the output
    accordingly.

    When a tag has been opened (or closed), it is both and successively
    ``printed'' and ``marked''. Printing a tag means calling a
    formatter specific function with the name of the tag as argument:
    that ``tag printing'' function can then print any regular material
    to the formatter (so that this material is enqueued as usual in the
    formatter queue for further line-breaking computation). Marking a
    tag means to output an arbitrary string (the ``tag marker''),
    directly into the output device of the formatter. Hence, the
    formatter specific ``tag marking'' function must return the tag
    marker string associated to its tag argument. Being flushed
    directly into the output device of the formatter, tag marker
    strings are not considered as part of the printing material that
    drives line breaking (in other words, the length of the strings
    corresponding to tag markers is considered as zero for line
    breaking). In addition, advanced users may take advantage of
    the specificity of tag markers to be precisely output when the
    pretty printer has already decided where to break the lines, and
    precisely when the queue is flushed into the output device.

    In the spirit of HTML tags, the default tag marking functions
    output tags enclosed in "<" and ">": hence, the opening marker of
    tag [t] is ["<t>"] and the closing marker ["</t>"].

    Default tag printing functions just do nothing.

    Tag marking and tag printing functions are user definable and can
    be set by calling [set_formatter_tag_functions]. *)

val open_tag : tag -> unit;;
(** [open_tag t] opens the tag named [t]; the [print_open_tag]
    function of the formatter is called with [t] as argument;
    the tag marker [mark_open_tag t] will be flushed into the output
    device of the formatter. *)
val close_tag : unit -> unit;;
(** [close_tag ()] closes the most recently opened tag [t].
    In addition, the [print_close_tag] function of the formatter is called
    with [t] as argument. The marker [mark_close_tag t] will be flushed
    into the output device of the formatter. *)

val set_tags : bool -> unit;;
(** [set_tags b] turns on or off the treatment of tags (default is off). *)
val set_print_tags : bool -> unit;;
val set_mark_tags : bool -> unit;;
(** [set_print_tags b] turns on or off the printing of tags, while
    [set_mark_tags b] turns on or off the output of tag markers. *)
val get_print_tags : unit -> bool;;
val get_mark_tags : unit -> bool;;
(** Return the current status of tags printing and tags marking. *)

(** {6 Redirecting the standard formatter output} *)

val set_formatter_output : 'a output -> unit;;
(** Sets the output of the formatter to the given argument *)

val set_formatter_output_functions :
  (string -> int -> int -> unit) -> (unit -> unit) -> unit
;;
(** [set_formatter_output_functions out flush] redirects the
    relevant pretty-printer output functions to the functions [out] and
    [flush].

    The [out] function performs the pretty-printer string output. It is called
    with a string [s], a start position [p], and a number of characters
    [n]; it is supposed to output characters [p] to [p + n - 1] of
    [s]. The [flush] function is called whenever the pretty-printer is
    flushed (via conversion [%!], pretty-printing indications [@?] or [@.],
    or using low level function [print_flush] or [print_newline]). *)

val get_formatter_output_functions :
  unit -> (string -> int -> int -> unit) * (unit -> unit)
;;
(** Return the current output functions of the pretty-printer. *)

(** {6:meaning Changing the meaning of standard formatter pretty printing} *)

(** The [Format] module is versatile enough to let you completely redefine
    the meaning of pretty printing: you may provide your own functions to define
    how to handle indentation, line breaking, and even printing of all the
    characters that have to be printed! *)

val set_all_formatter_output_functions :
  out:(string -> int -> int -> unit) ->
  flush:(unit -> unit) ->
  newline:(unit -> unit) ->
  spaces:(int -> unit) ->
  unit
;;
(** [set_all_formatter_output_functions out flush outnewline outspace]
    redirects the pretty-printer output to the functions [out] and
    [flush] as described in [set_formatter_output_functions]. In
    addition, the pretty-printer function that outputs a newline is set
    to the function [outnewline] and the function that outputs
    indentation spaces is set to the function [outspace].

    This way, you can change the meaning of indentation (which can be
    something else than just printing space characters) and the
    meaning of new lines opening (which can be connected to any other
    action needed by the application at hand). The two functions
    [outspace] and [outnewline] are normally connected to [out] and
    [flush]: respective default values for [outspace] and [outnewline]
    are [out (String.make n ' ') 0 n] and [out "\n" 0 1]. *)

val get_all_formatter_output_functions :
  unit ->
  (string -> int -> int -> unit) *
    (unit -> unit) *
    (unit -> unit) *
    (int -> unit)
;;
(** Return the current output functions of the pretty-printer,
    including line breaking and indentation functions. Useful to record the
    current setting and restore it afterwards. *)

(** {6:tags Changing the meaning of printing semantics tags} *)

type formatter_tag_functions = {
  mark_open_tag : tag -> string;
  mark_close_tag : tag -> string;
  print_open_tag : tag -> unit;
  print_close_tag : tag -> unit;
}
;;
(** The tag handling functions specific to a formatter:
    [mark] versions are the ``tag marking'' functions that associate a string
    marker to a tag in order for the pretty-printing engine to flush
    those markers as 0 length tokens in the output device of the formatter.
    [print] versions are the ``tag printing'' functions that can perform
    regular printing when a tag is closed or opened. *)

val set_formatter_tag_functions :
  formatter_tag_functions -> unit
;;

(** [set_formatter_tag_functions tag_funs] changes the meaning of
    opening and closing tags to use the functions in [tag_funs].

    When opening a tag name [t], the string [t] is passed to the
    opening tag marking function (the [mark_open_tag] field of the
    record [tag_funs]), that must return the opening tag marker for
    that name. When the next call to [close_tag ()] happens, the tag
    name [t] is sent back to the closing tag marking function (the
    [mark_close_tag] field of record [tag_funs]), that must return a
    closing tag marker for that name.

    The [print_] field of the record contains the functions that are
    called at tag opening and tag closing time, to output regular
    material in the pretty-printer queue. *)

val get_formatter_tag_functions :
  unit -> formatter_tag_functions
;;
(** Return the current tag functions of the pretty-printer. *)

(** {6 Multiple formatted output} *)

type formatter=Format.formatter;;
(** Abstract data corresponding to a pretty-printer (also called a
    formatter) and all its machinery.

    Defining new pretty-printers permits unrelated output of material in
    parallel on several output channels.
    All the parameters of a pretty-printer are local to this pretty-printer:
    margin, maximum indentation limit, maximum number of boxes
    simultaneously opened, ellipsis, and so on, are specific to
    each pretty-printer and may be fixed independently.
    Given a [Pervasives.out_channel] output channel [oc], a new formatter
    writing to that channel is simply obtained by calling
    [formatter_of_out_channel oc].
    Alternatively, the [make_formatter] function allocates a new
    formatter with explicit output and flushing functions
    (convenient to output material to strings for instance).
*)

val std_formatter : formatter;;
(** The standard formatter used by the formatting functions
    above. It is defined as [formatter_of_out_channel stdout]. *)

val err_formatter : formatter;;
(** A formatter to use with formatting functions below for
    output to standard error. It is defined as
    [formatter_of_out_channel stderr]. *)

val formatter_of_output : _ output -> formatter;;
(** [formatter_of_output out] returns a new formatter that
    writes to the corresponding output [out]. *)

val formatter_of_buffer : Buffer.t -> formatter;;
(** [formatter_of_buffer b] returns a new formatter writing to
    buffer [b]. As usual, the formatter has to be flushed at
    the end of pretty printing, using [pp_print_flush] or
    [pp_print_newline], to display all the pending material. *)

val stdbuf : Buffer.t;;
(** The string buffer in which [str_formatter] writes. *)

val str_formatter : formatter;;
(** A formatter to use with formatting functions below for
    output to the [stdbuf] string buffer.
    [str_formatter] is defined as [formatter_of_buffer stdbuf]. *)

val flush_str_formatter : unit -> string;;
(** Returns the material printed with [str_formatter], flushes
    the formatter and resets the corresponding buffer. *)

val make_formatter :
  (string -> int -> int -> unit) -> (unit -> unit) -> formatter
;;
(** [make_formatter out flush] returns a new formatter that writes according
    to the output function [out], and the flushing function [flush]. For
    instance, a formatter to the [Pervasives.out_channel] [oc] is returned by
    [make_formatter (Pervasives.output oc) (fun () -> Pervasives.flush oc)]. *)

(** {6 Basic functions to use with formatters} *)

val pp_open_hbox : formatter -> unit -> unit;;
val pp_open_vbox : formatter -> int -> unit;;
val pp_open_hvbox : formatter -> int -> unit;;
val pp_open_hovbox : formatter -> int -> unit;;
val pp_open_box : formatter -> int -> unit;;
val pp_close_box : formatter -> unit -> unit;;
val pp_open_tag : formatter -> string -> unit;;
val pp_close_tag : formatter -> unit -> unit;;
val pp_print_string : formatter -> string -> unit;;
val pp_print_as : formatter -> int -> string -> unit;;
val pp_print_int : formatter -> int -> unit;;
val pp_print_float : formatter -> float -> unit;;
val pp_print_char : formatter -> char -> unit;;
val pp_print_bool : formatter -> bool -> unit;;
val pp_print_break : formatter -> int -> int -> unit;;
val pp_print_cut : formatter -> unit -> unit;;
val pp_print_space : formatter -> unit -> unit;;
val pp_force_newline : formatter -> unit -> unit;;
val pp_print_flush : formatter -> unit -> unit;;
val pp_print_newline : formatter -> unit -> unit;;
val pp_print_if_newline : formatter -> unit -> unit;;
val pp_open_tbox : formatter -> unit -> unit;;
val pp_close_tbox : formatter -> unit -> unit;;
val pp_print_tbreak : formatter -> int -> int -> unit;;
val pp_set_tab : formatter -> unit -> unit;;
val pp_print_tab : formatter -> unit -> unit;;
val pp_set_tags : formatter -> bool -> unit;;
val pp_set_print_tags : formatter -> bool -> unit;;
val pp_set_mark_tags : formatter -> bool -> unit;;
val pp_get_print_tags : formatter -> unit -> bool;;
val pp_get_mark_tags : formatter -> unit -> bool;;
val pp_set_margin : formatter -> int -> unit;;
val pp_get_margin : formatter -> unit -> int;;
val pp_set_max_indent : formatter -> int -> unit;;
val pp_get_max_indent : formatter -> unit -> int;;
val pp_set_max_boxes : formatter -> int -> unit;;
val pp_get_max_boxes : formatter -> unit -> int;;
val pp_over_max_boxes : formatter -> unit -> bool;;
val pp_set_ellipsis_text : formatter -> string -> unit;;
val pp_get_ellipsis_text : formatter -> unit -> string;;
val pp_set_formatter_out_channel : formatter -> Pervasives.out_channel -> unit;;
val pp_set_formatter_output_functions :
  formatter -> (string -> int -> int -> unit) -> (unit -> unit) -> unit
;;
val pp_get_formatter_output_functions :
  formatter -> unit -> (string -> int -> int -> unit) * (unit -> unit)
;;
val pp_set_all_formatter_output_functions :
  formatter -> out:(string -> int -> int -> unit) -> flush:(unit -> unit) ->
  newline:(unit -> unit) -> spaces:(int -> unit) -> unit
;;
val pp_get_all_formatter_output_functions :
  formatter -> unit ->
  (string -> int -> int -> unit) * (unit -> unit) * (unit -> unit) *
    (int -> unit)
;;
val pp_set_formatter_tag_functions :
  formatter -> formatter_tag_functions -> unit
;;
val pp_get_formatter_tag_functions :
  formatter -> unit -> formatter_tag_functions
;;
(** These functions are the basic ones: usual functions
    operating on the standard formatter are defined via partial
    evaluation of these primitives. For instance,
    [print_string] is equal to [pp_print_string std_formatter]. *)

val pp_print_list:
  ?pp_sep:(formatter -> unit -> unit) ->
  (formatter -> 'a -> unit) -> (formatter -> 'a list -> unit)
(** [pp_print_list ?pp_sep pp_v ppf l] prints the list [l]. [pp_v] is
    used on the elements of [l] and each element is separated by
    a call to [pp_sep] (defaults to {!pp_print_cut}). Does nothing on
    empty lists.

    @since 4.02.0
*)

val pp_print_text : formatter -> string -> unit
(** [pp_print_text ppf s] prints [s] with spaces and newlines
    respectively printed with {!pp_print_space} and
    {!pp_force_newline}.

    @since 4.02.0
*)
  
(** {6 [printf] like functions for pretty-printing.} *)

val fprintf : formatter -> ('a, formatter, unit) format -> 'a;;

(** [fprintf ff fmt arg1 ... argN] formats the arguments [arg1] to [argN]
    according to the format string [fmt], and outputs the resulting string on
    the formatter [ff].

    The format [fmt] is a character string which contains three types of
    objects: plain characters and conversion specifications as specified in
    the [Printf] module, and pretty-printing indications specific to the
    [Format] module.

    The pretty-printing indication characters are introduced by
    a [@] character, and their meanings are:
    - [@\[]: open a pretty-printing box. The type and offset of the
     box may be optionally specified with the following syntax:
     the [<] character, followed by an optional box type indication,
     then an optional integer offset, and the closing [>] character.
     Box type is one of [h], [v], [hv], [b], or [hov],
     which stand respectively for an horizontal box, a vertical box,
     an ``horizontal-vertical'' box, or an ``horizontal or
     vertical'' box ([b] standing for an ``horizontal or
     vertical'' box demonstrating indentation and [hov] standing
     for a regular``horizontal or vertical'' box).
     For instance, [@\[<hov 2>] opens an ``horizontal or vertical''
     box with indentation 2 as obtained with [open_hovbox 2].
     For more details about boxes, see the various box opening
     functions [open_*box].
    - [@\]]: close the most recently opened pretty-printing box.
    - [@,]: output a good break as with [print_cut ()].
    - [@ ]: output a space, as with [print_space ()].
    - [@\n]: force a newline, as with [force_newline ()].
    - [@;]: output a good break as with [print_break]. The
     [nspaces] and [offset] parameters of the break may be
     optionally specified with the following syntax:
     the [<] character, followed by an integer [nspaces] value,
     then an integer [offset], and a closing [>] character.
     If no parameters are provided, the good break defaults to a
     space.
    - [@?]: flush the pretty printer as with [print_flush ()].
     This is equivalent to the conversion [%!].
    - [@.]: flush the pretty printer and output a new line, as with
     [print_newline ()].
    - [@<n>]: print the following item as if it were of length [n].
     Hence, [printf "@<0>%s" arg] is equivalent to [print_as 0 arg].
     If [@<n>] is not followed by a conversion specification,
     then the following character of the format is printed as if
     it were of length [n].
    - [@\{]: open a tag. The name of the tag may be optionally
     specified with the following syntax:
     the [<] character, followed by an optional string
     specification, and the closing [>] character. The string
     specification is any character string that does not contain the
     closing character ['>']. If omitted, the tag name defaults to the
     empty string.
     For more details about tags, see the functions [open_tag] and
     [close_tag].
    - [@\}]: close the most recently opened tag.
    - [@@]: print a plain [@] character.

    Example: [printf "@[%s@ %d@]@." "x =" 1] is equivalent to
    [open_box (); print_string "x ="; print_space ();
    print_int 1; close_box (); print_newline ()].
    It prints [x = 1] within a pretty-printing box.
*)

val printf : ('a, formatter, unit) format -> 'a;;
(** Same as [fprintf] above, but output on [std_formatter]. *)

val eprintf : ('a, formatter, unit) format -> 'a;;
(** Same as [fprintf] above, but output on [err_formatter]. *)

val sprintf : ('a, unit, string) format -> 'a;;
(** Same as [printf] above, but instead of printing on a formatter,
    returns a string containing the result of formatting the arguments.
    Note that the pretty-printer queue is flushed at the end of {e each
    call} to [sprintf].

    In case of multiple and related calls to [sprintf] to output
    material on a single string, you should consider using [fprintf]
    with the predefined formatter [str_formatter] and call
    [flush_str_formatter ()] to get the final result.

    Alternatively, you can use [Format.fprintf] with a formatter writing to a
    buffer of your own: flushing the formatter and the buffer at the end of
    pretty-printing returns the desired string. *)

val asprintf : ('a, formatter, unit, string) format4 -> 'a;;
(** Same as [printf] above, but instead of printing on a formatter, returns a
    string containing the result of formatting the arguments. The type of
    asprintf is general enough to interact nicely with [%a] conversions.
    @since 4.01.0
*)

val ifprintf : formatter -> ('a, formatter, unit) format -> 'a;;
(** Same as [fprintf] above, but does not print anything.
    Useful to ignore some material when conditionally printing.
    @since 3.10.0
*)

(** Formatted output functions with continuations. *)

val kfprintf : (formatter -> 'a) -> formatter ->
  ('b, formatter, unit, 'a) format4 -> 'b
;;
(** Same as [fprintf] above, but instead of returning immediately,
    passes the formatter to its first argument at the end of printing. *)

val ikfprintf : (formatter -> 'a) -> formatter ->
  ('b, formatter, unit, 'a) format4 -> 'b
;;
(** Same as [kfprintf] above, but does not print anything.
    Useful to ignore some material when conditionally printing.
    @since 3.12.0
*)

val ksprintf : (string -> 'a) -> ('b, unit, string, 'a) format4 -> 'b;;
(** Same as [sprintf] above, but instead of returning the string,
    passes it to the first argument. *)

(** {6 Deprecated} *)

val bprintf : Buffer.t -> ('a, formatter, unit) format -> 'a;;
(** A deprecated and error prone function. Do not use it.

    If you need to print to some buffer [b], you must first define a
    formatter writing to [b], using [let to_b = formatter_of_buffer b]; then
    use regular calls to [Format.fprintf] on formatter [to_b]. *)

val kprintf : (string -> 'a) -> ('b, unit, string, 'a) format4 -> 'b;;
(** A deprecated synonym for [ksprintf]. *)


(** {6 Basic functions to use with formatters} *)

val pp_set_formatter_output      : formatter -> _ output -> unit;;

(** {6 Deprecated}*)

val set_formatter_out_channel : _ output -> unit;;
(** Redirect the pretty-printer output to the given channel.
    (All the output functions of the standard formatter are set to the
     default output functions printing to the given channel.) *)

val formatter_of_out_channel : _ output -> formatter;;
(** [formatter_of_out_channel oc] returns a new formatter that
    writes to the corresponding channel [oc]. *)

val pp_set_formatter_out_channel : formatter -> _ output -> unit;;