1Format(3) OCaml library Format(3)
2
6 Format - Pretty-printing.
7
9 Module Format
10
12 Module Format
13 : sig end
14 Pretty-printing.
17 This module implements a pretty-printing facility to format values
19 within Format.boxes and Format.tags combined with a set of Format.fpp .
20 The pretty-printer splits lines at specified Format.breaks , and in‐
21 dents lines according to the box structure. Similarly, Format.tags can
22 be used to decouple text presentation from its contents.
23 This pretty-printing facility is implemented as an overlay on top of
25 abstract Format.formatter which provide basic output functions. Some
26 formatters are predefined, notably:
27 - Format.std_formatter outputs to stdout
29 - Format.err_formatter outputs to stderr
32 Most functions in the Format module come in two variants: a short ver‐
34 sion that operates on the current domain's standard formatter as ob‐
35 tained using Format.get_std_formatter and the generic version prefixed
36 by pp_ that takes a formatter as its first argument. For the version
37 that operates on the current domain's standard formatter, the call to
38 Format.get_std_formatter is delayed until the last argument is re‐
39 ceived.
40 More formatters can be created with Format.formatter_of_out_channel ,
42 Format.formatter_of_buffer , Format.formatter_of_symbolic_output_buffer
43 or using Format.formatter .
44 Warning: Since Format.formatter contain mutable state, it is not
46 thread-safe to use the same formatter on multiple domains in parallel
47 without synchronization.
48 If multiple domains write to the same output channel using the prede‐
50 fined formatters (as obtained by Format.get_std_formatter or For‐
51 mat.get_err_formatter ), the output from the domains will be inter‐
52 leaved with each other at points where the formatters are flushed, such
53 as with Format.print_flush . This synchronization is not performed by
54 formatters obtained from Format.formatter_of_out_channel (on the stan‐
55 dard out channels or others).
56 Introduction
64 You may consider this module as providing an extension to the printf
65 facility to provide automatic line splitting. The addition of
66 pretty-printing annotations to your regular printf format strings gives
67 you fancy indentation and line breaks. Pretty-printing annotations are
68 described below in the documentation of the function Format.fprintf .
69 You may also use the explicit pretty-printing box management and print‐
71 ing functions provided by this module. This style is more basic but
72 more verbose than the concise fprintf format strings.
73 For instance, the sequence open_box 0; print_string "x ="; print_space
75 ();
76 print_int 1; close_box (); print_newline () that prints x = 1
77 within a pretty-printing box, can be abbreviated as printf "@[%s@
78 %i@]@." "x =" 1 , or even shorter printf "@[x =@ %i@]@." 1 .
79 Rule of thumb for casual users of this library:
81 -use simple pretty-printing boxes (as obtained by open_box 0 );
83 -use simple break hints as obtained by print_cut () that outputs a sim‐
85 ple break hint, or by print_space () that outputs a space indicating a
86 break hint;
87 -once a pretty-printing box is open, display its material with basic
89 printing functions (e. g. print_int and print_string );
90 -when the material for a pretty-printing box has been printed, call
92 close_box () to close the box;
93 -at the end of pretty-printing, flush the pretty-printer to display all
95 the remaining material, e.g. evaluate print_newline () .
96 The behavior of pretty-printing commands is unspecified if there is no
98 open pretty-printing box. Each box opened by one of the open_ functions
99 below must be closed using close_box for proper formatting. Otherwise,
100 some of the material printed in the boxes may not be output, or may be
101 formatted incorrectly.
102 In case of interactive use, each phrase is executed in the initial
104 state of the standard pretty-printer: after each phrase execution, the
105 interactive system closes all open pretty-printing boxes, flushes all
106 pending text, and resets the standard pretty-printer.
107 Warning: mixing calls to pretty-printing functions of this module with
109 calls to Stdlib low level output functions is error prone.
110 The pretty-printing functions output material that is delayed in the
112 pretty-printer queue and stacks in order to compute proper line split‐
113 ting. In contrast, basic I/O output functions write directly in their
114 output device. As a consequence, the output of a basic I/O function may
115 appear before the output of a pretty-printing function that has been
116 called before. For instance,
117 Stdlib.print_string "<";
118 Format.print_string "PRETTY";
119 Stdlib.print_string ">";
120 Format.print_string "TEXT";
121 leads to output <>PRETTYTEXT .
122 Formatters
124 type formatter
125 Abstract data corresponding to a pretty-printer (also called a format‐
128 ter) and all its machinery. See also Format.formatter .
129 Pretty-printing boxes
134 The pretty-printing engine uses the concepts of pretty-printing box and
135 break hint to drive indentation and line splitting behavior of the
136 pretty-printer.
137 Each different pretty-printing box kind introduces a specific line
139 splitting policy:
140 -within an horizontal box, break hints never split the line (but the
143 line may be split in a box nested deeper),
144 -within a vertical box, break hints always split the line,
146 -within an horizontal/vertical box, if the box fits on the current line
148 then break hints never split the line, otherwise break hint always
149 split the line,
150 -within a compacting box, a break hint never splits the line, unless
152 there is no more room on the current line.
153 Note that line splitting policy is box specific: the policy of a box
155 does not rule the policy of inner boxes. For instance, if a vertical
156 box is nested in an horizontal box, all break hints within the vertical
157 box will split the line.
158 Moreover, opening a box after the Format.maxindent splits the line
160 whether or not the box would end up fitting on the line.
161 val pp_open_box : formatter -> int -> unit
163 val open_box : int -> unit
168 pp_open_box ppf d opens a new compacting pretty-printing box with off‐
171 set d in the formatter ppf .
172 Within this box, the pretty-printer prints as much as possible material
174 on every line.
175 A break hint splits the line if there is no more room on the line to
177 print the remainder of the box.
178 Within this box, the pretty-printer emphasizes the box structure: if a
180 structural box does not fit fully on a simple line, a break hint also
181 splits the line if the splitting ``moves to the left'' (i.e. the new
182 line gets an indentation smaller than the one of the current line).
183 This box is the general purpose pretty-printing box.
185 If the pretty-printer splits the line in the box, offset d is added to
187 the current indentation.
188 val pp_close_box : formatter -> unit -> unit
192 val close_box : unit -> unit
197 Closes the most recently open pretty-printing box.
199 val pp_open_hbox : formatter -> unit -> unit
203 val open_hbox : unit -> unit
208 pp_open_hbox ppf () opens a new 'horizontal' pretty-printing box.
211 This box prints material on a single line.
213 Break hints in a horizontal box never split the line. (Line splitting
215 may still occur inside boxes nested deeper).
216 val pp_open_vbox : formatter -> int -> unit
220 val open_vbox : int -> unit
225 pp_open_vbox ppf d opens a new 'vertical' pretty-printing box with off‐
228 set d .
229 This box prints material on as many lines as break hints in the box.
231 Every break hint in a vertical box splits the line.
233 If the pretty-printer splits the line in the box, d is added to the
235 current indentation.
236 val pp_open_hvbox : formatter -> int -> unit
240 val open_hvbox : int -> unit
245 pp_open_hvbox ppf d opens a new 'horizontal/vertical' pretty-printing
248 box with offset d .
249 This box behaves as an horizontal box if it fits on a single line, oth‐
251 erwise it behaves as a vertical box.
252 If the pretty-printer splits the line in the box, d is added to the
254 current indentation.
255 val pp_open_hovbox : formatter -> int -> unit
259 val open_hovbox : int -> unit
264 pp_open_hovbox ppf d opens a new 'horizontal-or-vertical' pretty-print‐
267 ing box with offset d .
268 This box prints material as much as possible on every line.
270 A break hint splits the line if there is no more room on the line to
272 print the remainder of the box.
273 If the pretty-printer splits the line in the box, d is added to the
275 current indentation.
276 Formatting functions
281 val pp_print_string : formatter -> string -> unit
282 val print_string : string -> unit
287 pp_print_string ppf s prints s in the current pretty-printing box.
290 val pp_print_bytes : formatter -> bytes -> unit
294 val print_bytes : bytes -> unit
299 pp_print_bytes ppf b prints b in the current pretty-printing box.
302 Since 4.13.0
305 val pp_print_as : formatter -> int -> string -> unit
309 val print_as : int -> string -> unit
314 pp_print_as ppf len s prints s in the current pretty-printing box. The
317 pretty-printer formats s as if it were of length len .
318 val pp_print_int : formatter -> int -> unit
322 val print_int : int -> unit
327 Print an integer in the current pretty-printing box.
329 val pp_print_float : formatter -> float -> unit
333 val print_float : float -> unit
338 Print a floating point number in the current pretty-printing box.
340 val pp_print_char : formatter -> char -> unit
344 val print_char : char -> unit
349 Print a character in the current pretty-printing box.
351 val pp_print_bool : formatter -> bool -> unit
355 val print_bool : bool -> unit
360 Print a boolean in the current pretty-printing box.
362 Break hints
367 A 'break hint' tells the pretty-printer to output some space or split
368 the line whichever way is more appropriate to the current pretty-print‐
369 ing box splitting rules.
370 Break hints are used to separate printing items and are mandatory to
372 let the pretty-printer correctly split lines and indent items.
373 Simple break hints are:
375 -the 'space': output a space or split the line if appropriate,
377 -the 'cut': split the line if appropriate.
379 Note: the notions of space and line splitting are abstract for the
381 pretty-printing engine, since those notions can be completely redefined
382 by the programmer. However, in the pretty-printer default setting,
383 ``output a space'' simply means printing a space character (ASCII code
384 32) and ``split the line'' means printing a newline character (ASCII
385 code 10).
386 val pp_print_space : formatter -> unit -> unit
388 val print_space : unit -> unit
393 pp_print_space ppf () emits a 'space' break hint: the pretty-printer
396 may split the line at this point, otherwise it prints one space.
397 pp_print_space ppf () is equivalent to pp_print_break ppf 1 0 .
400 val pp_print_cut : formatter -> unit -> unit
404 val print_cut : unit -> unit
409 pp_print_cut ppf () emits a 'cut' break hint: the pretty-printer may
412 split the line at this point, otherwise it prints nothing.
413 pp_print_cut ppf () is equivalent to pp_print_break ppf 0 0 .
416 val pp_print_break : formatter -> int -> int -> unit
420 val print_break : int -> int -> unit
425 pp_print_break ppf nspaces offset emits a 'full' break hint: the
428 pretty-printer may split the line at this point, otherwise it prints
429 nspaces spaces.
430 If the pretty-printer splits the line, offset is added to the current
432 indentation.
433 val pp_print_custom_break : formatter -> fits:string * int * string ->
437 breaks:string * int * string -> unit
438 pp_print_custom_break ppf ~fits:(s1, n, s2) ~breaks:(s3, m, s4) emits a
441 custom break hint: the pretty-printer may split the line at this point.
442 If it does not split the line, then the s1 is emitted, then n spaces,
444 then s2 .
445 If it splits the line, then it emits the s3 string, then an indent (ac‐
447 cording to the box rules), then an offset of m spaces, then the s4
448 string.
449 While n and m are handled by formatter_out_functions.out_indent , the
451 strings will be handled by formatter_out_functions.out_string . This
452 allows for a custom formatter that handles indentation distinctly, for
453 example, outputs <br/> tags or entities.
454 The custom break is useful if you want to change which visible
456 (non-whitespace) characters are printed in case of break or no break.
457 For example, when printing a list [a; b; c] , you might want to add a
458 trailing semicolon when it is printed vertically:
459 [
462 a;
463 b;
464 c;
465 ]
466 You can do this as follows:
469 printf "@[<v 0>[@;<0 2>@[<v 0>a;@,b;@,c@]%t]@]@\n"
470 (pp_print_custom_break ~fits:("", 0, "") ~breaks:(";", 0, ""))
471 Since 4.08.0
475 val pp_force_newline : formatter -> unit -> unit
479 val force_newline : unit -> unit
484 Force a new line in the current pretty-printing box.
486 The pretty-printer must split the line at this point,
488 Not the normal way of pretty-printing, since imperative line splitting
490 may interfere with current line counters and box size calculation. Us‐
491 ing break hints within an enclosing vertical box is a better alterna‐
492 tive.
493 val pp_print_if_newline : formatter -> unit -> unit
497 val print_if_newline : unit -> unit
502 Execute the next formatting command if the preceding line has just been
504 split. Otherwise, ignore the next formatting command.
505 Pretty-printing termination
510 val pp_print_flush : formatter -> unit -> unit
511 val print_flush : unit -> unit
516 End of pretty-printing: resets the pretty-printer to initial state.
518 All open pretty-printing boxes are closed, all pending text is printed.
520 In addition, the pretty-printer low level output device is flushed to
521 ensure that all pending text is really displayed.
522 Note: never use print_flush in the normal course of a pretty-printing
524 routine, since the pretty-printer uses a complex buffering machinery to
525 properly indent the output; manually flushing those buffers at random
526 would conflict with the pretty-printer strategy and result to poor ren‐
527 dering.
528 Only consider using print_flush when displaying all pending material is
530 mandatory (for instance in case of interactive use when you want the
531 user to read some text) and when resetting the pretty-printer state
532 will not disturb further pretty-printing.
533 Warning: If the output device of the pretty-printer is an output chan‐
535 nel, repeated calls to print_flush means repeated calls to flush to
536 flush the out channel; these explicit flush calls could foil the
537 buffering strategy of output channels and could dramatically impact ef‐
538 ficiency.
539 val pp_print_newline : formatter -> unit -> unit
543 val print_newline : unit -> unit
548 End of pretty-printing: resets the pretty-printer to initial state.
550 All open pretty-printing boxes are closed, all pending text is printed.
552 Equivalent to Format.print_flush followed by a new line. See corre‐
554 sponding words of caution for Format.print_flush .
555 Note: this is not the normal way to output a new line; the preferred
557 method is using break hints within a vertical pretty-printing box.
558 Margin
563 val pp_set_margin : formatter -> int -> unit
564 val set_margin : int -> unit
569 pp_set_margin ppf d sets the right margin to d (in characters): the
572 pretty-printer splits lines that overflow the right margin according to
573 the break hints given. Setting the margin to d means that the format‐
574 ting engine aims at printing at most d-1 characters per line. Nothing
575 happens if d is smaller than 2. If d is too large, the right margin is
576 set to the maximum admissible value (which is greater than 10 ^ 9 ).
577 If d is less than the current maximum indentation limit, the maximum
578 indentation limit is decreased while trying to preserve a minimal ratio
579 max_indent/margin>=50% and if possible the current difference margin -
580 max_indent .
581 See also Format.pp_set_geometry .
583 val pp_get_margin : formatter -> unit -> int
587 val get_margin : unit -> int
592 Returns the position of the right margin.
594 Maximum indentation limit
599 val pp_set_max_indent : formatter -> int -> unit
600 val set_max_indent : int -> unit
605 pp_set_max_indent ppf d sets the maximum indentation limit of lines to
608 d (in characters): once this limit is reached, new pretty-printing
609 boxes are rejected to the left, unless the enclosing box fully fits on
610 the current line. As an illustration,
611 set_margin 10; set_max_indent 5; printf "@[123456@[7@]89A@]@."
612 yields
613 123456
614 789A
615 because the nested box "@[7@]" is opened after the maximum indentation
617 limit ( 7>5 ) and its parent box does not fit on the current line. Ei‐
618 ther decreasing the length of the parent box to make it fit on a line:
619 printf "@[123456@[7@]89@]@."
620 or opening an intermediary box before the maximum indentation limit
621 which fits on the current line
622 printf "@[123@[456@[7@]89@]A@]@."
623 avoids the rejection to the left of the inner boxes and print respec‐
624 tively "123456789" and "123456789A" . Note also that vertical boxes
625 never fit on a line whereas horizontal boxes always fully fit on the
626 current line. Opening a box may split a line whereas the contents may
627 have fit. If this behavior is problematic, it can be curtailed by set‐
628 ting the maximum indentation limit to margin - 1 . Note that setting
629 the maximum indentation limit to margin is invalid.
630 Nothing happens if d is smaller than 2.
632 If d is too large, the limit is set to the maximum admissible value
634 (which is greater than 10 ^ 9 ).
635 If d is greater or equal than the current margin, it is ignored, and
637 the current maximum indentation limit is kept.
638 See also Format.pp_set_geometry .
640 val pp_get_max_indent : formatter -> unit -> int
644 val get_max_indent : unit -> int
649 Return the maximum indentation limit (in characters).
651 Geometry
656 Geometric functions can be used to manipulate simultaneously the cou‐
657 pled variables, margin and maxixum indentation limit.
658 type geometry = {
660 max_indent : int ;
661 margin : int ;
662 }
663 Since 4.08
666 val check_geometry : geometry -> bool
670 Check if the formatter geometry is valid: 1 < max_indent < margin
672 Since 4.08
676 val pp_set_geometry : formatter -> max_indent:int -> margin:int -> unit
680 val set_geometry : max_indent:int -> margin:int -> unit
685 val pp_safe_set_geometry : formatter -> max_indent:int -> margin:int ->
690 unit
691 val safe_set_geometry : max_indent:int -> margin:int -> unit
696 pp_set_geometry ppf ~max_indent ~margin sets both the margin and maxi‐
699 mum indentation limit for ppf .
700 When 1 < max_indent < margin , pp_set_geometry ppf ~max_indent ~margin
702 is equivalent to pp_set_margin ppf margin; pp_set_max_indent ppf
703 max_indent ; and avoids the subtly incorrect pp_set_max_indent ppf
704 max_indent; pp_set_margin ppf margin ;
705 Outside of this domain, pp_set_geometry raises an invalid argument ex‐
707 ception whereas pp_safe_set_geometry does nothing.
708 Since 4.08.0
711 val pp_update_geometry : formatter -> (geometry -> geometry) -> unit
715 pp_update_geometry ppf (fun geo -> { geo with ... }) lets you update a
718 formatter's geometry in a way that is robust to extension of the geome‐
719 try record with new fields.
720 Raises an invalid argument exception if the returned geometry does not
722 satisfy Format.check_geometry .
723 Since 4.11.0
726 val update_geometry : (geometry -> geometry) -> unit
730 val pp_get_geometry : formatter -> unit -> geometry
735 val get_geometry : unit -> geometry
740 Return the current geometry of the formatter
742 Since 4.08.0
745 Maximum formatting depth
750 The maximum formatting depth is the maximum number of pretty-printing
751 boxes simultaneously open.
752 Material inside boxes nested deeper is printed as an ellipsis (more
754 precisely as the text returned by Format.get_ellipsis_text () ).
755 val pp_set_max_boxes : formatter -> int -> unit
757 val set_max_boxes : int -> unit
762 pp_set_max_boxes ppf max sets the maximum number of pretty-printing
765 boxes simultaneously open.
766 Material inside boxes nested deeper is printed as an ellipsis (more
768 precisely as the text returned by Format.get_ellipsis_text () ).
769 Nothing happens if max is smaller than 2.
771 val pp_get_max_boxes : formatter -> unit -> int
775 val get_max_boxes : unit -> int
780 Returns the maximum number of pretty-printing boxes allowed before el‐
782 lipsis.
783 val pp_over_max_boxes : formatter -> unit -> bool
787 val over_max_boxes : unit -> bool
792 Tests if the maximum number of pretty-printing boxes allowed have al‐
794 ready been opened.
795 Tabulation boxes
800 A tabulation box prints material on lines divided into cells of fixed
801 length. A tabulation box provides a simple way to display vertical col‐
802 umns of left adjusted text.
803 This box features command set_tab to define cell boundaries, and com‐
805 mand print_tab to move from cell to cell and split the line when there
806 is no more cells to print on the line.
807 Note: printing within tabulation box is line directed, so arbitrary
809 line splitting inside a tabulation box leads to poor rendering. Yet,
810 controlled use of tabulation boxes allows simple printing of columns
811 within module Format .
812 val pp_open_tbox : formatter -> unit -> unit
814 val open_tbox : unit -> unit
819 open_tbox () opens a new tabulation box.
822 This box prints lines separated into cells of fixed width.
824 Inside a tabulation box, special tabulation markers defines points of
826 interest on the line (for instance to delimit cell boundaries). Func‐
827 tion Format.set_tab sets a tabulation marker at insertion point.
828 A tabulation box features specific tabulation breaks to move to next
830 tabulation marker or split the line. Function Format.print_tbreak
831 prints a tabulation break.
832 val pp_close_tbox : formatter -> unit -> unit
836 val close_tbox : unit -> unit
841 Closes the most recently opened tabulation box.
843 val pp_set_tab : formatter -> unit -> unit
847 val set_tab : unit -> unit
852 Sets a tabulation marker at current insertion point.
854 val pp_print_tab : formatter -> unit -> unit
858 val print_tab : unit -> unit
863 print_tab () emits a 'next' tabulation break hint: if not already set
866 on a tabulation marker, the insertion point moves to the first tabula‐
867 tion marker on the right, or the pretty-printer splits the line and in‐
868 sertion point moves to the leftmost tabulation marker.
869 It is equivalent to print_tbreak 0 0 .
871 val pp_print_tbreak : formatter -> int -> int -> unit
875 val print_tbreak : int -> int -> unit
880 print_tbreak nspaces offset emits a 'full' tabulation break hint.
883 If not already set on a tabulation marker, the insertion point moves to
885 the first tabulation marker on the right and the pretty-printer prints
886 nspaces spaces.
887 If there is no next tabulation marker on the right, the pretty-printer
889 splits the line at this point, then insertion point moves to the left‐
890 most tabulation marker of the box.
891 If the pretty-printer splits the line, offset is added to the current
893 indentation.
894 Ellipsis
899 val pp_set_ellipsis_text : formatter -> string -> unit
900 val set_ellipsis_text : string -> unit
905 Set the text of the ellipsis printed when too many pretty-printing
907 boxes are open (a single dot, . , by default).
908 val pp_get_ellipsis_text : formatter -> unit -> string
912 val get_ellipsis_text : unit -> string
917 Return the text of the ellipsis.
919 Semantic tags
924 type stag = ..
925 Semantic tags (or simply tags) are user's defined annotations to asso‐
928 ciate user's specific operations to printed entities.
929 Common usage of semantic tags is text decoration to get specific font
931 or text size rendering for a display device, or marking delimitation of
932 entities (e.g. HTML or TeX elements or terminal escape sequences).
933 More sophisticated usage of semantic tags could handle dynamic modifi‐
934 cation of the pretty-printer behavior to properly print the material
935 within some specific tags. For instance, we can define an RGB tag like
936 so:
937 type stag += RGB of {r:int;g:int;b:int}
938 In order to properly delimit printed entities, a semantic tag must be
941 opened before and closed after the entity. Semantic tags must be prop‐
942 erly nested like parentheses using Format.pp_open_stag and For‐
943 mat.pp_close_stag .
944 Tag specific operations occur any time a tag is opened or closed, At
946 each occurrence, two kinds of operations are performed tag-marking and
947 tag-printing:
948 -The tag-marking operation is the simpler tag specific operation: it
950 simply writes a tag specific string into the output device of the for‐
951 matter. Tag-marking does not interfere with line-splitting computation.
952 -The tag-printing operation is the more involved tag specific opera‐
954 tion: it can print arbitrary material to the formatter. Tag-printing is
955 tightly linked to the current pretty-printer operations.
956 Roughly speaking, tag-marking is commonly used to get a better render‐
958 ing of texts in the rendering device, while tag-printing allows fine
959 tuning of printing routines to print the same entity differently ac‐
960 cording to the semantic tags (i.e. print additional material or even
961 omit parts of the output).
962 More precisely: when a semantic tag is opened or closed then both and
964 successive 'tag-printing' and 'tag-marking' operations occur:
965 -Tag-printing a semantic tag means calling the formatter specific func‐
967 tion print_open_stag (resp. print_close_stag ) with the name of the
968 tag as argument: that tag-printing function can then print any regular
969 material to the formatter (so that this material is enqueued as usual
970 in the formatter queue for further line splitting computation).
971 -Tag-marking a semantic tag means calling the formatter specific func‐
973 tion mark_open_stag (resp. mark_close_stag ) with the name of the tag
974 as argument: that tag-marking function can then return the 'tag-opening
975 marker' (resp. `tag-closing marker') for direct output into the output
976 device of the formatter.
977 Being written directly into the output device of the formatter, seman‐
979 tic tag marker strings are not considered as part of the printing mate‐
980 rial that drives line splitting (in other words, the length of the
981 strings corresponding to tag markers is considered as zero for line
982 splitting).
983 Thus, semantic tag handling is in some sense transparent to
985 pretty-printing and does not interfere with usual indentation. Hence, a
986 single pretty-printing routine can output both simple 'verbatim' mate‐
987 rial or richer decorated output depending on the treatment of tags. By
988 default, tags are not active, hence the output is not decorated with
989 tag information. Once set_tags is set to true , the pretty-printer en‐
990 gine honors tags and decorates the output accordingly.
991 Default tag-marking functions behave the HTML way: Format.tag are en‐
993 closed in "<" and ">" while other tags are ignored; hence, opening
994 marker for tag string "t" is "<t>" and closing marker is "</t>" .
995 Default tag-printing functions just do nothing.
997 Tag-marking and tag-printing functions are user definable and can be
999 set by calling Format.set_formatter_stag_functions .
1000 Semantic tag operations may be set on or off with Format.set_tags .
1002 Tag-marking operations may be set on or off with Format.set_mark_tags .
1003 Tag-printing operations may be set on or off with Format.set_print_tags
1004 .
1005 Since 4.08.0
1008 type tag = string
1011 type stag +=
1016 | String_tag of tag (* String_tag s is a string tag s . String tags
1017 can be inserted either by explicitly using the constructor String_tag
1018 or by using the dedicated format syntax "@{<s> ... @}" .
1019 Since 4.08.0
1022 *)
1023 val pp_open_stag : formatter -> stag -> unit
1029 val open_stag : stag -> unit
1034 pp_open_stag ppf t opens the semantic tag named t .
1037 The print_open_stag tag-printing function of the formatter is called
1039 with t as argument; then the opening tag marker for t , as given by
1040 mark_open_stag t , is written into the output device of the formatter.
1041 Since 4.08.0
1044 val pp_close_stag : formatter -> unit -> unit
1048 val close_stag : unit -> unit
1053 pp_close_stag ppf () closes the most recently opened semantic tag t .
1056 The closing tag marker, as given by mark_close_stag t , is written into
1058 the output device of the formatter; then the print_close_stag
1059 tag-printing function of the formatter is called with t as argument.
1060 Since 4.08.0
1063 val pp_set_tags : formatter -> bool -> unit
1067 val set_tags : bool -> unit
1072 pp_set_tags ppf b turns on or off the treatment of semantic tags (de‐
1075 fault is off).
1076 val pp_set_print_tags : formatter -> bool -> unit
1080 val set_print_tags : bool -> unit
1085 pp_set_print_tags ppf b turns on or off the tag-printing operations.
1088 val pp_set_mark_tags : formatter -> bool -> unit
1092 val set_mark_tags : bool -> unit
1097 pp_set_mark_tags ppf b turns on or off the tag-marking operations.
1100 val pp_get_print_tags : formatter -> unit -> bool
1104 val get_print_tags : unit -> bool
1109 Return the current status of tag-printing operations.
1111 val pp_get_mark_tags : formatter -> unit -> bool
1115 val get_mark_tags : unit -> bool
1120 Return the current status of tag-marking operations.
1122 val pp_set_formatter_out_channel : formatter -> out_channel -> unit
1126 Redirecting the standard formatter output
1129 val set_formatter_out_channel : out_channel -> unit
1130 Redirect the standard pretty-printer output to the given channel. (All
1132 the output functions of the standard formatter are set to the default
1133 output functions printing to the given channel.)
1134 set_formatter_out_channel is equivalent to Format.pp_set_format‐
1137 ter_out_channel std_formatter .
1138 val pp_set_formatter_output_functions : formatter -> (string -> int ->
1142 int -> unit) -> (unit -> unit) -> unit
1143 val set_formatter_output_functions : (string -> int -> int -> unit) ->
1148 (unit -> unit) -> unit
1149 pp_set_formatter_output_functions ppf out flush redirects the standard
1152 pretty-printer output functions to the functions out and flush .
1153 The out function performs all the pretty-printer string output. It is
1155 called with a string s , a start position p , and a number of charac‐
1156 ters n ; it is supposed to output characters p to p + n - 1 of s .
1157 The flush function is called whenever the pretty-printer is flushed
1159 (via conversion %! , or pretty-printing indications @? or @. , or
1160 using low level functions print_flush or print_newline ).
1161 val pp_get_formatter_output_functions : formatter -> unit -> (string ->
1165 int -> int -> unit) * (unit -> unit)
1166 val get_formatter_output_functions : unit -> (string -> int -> int ->
1171 unit) * (unit -> unit)
1172 Return the current output functions of the standard pretty-printer.
1174 Redefining formatter output
1179 The Format module is versatile enough to let you completely redefine
1180 the meaning of pretty-printing output: you may provide your own func‐
1181 tions to define how to handle indentation, line splitting, and even
1182 printing of all the characters that have to be printed!
1183 Redefining output functions
1185 type formatter_out_functions = {
1186 out_string : string -> int -> int -> unit ;
1187 out_flush : unit -> unit ;
1188 out_newline : unit -> unit ;
1189 out_spaces : int -> unit ;
1190 out_indent : int -> unit ; (* .B "Since" 4.06.0
1191 *)
1192 }
1193 The set of output functions specific to a formatter:
1196 -the out_string function performs all the pretty-printer string output.
1198 It is called with a string s , a start position p , and a number of
1199 characters n ; it is supposed to output characters p to p + n - 1 of s
1200 .
1201 -the out_flush function flushes the pretty-printer output device.
1203 - out_newline is called to open a new line when the pretty-printer
1205 splits the line.
1206 -the out_spaces function outputs spaces when a break hint leads to spa‐
1208 ces instead of a line split. It is called with the number of spaces to
1209 output.
1210 -the out_indent function performs new line indentation when the
1212 pretty-printer splits the line. It is called with the indentation value
1213 of the new line.
1214 By default:
1216 -fields out_string and out_flush are output device specific; (e.g.
1218 output_string and flush for a out_channel device, or Buffer.add_sub‐
1219 string and ignore for a Buffer.t output device),
1220 -field out_newline is equivalent to out_string "\n" 0 1 ;
1222 -fields out_spaces and out_indent are equivalent to out_string
1224 (String.make n ' ') 0 n .
1225 Since 4.01.0
1229 val pp_set_formatter_out_functions : formatter -> formatter_out_func‐
1233 tions -> unit
1234 val set_formatter_out_functions : formatter_out_functions -> unit
1239 pp_set_formatter_out_functions ppf out_funs Set all the pretty-printer
1242 output functions of ppf to those of argument out_funs ,
1243 This way, you can change the meaning of indentation (which can be some‐
1245 thing else than just printing space characters) and the meaning of new
1246 lines opening (which can be connected to any other action needed by the
1247 application at hand).
1248 Reasonable defaults for functions out_spaces and out_newline are re‐
1250 spectively out_funs.out_string (String.make n ' ') 0 n and
1251 out_funs.out_string "\n" 0 1 .
1252 Since 4.01.0
1255 val pp_get_formatter_out_functions : formatter -> unit -> format‐
1259 ter_out_functions
1260 val get_formatter_out_functions : unit -> formatter_out_functions
1265 Return the current output functions of the pretty-printer, including
1267 line splitting and indentation functions. Useful to record the current
1268 setting and restore it afterwards.
1269 Since 4.01.0
1272 Redefining semantic tag operations
1277 type formatter_stag_functions = {
1278 mark_open_stag : stag -> string ;
1279 mark_close_stag : stag -> string ;
1280 print_open_stag : stag -> unit ;
1281 print_close_stag : stag -> unit ;
1282 }
1283 The semantic tag handling functions specific to a formatter: mark ver‐
1286 sions are the 'tag-marking' functions that associate a string marker to
1287 a tag in order for the pretty-printing engine to write those markers as
1288 0 length tokens in the output device of the formatter. print versions
1289 are the 'tag-printing' functions that can perform regular printing when
1290 a tag is closed or opened.
1291 Since 4.08.0
1294 val pp_set_formatter_stag_functions : formatter -> formatter_stag_func‐
1298 tions -> unit
1299 val set_formatter_stag_functions : formatter_stag_functions -> unit
1304 pp_set_formatter_stag_functions ppf tag_funs changes the meaning of
1307 opening and closing semantic tag operations to use the functions in
1308 tag_funs when printing on ppf .
1309 When opening a semantic tag with name t , the string t is passed to the
1311 opening tag-marking function (the mark_open_stag field of the record
1312 tag_funs ), that must return the opening tag marker for that name. When
1313 the next call to close_stag () happens, the semantic tag name t is sent
1314 back to the closing tag-marking function (the mark_close_stag field of
1315 record tag_funs ), that must return a closing tag marker for that name.
1316 The print_ field of the record contains the tag-printing functions that
1318 are called at tag opening and tag closing time, to output regular mate‐
1319 rial in the pretty-printer queue.
1320 Since 4.08.0
1323 val pp_get_formatter_stag_functions : formatter -> unit -> format‐
1327 ter_stag_functions
1328 val get_formatter_stag_functions : unit -> formatter_stag_functions
1333 Return the current semantic tag operation functions of the standard
1335 pretty-printer.
1336 Since 4.08.0
1339 Defining formatters
1344 Defining new formatters permits unrelated output of material in paral‐
1345 lel on several output devices. All the parameters of a formatter are
1346 local to the formatter: right margin, maximum indentation limit, maxi‐
1347 mum number of pretty-printing boxes simultaneously open, ellipsis, and
1348 so on, are specific to each formatter and may be fixed independently.
1349 For instance, given a Buffer.t buffer b , Format.formatter_of_buffer b
1351 returns a new formatter using buffer b as its output device. Simi‐
1352 larly, given a out_channel output channel oc , Format.format‐
1353 ter_of_out_channel oc returns a new formatter using channel oc as its
1354 output device.
1355 Alternatively, given out_funs , a complete set of output functions for
1357 a formatter, then Format.formatter_of_out_functions out_funs computes a
1358 new formatter using those functions for output.
1359 val formatter_of_out_channel : out_channel -> formatter
1361 formatter_of_out_channel oc returns a new formatter writing to the cor‐
1364 responding output channel oc .
1365 val synchronized_formatter_of_out_channel : out_channel -> formatter
1369 Domain.DLS.key
1370 synchronized_formatter_of_out_channel oc returns the key to the do‐
1373 main-local state that holds the domain-local formatter for writing to
1374 the corresponding output channel oc .
1375 When the formatter is used with multiple domains, the output from the
1377 domains will be interleaved with each other at points where the format‐
1378 ter is flushed, such as with Format.print_flush .
1379 Alert unstable.
1382 val std_formatter : formatter
1386 The initial domain's standard formatter to write to standard output.
1388 It is defined as Format.formatter_of_out_channel stdout .
1390 val get_std_formatter : unit -> formatter
1394 get_std_formatter () returns the current domain's standard formatter
1397 used to write to standard output.
1398 Since 5.0
1401 val err_formatter : formatter
1405 The initial domain's formatter to write to standard error.
1407 It is defined as Format.formatter_of_out_channel stderr .
1409 val get_err_formatter : unit -> formatter
1413 get_err_formatter () returns the current domain's formatter used to
1416 write to standard error.
1417 Since 5.0
1420 val formatter_of_buffer : Buffer.t -> formatter
1424 formatter_of_buffer b returns a new formatter writing to buffer b . At
1427 the end of pretty-printing, the formatter must be flushed using For‐
1428 mat.pp_print_flush or Format.pp_print_newline , to print all the pend‐
1429 ing material into the buffer.
1430 val stdbuf : Buffer.t
1434 The initial domain's string buffer in which str_formatter writes.
1436 val get_stdbuf : unit -> Buffer.t
1440 get_stdbuf () returns the current domain's string buffer in which the
1443 current domain's string formatter writes.
1444 Since 5.0
1447 val str_formatter : formatter
1451 The initial domain's formatter to output to the Format.stdbuf string
1453 buffer.
1454 str_formatter is defined as Format.formatter_of_buffer Format.stdbuf .
1457 val get_str_formatter : unit -> formatter
1461 The current domain's formatter to output to the current domains string
1463 buffer.
1464 Since 5.0
1467 val flush_str_formatter : unit -> string
1471 Returns the material printed with str_formatter of the current domain,
1473 flushes the formatter and resets the corresponding buffer.
1474 val make_formatter : (string -> int -> int -> unit) -> (unit -> unit)
1478 -> formatter
1479 make_formatter out flush returns a new formatter that outputs with
1482 function out , and flushes with function flush .
1483 For instance,
1485 make_formatter
1486 (Stdlib.output oc)
1487 (fun () -> Stdlib.flush oc)
1488 returns a formatter to the out_channel oc .
1490 val make_synchronized_formatter : (string -> int -> int -> unit) ->
1494 (unit -> unit) -> formatter Domain.DLS.key
1495 make_synchronized_formatter out flush returns the key to the domain-lo‐
1498 cal state that holds the domain-local formatter that outputs with func‐
1499 tion out , and flushes with function flush .
1500 When the formatter is used with multiple domains, the output from the
1502 domains will be interleaved with each other at points where the format‐
1503 ter is flushed, such as with Format.print_flush .
1504 Since 5.0
1507 Alert unstable.
1510 val formatter_of_out_functions : formatter_out_functions -> formatter
1514 formatter_of_out_functions out_funs returns a new formatter that writes
1517 with the set of output functions out_funs .
1518 See definition of type Format.formatter_out_functions for the meaning
1520 of argument out_funs .
1521 Since 4.06.0
1524 Symbolic pretty-printing
1529 Symbolic pretty-printing is pretty-printing using a symbolic formatter,
1530 i.e. a formatter that outputs symbolic pretty-printing items.
1531 When using a symbolic formatter, all regular pretty-printing activities
1533 occur but output material is symbolic and stored in a buffer of output
1534 items. At the end of pretty-printing, flushing the output buffer al‐
1535 lows post-processing of symbolic output before performing low level
1536 output operations.
1537 In practice, first define a symbolic output buffer b using:
1539 - let sob = make_symbolic_output_buffer () . Then define a symbolic
1541 formatter with:
1542 - let ppf = formatter_of_symbolic_output_buffer sob
1544 Use symbolic formatter ppf as usual, and retrieve symbolic items at end
1546 of pretty-printing by flushing symbolic output buffer sob with:
1547 - flush_symbolic_output_buffer sob .
1549 type symbolic_output_item =
1552 | Output_flush (* symbolic flush command
1553 *)
1554 | Output_newline (* symbolic newline command
1555 *)
1556 | Output_string of string
1557 (* Output_string s : symbolic output for string s
1558 *)
1560 | Output_spaces of int
1561 (* Output_spaces n : symbolic command to output n spaces
1562 *)
1563 | Output_indent of int
1564 (* Output_indent i : symbolic indentation of size i
1565 *)
1567 Items produced by symbolic pretty-printers
1570 Since 4.06.0
1573 type symbolic_output_buffer
1576 The output buffer of a symbolic pretty-printer.
1579 Since 4.06.0
1582 val make_symbolic_output_buffer : unit -> symbolic_output_buffer
1586 make_symbolic_output_buffer () returns a fresh buffer for symbolic out‐
1589 put.
1590 Since 4.06.0
1593 val clear_symbolic_output_buffer : symbolic_output_buffer -> unit
1597 clear_symbolic_output_buffer sob resets buffer sob .
1600 Since 4.06.0
1603 val get_symbolic_output_buffer : symbolic_output_buffer -> sym‐
1607 bolic_output_item list
1608 get_symbolic_output_buffer sob returns the contents of buffer sob .
1611 Since 4.06.0
1614 val flush_symbolic_output_buffer : symbolic_output_buffer -> sym‐
1618 bolic_output_item list
1619 flush_symbolic_output_buffer sob returns the contents of buffer sob and
1622 resets buffer sob . flush_symbolic_output_buffer sob is equivalent to
1623 let items = get_symbolic_output_buffer sob in
1624 clear_symbolic_output_buffer sob; items
1625 Since 4.06.0
1629 val add_symbolic_output_item : symbolic_output_buffer -> symbolic_out‐
1633 put_item -> unit
1634 add_symbolic_output_item sob itm adds item itm to buffer sob .
1637 Since 4.06.0
1640 val formatter_of_symbolic_output_buffer : symbolic_output_buffer ->
1644 formatter
1645 formatter_of_symbolic_output_buffer sob returns a symbolic formatter
1648 that outputs to symbolic_output_buffer sob .
1649 Since 4.06.0
1652 Convenience formatting functions.
1657 val pp_print_list : ?pp_sep:(formatter -> unit -> unit) -> (formatter
1658 -> 'a -> unit) -> formatter -> 'a list -> unit
1659 pp_print_list ?pp_sep pp_v ppf l prints items of list l , using pp_v to
1662 print each item, and calling pp_sep between items ( pp_sep defaults to
1663 Format.pp_print_cut . Does nothing on empty lists.
1664 Since 4.02.0
1667 val pp_print_seq : ?pp_sep:(formatter -> unit -> unit) -> (formatter ->
1671 'a -> unit) -> formatter -> 'a Seq.t -> unit
1672 pp_print_seq ?pp_sep pp_v ppf s prints items of sequence s , using pp_v
1675 to print each item, and calling pp_sep between items ( pp_sep defaults
1676 to Format.pp_print_cut . Does nothing on empty sequences.
1677 This function does not terminate on infinite sequences.
1679 Since 4.12
1682 val pp_print_text : formatter -> string -> unit
1686 pp_print_text ppf s prints s with spaces and newlines respectively
1689 printed using Format.pp_print_space and Format.pp_force_newline .
1690 Since 4.02.0
1693 val pp_print_option : ?none:(formatter -> unit -> unit) -> (formatter
1697 -> 'a -> unit) -> formatter -> 'a option -> unit
1698 pp_print_option ?none pp_v ppf o prints o on ppf using pp_v if o is
1701 Some v and none if it is None . none prints nothing by default.
1702 Since 4.08
1705 val pp_print_result : ok:(formatter -> 'a -> unit) -> error:(formatter
1709 -> 'e -> unit) -> formatter -> ('a, 'e) result -> unit
1710 pp_print_result ~ok ~error ppf r prints r on ppf using ok if r is Ok _
1713 and error if r is Error _ .
1714 Since 4.08
1717 val pp_print_either : left:(formatter -> 'a -> unit) -> right:(format‐
1721 ter -> 'b -> unit) -> formatter -> ('a, 'b) Either.t -> unit
1722 pp_print_either ~left ~right ppf e prints e on ppf using left if e is
1725 Either.Left _ and right if e is Either.Right _ .
1726 Since 4.13
1729 Formatted pretty-printing
1734 Module Format provides a complete set of printf like functions for
1735 pretty-printing using format string specifications.
1736 Specific annotations may be added in the format strings to give
1738 pretty-printing commands to the pretty-printing engine.
1739 Those annotations are introduced in the format strings using the @
1741 character. For instance, @ means a space break, @, means a cut, @[
1742 opens a new box, and @] closes the last open box.
1743 val fprintf : formatter -> ('a, formatter, unit) format -> 'a
1745 fprintf ff fmt arg1 ... argN formats the arguments arg1 to argN accord‐
1751 ing to the format string fmt , and outputs the resulting string on the
1752 formatter ff .
1753 The format string fmt is a character string which contains three types
1755 of objects: plain characters and conversion specifications as specified
1756 in the Printf module, and pretty-printing indications specific to the
1757 Format module.
1758 The pretty-printing indication characters are introduced by a @ charac‐
1760 ter, and their meanings are:
1761 - @[ : open a pretty-printing box. The type and offset of the box may
1763 be optionally specified with the following syntax: the < character,
1764 followed by an optional box type indication, then an optional integer
1765 offset, and the closing > character. Pretty-printing box type is one
1766 of h , v , hv , b , or hov . ' h ' stands for an 'horizontal'
1767 pretty-printing box, ' v ' stands for a 'vertical' pretty-printing box,
1768 ' hv ' stands for an 'horizontal/vertical' pretty-printing box, ' b '
1769 stands for an 'horizontal-or-vertical' pretty-printing box demonstrat‐
1770 ing indentation, ' hov ' stands a simple 'horizontal-or-vertical'
1771 pretty-printing box. For instance, @[<hov 2> opens an 'horizon‐
1772 tal-or-vertical' pretty-printing box with indentation 2 as obtained
1773 with open_hovbox 2 . For more details about pretty-printing boxes, see
1774 the various box opening functions open_*box .
1775 - @] : close the most recently opened pretty-printing box.
1777 - @, : output a 'cut' break hint, as with print_cut () .
1779 - @ : output a 'space' break hint, as with print_space () .
1781 - @; : output a 'full' break hint as with print_break . The nspaces and
1783 offset parameters of the break hint may be optionally specified with
1784 the following syntax: the < character, followed by an integer nspaces
1785 value, then an integer offset , and a closing > character. If no pa‐
1786 rameters are provided, the good break defaults to a 'space' break hint.
1787 - @. : flush the pretty-printer and split the line, as with print_new‐
1789 line () .
1790 - @<n> : print the following item as if it were of length n . Hence,
1792 printf "@<0>%s" arg prints arg as a zero length string. If @<n> is not
1793 followed by a conversion specification, then the following character of
1794 the format is printed as if it were of length n .
1795 - @{ : open a semantic tag. The name of the tag may be optionally spec‐
1797 ified with the following syntax: the < character, followed by an op‐
1798 tional string specification, and the closing > character. The string
1799 specification is any character string that does not contain the closing
1800 character '>' . If omitted, the tag name defaults to the empty string.
1801 For more details about semantic tags, see the functions For‐
1802 mat.open_stag and Format.close_stag .
1803 - @} : close the most recently opened semantic tag.
1805 - @? : flush the pretty-printer as with print_flush () . This is
1807 equivalent to the conversion %! .
1808 - @\n : force a newline, as with force_newline () , not the normal way
1810 of pretty-printing, you should prefer using break hints inside a verti‐
1811 cal pretty-printing box.
1812 Note: To prevent the interpretation of a @ character as a pretty-print‐
1814 ing indication, escape it with a % character. Old quotation mode @@ is
1815 deprecated since it is not compatible with formatted input interpreta‐
1816 tion of character '@' .
1817 Example: printf "@[%s@ %d@]@." "x =" 1 is equivalent to open_box ();
1819 print_string "x ="; print_space ();
1820 print_int 1; close_box (); print_newline () . It prints x = 1
1821 within a pretty-printing 'horizontal-or-vertical' box.
1822 val printf : ('a, formatter, unit) format -> 'a
1824 Same as fprintf above, but output on get_std_formatter () .
1826 It is defined similarly to fun fmt -> fprintf (get_std_formatter ())
1828 fmt but delays calling get_std_formatter until after the final argument
1829 required by the format is received. When used with multiple domains,
1830 the output from the domains will be interleaved with each other at
1831 points where the formatter is flushed, such as with Format.print_flush
1832 .
1833 val eprintf : ('a, formatter, unit) format -> 'a
1837 Same as fprintf above, but output on get_err_formatter () .
1839 It is defined similarly to fun fmt -> fprintf (get_err_formatter ())
1841 fmt but delays calling get_err_formatter until after the final argument
1842 required by the format is received. When used with multiple domains,
1843 the output from the domains will be interleaved with each other at
1844 points where the formatter is flushed, such as with Format.print_flush
1845 .
1846 val sprintf : ('a, unit, string) format -> 'a
1850 Same as printf above, but instead of printing on a formatter, returns a
1852 string containing the result of formatting the arguments. Note that
1853 the pretty-printer queue is flushed at the end of each call to sprintf
1854 .
1855 In case of multiple and related calls to sprintf to output material on
1857 a single string, you should consider using fprintf with the predefined
1858 formatter str_formatter and call flush_str_formatter () to get the fi‐
1859 nal result.
1860 Alternatively, you can use Format.fprintf with a formatter writing to a
1862 buffer of your own: flushing the formatter and the buffer at the end of
1863 pretty-printing returns the desired string.
1864 val asprintf : ('a, formatter, unit, string) format4 -> 'a
1868 Same as printf above, but instead of printing on a formatter, returns a
1870 string containing the result of formatting the arguments. The type of
1871 asprintf is general enough to interact nicely with %a conversions.
1872 Since 4.01.0
1875 val dprintf : ('a, formatter, unit, formatter -> unit) format4 -> 'a
1879 Same as Format.fprintf , except the formatter is the last argument.
1881 dprintf "..." a b c is a function of type formatter -> unit which can
1882 be given to a format specifier %t .
1883 This can be used as a replacement for Format.asprintf to delay format‐
1885 ting decisions. Using the string returned by Format.asprintf in a for‐
1886 matting context forces formatting decisions to be taken in isolation,
1887 and the final string may be created prematurely. Format.dprintf allows
1888 delay of formatting decisions until the final formatting context is
1889 known. For example:
1890 let t = Format.dprintf "%i@ %i@ %i" 1 2 3 in
1891 ...
1892 Format.printf "@[<v>%t@]" t
1893 Since 4.08.0
1897 val ifprintf : formatter -> ('a, formatter, unit) format -> 'a
1901 Same as fprintf above, but does not print anything. Useful to ignore
1903 some material when conditionally printing.
1904 Since 3.10.0
1907 Formatted Pretty-Printing with continuations.
1912 val kfprintf : (formatter -> 'a) -> formatter -> ('b, formatter, unit,
1914 'a) format4 -> 'b
1915 Same as fprintf above, but instead of returning immediately, passes the
1917 formatter to its first argument at the end of printing.
1918 val kdprintf : ((formatter -> unit) -> 'a) -> ('b, formatter, unit, 'a)
1922 format4 -> 'b
1923 Same as Format.dprintf above, but instead of returning immediately,
1925 passes the suspended printer to its first argument at the end of print‐
1926 ing.
1927 Since 4.08.0
1930 val ikfprintf : (formatter -> 'a) -> formatter -> ('b, formatter, unit,
1934 'a) format4 -> 'b
1935 Same as kfprintf above, but does not print anything. Useful to ignore
1937 some material when conditionally printing.
1938 Since 3.12.0
1941 val ksprintf : (string -> 'a) -> ('b, unit, string, 'a) format4 -> 'b
1945 Same as sprintf above, but instead of returning the string, passes it
1947 to the first argument.
1948 val kasprintf : (string -> 'a) -> ('b, formatter, unit, 'a) format4 ->
1952 'b
1953 Same as asprintf above, but instead of returning the string, passes it
1955 to the first argument.
1956 Since 4.03
1959OCamldoc 2023-07-20 Format(3)