Module Base__Import0.Format
Pretty-printing.
This module implements a pretty-printing facility to format values within 'pretty-printing boxes' and 'semantic tags' combined with a set of printf-like functions. The pretty-printer splits lines at specified break hints, and indents lines according to the box structure. Similarly, semantic tags can be used to decouple text presentation from its contents.
This pretty-printing facility is implemented as an overlay on top of abstract formatters which provide basic output functions. Some formatters are predefined, notably:
Most functions in the Format
module come in two variants: a short version that operates on std_formatter
and the generic version prefixed by pp_
that takes a formatter as its first argument.
More formatters can be created with formatter_of_out_channel
, formatter_of_buffer
, formatter_of_symbolic_output_buffer
or using custom formatters.
Introduction
For a gentle introduction to the basics of pretty-printing using Format
, read http://caml.inria.fr/resources/doc/guides/format.en.html.
You may consider this module as providing an extension to the printf
facility to provide automatic line splitting. The addition of pretty-printing annotations to your regular printf
format strings 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 pretty-printing box management and printing functions provided by this module. This style is more basic but more verbose than the concise fprintf
format strings.
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 pretty-printing boxes (as obtained by
open_box 0
); - use simple break hints as obtained by
print_cut ()
that outputs a simple break hint, or byprint_space ()
that outputs a space indicating a break hint; - once a pretty-printing box is open, display its material with basic printing functions (e. g.
print_int
andprint_string
); - when the material for a pretty-printing box has been printed, call
close_box ()
to close the box; - at the end of pretty-printing, flush the pretty-printer to display all the remaining material, e.g. evaluate
print_newline ()
.
The behavior of pretty-printing commands is unspecified if there is no open pretty-printing box. Each box opened by 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, each phrase is executed in the initial state of the standard pretty-printer: after each phrase execution, the interactive system closes all open pretty-printing boxes, flushes all pending text, and resets the standard pretty-printer.
Warning: mixing calls to pretty-printing functions of this module with calls to Stdlib
low level output functions is error prone.
The pretty-printing functions output material that is delayed in the pretty-printer queue and stacks in order to compute proper line splitting. In contrast, basic I/O output functions write directly in their output device. As a consequence, the output of a basic I/O function may appear before the output of a pretty-printing function that has been called before. For instance,
Stdlib.print_string "<";
Format.print_string "PRETTY";
Stdlib.print_string ">";
Format.print_string "TEXT";
leads to output <>PRETTYTEXT
.
type formatter
Abstract data corresponding to a pretty-printer (also called a formatter) and all its machinery. See also Defining formatters.
Pretty-printing boxes
val pp_open_box : formatter -> int -> unit
val open_box : int -> unit
pp_open_box ppf d
opens a new compacting pretty-printing box with offsetd
in the formatterppf
.Within this box, the pretty-printer prints as much as possible material on every line.
A break hint splits the line if there is no more room on the line to print the remainder of the box.
Within this box, the pretty-printer emphasizes the box structure: a break hint also splits the line if the splitting ``moves to the left'' (i.e. the new line gets an indentation smaller than the one of the current line).
This box is the general purpose pretty-printing box.
If the pretty-printer splits the line in the box, offset
d
is added to the current indentation.
val pp_close_box : formatter -> unit -> unit
val close_box : unit -> unit
Closes the most recently open pretty-printing box.
val pp_open_hbox : formatter -> unit -> unit
val open_hbox : unit -> unit
pp_open_hbox ppf ()
opens a new 'horizontal' pretty-printing box.This box prints material on a single line.
Break hints in a horizontal box never split the line. (Line splitting may still occur inside boxes nested deeper).
val pp_open_vbox : formatter -> int -> unit
val open_vbox : int -> unit
pp_open_vbox ppf d
opens a new 'vertical' pretty-printing box with offsetd
.This box prints material on as many lines as break hints in the box.
Every break hint in a vertical box splits the line.
If the pretty-printer splits the line in the box,
d
is added to the current indentation.
val pp_open_hvbox : formatter -> int -> unit
val open_hvbox : int -> unit
pp_open_hvbox ppf d
opens a new 'horizontal/vertical' pretty-printing box with offsetd
.This box behaves as an horizontal box if it fits on a single line, otherwise it behaves as a vertical box.
If the pretty-printer splits the line in the box,
d
is added to the current indentation.
val pp_open_hovbox : formatter -> int -> unit
val open_hovbox : int -> unit
pp_open_hovbox ppf d
opens a new 'horizontal-or-vertical' pretty-printing box with offsetd
.This box prints material as much as possible on every line.
A break hint splits the line if there is no more room on the line to print the remainder of the box.
If the pretty-printer splits the line in the box,
d
is added to the current indentation.
Formatting functions
val pp_print_string : formatter -> string -> unit
val print_string : string -> unit
pp_print_string ppf s
printss
in the current pretty-printing box.
val pp_print_as : formatter -> int -> string -> unit
val print_as : int -> string -> unit
pp_print_as ppf len s
printss
in the current pretty-printing box. The pretty-printer formatss
as if it were of lengthlen
.
val pp_print_int : formatter -> int -> unit
val print_int : int -> unit
Print an integer in the current pretty-printing box.
val pp_print_float : formatter -> float -> unit
val print_float : float -> unit
Print a floating point number in the current pretty-printing box.
val pp_print_char : formatter -> char -> unit
val print_char : char -> unit
Print a character in the current pretty-printing box.
val pp_print_bool : formatter -> bool -> unit
val print_bool : bool -> unit
Print a boolean in the current pretty-printing box.
Break hints
val pp_print_space : formatter -> unit -> unit
val print_space : unit -> unit
pp_print_space ppf ()
emits a 'space' break hint: the pretty-printer may split the line at this point, otherwise it prints one space.pp_print_space ppf ()
is equivalent topp_print_break ppf 1 0
.
val pp_print_cut : formatter -> unit -> unit
val print_cut : unit -> unit
pp_print_cut ppf ()
emits a 'cut' break hint: the pretty-printer may split the line at this point, otherwise it prints nothing.pp_print_cut ppf ()
is equivalent topp_print_break ppf 0 0
.
val pp_print_break : formatter -> int -> int -> unit
val print_break : int -> int -> unit
pp_print_break ppf nspaces offset
emits a 'full' break hint: the pretty-printer may split the line at this point, otherwise it printsnspaces
spaces.If the pretty-printer splits the line,
offset
is added to the current indentation.
val pp_print_custom_break : formatter -> fits:(string * int * string) -> breaks:(string * int * string) -> unit
pp_print_custom_break ppf ~fits:(s1, n, s2) ~breaks:(s3, m, s4)
emits a custom break hint: the pretty-printer may split the line at this point.If it does not split the line, then the
s1
is emitted, thenn
spaces, thens2
.If it splits the line, then it emits the
s3
string, then an indent (according to the box rules), then an offset ofm
spaces, then thes4
string.While
n
andm
are handled byformatter_out_functions.out_indent
, the strings will be handled byformatter_out_functions.out_string
. This allows for a custom formatter that handles indentation distinctly, for example, outputs<br/>
tags or
entities.The custom break is useful if you want to change which visible (non-whitespace) characters are printed in case of break or no break. For example, when printing a list
[a; b; c]
, you might want to add a trailing semicolon when it is printed vertically:
[ a; b; c; ]
You can do this as follows:
printf "@[<v 0>[@;<0 2>@[<v 0>a;@,b;@,c@]%t]@]@\n" (pp_print_custom_break ~fits:("", 0, "") ~breaks:(";", 0, ""))
- since
- 4.08.0
val pp_force_newline : formatter -> unit -> unit
val force_newline : unit -> unit
Force a new line in the current pretty-printing box.
The pretty-printer must split the line at this point,
Not the normal way of pretty-printing, since imperative line splitting may interfere with current line counters and box size calculation. Using break hints within an enclosing vertical box is a better alternative.
val pp_print_if_newline : formatter -> unit -> unit
val print_if_newline : unit -> unit
Execute the next formatting command if the preceding line has just been split. Otherwise, ignore the next formatting command.
Pretty-printing termination
val pp_print_flush : formatter -> unit -> unit
val print_flush : unit -> unit
End of pretty-printing: resets the pretty-printer to initial state.
All open pretty-printing boxes are closed, all pending text is printed. In addition, the pretty-printer low level output device is flushed to ensure that all pending text is really displayed.
Note: never use
print_flush
in the normal course of a pretty-printing routine, since the pretty-printer uses a complex buffering machinery to properly indent the output; manually flushing those buffers at random would conflict with the pretty-printer strategy and result to poor rendering.Only consider using
print_flush
when displaying all pending material is mandatory (for instance in case of interactive use when you want the user to read some text) and when resetting the pretty-printer state will not disturb further pretty-printing.Warning: If the output device of the pretty-printer is an output channel, repeated calls to
print_flush
means repeated calls toStdlib.flush
to flush the out channel; these explicit flush calls could foil the buffering strategy of output channels and could dramatically impact efficiency.
val pp_print_newline : formatter -> unit -> unit
val print_newline : unit -> unit
End of pretty-printing: resets the pretty-printer to initial state.
All open pretty-printing boxes are closed, all pending text is printed.
Equivalent to
print_flush
followed by a new line. See corresponding words of caution forprint_flush
.Note: this is not the normal way to output a new line; the preferred method is using break hints within a vertical pretty-printing box.
Margin
val pp_set_margin : formatter -> int -> unit
val set_margin : int -> unit
pp_set_margin ppf d
sets the right margin tod
(in characters): the pretty-printer splits lines that overflow the right margin according to the break hints given. Nothing happens ifd
is smaller than 2. Ifd
is too large, the right margin is set to the maximum admissible value (which is greater than10 ^ 9
). Ifd
is less than the current maximum indentation limit, the maximum indentation limit is decreased while trying to preserve a minimal ratiomax_indent/margin>=50%
and if possible the current differencemargin - max_indent
.See also
pp_set_geometry
.
val pp_get_margin : formatter -> unit -> int
val get_margin : unit -> int
Returns the position of the right margin.
Maximum indentation limit
val pp_set_max_indent : formatter -> int -> unit
val set_max_indent : int -> unit
pp_set_max_indent ppf d
sets the maximum indentation limit of lines tod
(in characters): once this limit is reached, new pretty-printing boxes are rejected to the left, unless the enclosing box fully fits on the current line. As an illustration,set_margin 10; set_max_indent 5; printf "@[123456@[7@]89A@]@."
yields
123456 789A
because the nested box
"@[7@]"
is opened after the maximum indentation limit (7>5
) and its parent box does not fit on the current line. Either decreasing the length of the parent box to make it fit on a line:printf "@[123456@[7@]89@]@."
or opening an intermediary box before the maximum indentation limit which fits on the current line
printf "@[123@[456@[7@]89@]A@]@."
avoids the rejection to the left of the inner boxes and print respectively
"123456789"
and"123456789A"
. Note also that vertical boxes never fit on a line whereas horizontal boxes always fully 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 than10 ^ 9
).If
d
is greater or equal than the current margin, it is ignored, and the current maximum indentation limit is kept.See also
pp_set_geometry
.
val pp_get_max_indent : formatter -> unit -> int
val get_max_indent : unit -> int
Return the maximum indentation limit (in characters).
Geometry
Geometric functions can be used to manipulate simultaneously the coupled variables, margin and maxixum indentation limit.
val check_geometry : geometry -> bool
Check if the formatter geometry is valid:
1 < max_indent < margin
val pp_set_geometry : formatter -> max_indent:int -> margin:int -> unit
val set_geometry : max_indent:int -> margin:int -> unit
val pp_safe_set_geometry : formatter -> max_indent:int -> margin:int -> unit
val safe_set_geometry : max_indent:int -> margin:int -> unit
pp_set_geometry ppf ~max_indent ~margin
sets both the margin and maximum indentation limit forppf
.When
1 < max_indent < margin
,pp_set_geometry ppf ~max_indent ~margin
is equivalent topp_set_margin ppf margin; pp_set_max_indent ppf max_indent
; and avoids the subtly incorrectpp_set_max_indent ppf max_indent; pp_set_margin ppf margin
;Outside of this domain,
pp_set_geometry
raises an invalid argument exception whereaspp_safe_set_geometry
does nothing.- since
- 4.08.0
Maximum formatting depth
val pp_set_max_boxes : formatter -> int -> unit
val set_max_boxes : int -> unit
pp_set_max_boxes ppf max
sets the maximum number of pretty-printing boxes simultaneously open.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 pp_get_max_boxes : formatter -> unit -> int
val get_max_boxes : unit -> int
Returns the maximum number of pretty-printing boxes allowed before ellipsis.
val pp_over_max_boxes : formatter -> unit -> bool
val over_max_boxes : unit -> bool
Tests if the maximum number of pretty-printing boxes allowed have already been opened.
Tabulation boxes
val pp_open_tbox : formatter -> unit -> unit
val open_tbox : unit -> unit
open_tbox ()
opens a new tabulation box.This box prints lines separated into cells of fixed width.
Inside a tabulation box, special tabulation markers defines points of interest on the line (for instance to delimit cell boundaries). Function
Format.set_tab
sets a tabulation marker at insertion point.A tabulation box features specific tabulation breaks to move to next tabulation marker or split the line. Function
Format.print_tbreak
prints a tabulation break.
val pp_close_tbox : formatter -> unit -> unit
val close_tbox : unit -> unit
Closes the most recently opened tabulation box.
val pp_set_tab : formatter -> unit -> unit
val set_tab : unit -> unit
Sets a tabulation marker at current insertion point.
val pp_print_tab : formatter -> unit -> unit
val print_tab : unit -> unit
print_tab ()
emits a 'next' tabulation break hint: if not already set on a tabulation marker, the insertion point moves to the first tabulation marker on the right, or the pretty-printer splits the line and insertion point moves to the leftmost tabulation marker.It is equivalent to
print_tbreak 0 0
.
val pp_print_tbreak : formatter -> int -> int -> unit
val print_tbreak : int -> int -> unit
print_tbreak nspaces offset
emits a 'full' tabulation break hint.If not already set on a tabulation marker, the insertion point moves to the first tabulation marker on the right and the pretty-printer prints
nspaces
spaces.If there is no next tabulation marker on the right, the pretty-printer splits the line at this point, then insertion point moves to the leftmost tabulation marker of the box.
If the pretty-printer splits the line,
offset
is added to the current indentation.
Ellipsis
val pp_set_ellipsis_text : formatter -> string -> unit
val set_ellipsis_text : string -> unit
Set the text of the ellipsis printed when too many pretty-printing boxes are open (a single dot,
.
, by default).
val pp_get_ellipsis_text : formatter -> unit -> string
val get_ellipsis_text : unit -> string
Return the text of the ellipsis.
Semantic tags
type stag
=
..
Semantic tags (or simply tags) are user's defined annotations to associate user's specific operations to printed entities.
Common usage of semantic tags is text decoration to get specific font or text size rendering for a display device, or marking delimitation of entities (e.g. HTML or TeX elements or terminal escape sequences). More sophisticated usage of semantic tags could handle dynamic modification of the pretty-printer behavior to properly print the material within some specific tags. For instance, we can define an RGB tag like so:
type stag += RGB of {r:int;g:int;b:int}
In order to properly delimit printed entities, a semantic tag must be opened before and closed after the entity. Semantic tags must be properly nested like parentheses using
pp_open_stag
andpp_close_stag
.Tag specific operations occur any time a tag is opened or closed, At each occurrence, two kinds of operations are performed tag-marking and tag-printing:
- The tag-marking operation is the simpler tag specific operation: it simply writes a tag specific string into the output device of the formatter. Tag-marking does not interfere with line-splitting computation.
- The tag-printing operation is the more involved tag specific operation: it can print arbitrary material to the formatter. Tag-printing is tightly linked to the current pretty-printer operations.
Roughly speaking, tag-marking is commonly used to get a better rendering of texts in the rendering device, while tag-printing allows fine tuning of printing routines to print the same entity differently according to the semantic tags (i.e. print additional material or even omit parts of the output).
More precisely: when a semantic tag is opened or closed then both and successive 'tag-printing' and 'tag-marking' operations occur:
- Tag-printing a semantic tag means calling the formatter specific function
print_open_stag
(resp.print_close_stag
) 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 splitting computation). - Tag-marking a semantic tag means calling the formatter specific function
mark_open_stag
(resp.mark_close_stag
) with the name of the tag as argument: that tag-marking function can then return the 'tag-opening marker' (resp. `tag-closing marker') for direct output into the output device of the formatter.
Being written directly into the output device of the formatter, semantic tag marker strings are not considered as part of the printing material that drives line splitting (in other words, the length of the strings corresponding to tag markers is considered as zero for line splitting).
Thus, semantic tag handling is in some sense transparent to pretty-printing and does not interfere with usual indentation. 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 totrue
, the pretty-printer engine honors tags and decorates the output accordingly.Default tag-marking functions behave the HTML way: string tags are enclosed in "<" and ">" while other tags are ignored; hence, opening marker for tag string
"t"
is"<t>"
and closing marker is"</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_stag_functions
.Semantic tag operations may be set on or off with
set_tags
. Tag-marking operations may be set on or off withset_mark_tags
. Tag-printing operations may be set on or off withset_print_tags
.
val pp_open_stag : formatter -> stag -> unit
val open_stag : stag -> unit
pp_open_stag ppf t
opens the semantic tag namedt
.The
print_open_stag
tag-printing function of the formatter is called witht
as argument; then the opening tag marker fort
, as given bymark_open_stag t
, is written into the output device of the formatter.
val pp_close_stag : formatter -> unit -> unit
val close_stag : unit -> unit
pp_close_stag ppf ()
closes the most recently opened semantic tagt
.The closing tag marker, as given by
mark_close_stag t
, is written into the output device of the formatter; then theprint_close_stag
tag-printing function of the formatter is called witht
as argument.
val pp_set_tags : formatter -> bool -> unit
val set_tags : bool -> unit
pp_set_tags ppf b
turns on or off the treatment of semantic tags (default is off).
val pp_set_print_tags : formatter -> bool -> unit
val set_print_tags : bool -> unit
pp_set_print_tags ppf b
turns on or off the tag-printing operations.
val pp_set_mark_tags : formatter -> bool -> unit
val set_mark_tags : bool -> unit
pp_set_mark_tags ppf b
turns on or off the tag-marking operations.
val pp_get_print_tags : formatter -> unit -> bool
val get_print_tags : unit -> bool
Return the current status of tag-printing operations.
val pp_get_mark_tags : formatter -> unit -> bool
val get_mark_tags : unit -> bool
Return the current status of tag-marking operations.
val pp_set_formatter_out_channel : formatter -> Stdlib.out_channel -> unit
Redirecting the standard formatter output
val set_formatter_out_channel : Stdlib.out_channel -> unit
Redirect the standard 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.)
set_formatter_out_channel
is equivalent topp_set_formatter_out_channel
std_formatter
.
val pp_set_formatter_output_functions : formatter -> (string -> int -> int -> unit) -> (unit -> unit) -> unit
val set_formatter_output_functions : (string -> int -> int -> unit) -> (unit -> unit) -> unit
pp_set_formatter_output_functions ppf out flush
redirects the standard pretty-printer output functions to the functionsout
andflush
.The
out
function performs all the pretty-printer string output. It is called with a strings
, a start positionp
, and a number of charactersn
; it is supposed to output charactersp
top + n - 1
ofs
.The
flush
function is called whenever the pretty-printer is flushed (via conversion%!
, or pretty-printing indications@?
or@.
, or using low level functionsprint_flush
orprint_newline
).
val pp_get_formatter_output_functions : formatter -> unit -> (string -> int -> int -> unit) * (unit -> unit)
val get_formatter_output_functions : unit -> (string -> int -> int -> unit) * (unit -> unit)
Return the current output functions of the standard pretty-printer.
Redefining formatter output
Redefining output functions
type formatter_out_functions
=
{
out_string : string -> int -> int -> unit;
out_flush : unit -> unit;
out_newline : unit -> unit;
out_spaces : int -> unit;
out_indent : int -> unit;
}
The set of output functions specific to a formatter:
- the
out_string
function performs all the pretty-printer string output. It is called with a strings
, a start positionp
, and a number of charactersn
; it is supposed to output charactersp
top + n - 1
ofs
. - the
out_flush
function flushes the pretty-printer output device. out_newline
is called to open a new line when the pretty-printer splits the line.- the
out_spaces
function outputs spaces when a break hint leads to spaces instead of a line split. It is called with the number of spaces to output. - the
out_indent
function performs new line indentation when the pretty-printer splits the line. It is called with the indentation value of the new line.
By default:
- fields
out_string
andout_flush
are output device specific; (e.g.Stdlib.output_string
andStdlib.flush
for aStdlib.out_channel
device, orBuffer.add_substring
andStdlib.ignore
for aBuffer.t
output device), - field
out_newline
is equivalent toout_string "\n" 0 1
; - fields
out_spaces
andout_indent
are equivalent toout_string (String.make n ' ') 0 n
.
- since
- 4.01.0
- the
val pp_set_formatter_out_functions : formatter -> formatter_out_functions -> unit
val set_formatter_out_functions : formatter_out_functions -> unit
pp_set_formatter_out_functions ppf out_funs
Set all the pretty-printer output functions ofppf
to those of argumentout_funs
,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).
Reasonable defaults for functions
out_spaces
andout_newline
are respectivelyout_funs.out_string (String.make n ' ') 0 n
andout_funs.out_string "\n" 0 1
.- since
- 4.01.0
val pp_get_formatter_out_functions : formatter -> unit -> formatter_out_functions
val get_formatter_out_functions : unit -> formatter_out_functions
Return the current output functions of the pretty-printer, including line splitting and indentation functions. Useful to record the current setting and restore it afterwards.
- since
- 4.01.0
Redefining semantic tag operations
type formatter_stag_functions
=
{
mark_open_stag : stag -> string;
mark_close_stag : stag -> string;
print_open_stag : stag -> unit;
print_close_stag : stag -> unit;
}
The semantic 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 write 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 pp_set_formatter_stag_functions : formatter -> formatter_stag_functions -> unit
val set_formatter_stag_functions : formatter_stag_functions -> unit
pp_set_formatter_stag_functions ppf tag_funs
changes the meaning of opening and closing semantic tag operations to use the functions intag_funs
when printing onppf
.When opening a semantic tag with name
t
, the stringt
is passed to the opening tag-marking function (themark_open_stag
field of the recordtag_funs
), that must return the opening tag marker for that name. When the next call toclose_stag ()
happens, the semantic tag namet
is sent back to the closing tag-marking function (themark_close_stag
field of recordtag_funs
), that must return a closing tag marker for that name.The
print_
field of the record contains the tag-printing functions that are called at tag opening and tag closing time, to output regular material in the pretty-printer queue.
val pp_get_formatter_stag_functions : formatter -> unit -> formatter_stag_functions
val get_formatter_stag_functions : unit -> formatter_stag_functions
Return the current semantic tag operation functions of the standard pretty-printer.
Defining formatters
Defining new formatters permits unrelated output of material in parallel on several output devices. All the parameters of a formatter are local to the formatter: right margin, maximum indentation limit, maximum number of pretty-printing boxes simultaneously open, ellipsis, and so on, are specific to each formatter and may be fixed independently.
For instance, given a Buffer
.t buffer b
, formatter_of_buffer
b
returns a new formatter using buffer b
as its output device. Similarly, given a Stdlib.out_channel
output channel oc
, formatter_of_out_channel
oc
returns a new formatter using channel oc
as its output device.
Alternatively, given out_funs
, a complete set of output functions for a formatter, then formatter_of_out_functions
out_funs
computes a new formatter using those functions for output.
val formatter_of_out_channel : Stdlib.out_channel -> formatter
formatter_of_out_channel oc
returns a new formatter writing to the corresponding output channeloc
.
val std_formatter : formatter
The standard formatter to write to standard output.
It is defined as
formatter_of_out_channel
Stdlib.stdout
.
val err_formatter : formatter
A formatter to write to standard error.
It is defined as
formatter_of_out_channel
Stdlib.stderr
.
val formatter_of_buffer : Stdlib.Buffer.t -> formatter
formatter_of_buffer b
returns a new formatter writing to bufferb
. At the end of pretty-printing, the formatter must be flushed usingpp_print_flush
orpp_print_newline
, to print all the pending material into the buffer.
val stdbuf : Stdlib.Buffer.t
The string buffer in which
str_formatter
writes.
val str_formatter : formatter
A formatter to output to the
stdbuf
string buffer.str_formatter
is defined asformatter_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 outputs with functionout
, and flushes with functionflush
.For instance,
make_formatter (Stdlib.output oc) (fun () -> Stdlib.flush oc)
returns a formatter to the
Stdlib.out_channel
oc
.
val formatter_of_out_functions : formatter_out_functions -> formatter
formatter_of_out_functions out_funs
returns a new formatter that writes with the set of output functionsout_funs
.See definition of type
formatter_out_functions
for the meaning of argumentout_funs
.- since
- 4.06.0
Symbolic pretty-printing
type symbolic_output_item
=
Items produced by symbolic pretty-printers
- since
- 4.06.0
val make_symbolic_output_buffer : unit -> symbolic_output_buffer
make_symbolic_output_buffer ()
returns a fresh buffer for symbolic output.- since
- 4.06.0
val clear_symbolic_output_buffer : symbolic_output_buffer -> unit
clear_symbolic_output_buffer sob
resets buffersob
.- since
- 4.06.0
val get_symbolic_output_buffer : symbolic_output_buffer -> symbolic_output_item list
get_symbolic_output_buffer sob
returns the contents of buffersob
.- since
- 4.06.0
val flush_symbolic_output_buffer : symbolic_output_buffer -> symbolic_output_item list
flush_symbolic_output_buffer sob
returns the contents of buffersob
and resets buffersob
.flush_symbolic_output_buffer sob
is equivalent tolet items = get_symbolic_output_buffer sob in clear_symbolic_output_buffer sob; items
- since
- 4.06.0
val add_symbolic_output_item : symbolic_output_buffer -> symbolic_output_item -> unit
add_symbolic_output_item sob itm
adds itemitm
to buffersob
.- since
- 4.06.0
val formatter_of_symbolic_output_buffer : symbolic_output_buffer -> formatter
formatter_of_symbolic_output_buffer sob
returns a symbolic formatter that outputs tosymbolic_output_buffer
sob
.- since
- 4.06.0
Convenience formatting functions.
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 items of listl
, usingpp_v
to print each item, and callingpp_sep
between items (pp_sep
defaults topp_print_cut
. Does nothing on empty lists.- since
- 4.02.0
val pp_print_text : formatter -> string -> unit
pp_print_text ppf s
printss
with spaces and newlines respectively printed usingpp_print_space
andpp_force_newline
.- since
- 4.02.0
val pp_print_option : ?none:(formatter -> unit -> unit) -> (formatter -> 'a -> unit) -> formatter -> 'a option -> unit
pp_print_option ?none pp_v ppf o
printso
onppf
usingpp_v
ifo
isSome v
andnone
if it isNone
.none
prints nothing by default.- since
- 4.08
val pp_print_result : ok:(formatter -> 'a -> unit) -> error:(formatter -> 'e -> unit) -> formatter -> ('a, 'e) Stdlib.result -> unit
pp_print_result ~ok ~error ppf r
printsr
onppf
usingok
ifr
isOk _
anderror
ifr
isError _
.- since
- 4.08
Formatted pretty-printing
val fprintf : formatter -> ('a, formatter, unit) Stdlib.format -> 'a
val printf : ('a, formatter, unit) Stdlib.format -> 'a
Same as
fprintf
above, but output onstd_formatter
.
val eprintf : ('a, formatter, unit) Stdlib.format -> 'a
Same as
fprintf
above, but output onerr_formatter
.
val sprintf : ('a, unit, string) Stdlib.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 each call tosprintf
.In case of multiple and related calls to
sprintf
to output material on a single string, you should consider usingfprintf
with the predefined formatterstr_formatter
and callflush_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) Stdlib.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 ofasprintf
is general enough to interact nicely with%a
conversions.- since
- 4.01.0
val dprintf : ('a, formatter, unit, formatter -> unit) Stdlib.format4 -> 'a
Same as
fprintf
, except the formatter is the last argument.dprintf "..." a b c
is a function of typeformatter -> unit
which can be given to a format specifier%t
.This can be used as a replacement for
asprintf
to delay formatting decisions. Using the string returned byasprintf
in a formatting context forces formatting decisions to be taken in isolation, and the final string may be created prematurely.dprintf
allows delay of formatting decisions until the final formatting context is known. For example:let t = Format.dprintf "%i@ %i@ %i" 1 2 3 in ... Format.printf "@[<v>%t@]" t
- since
- 4.08.0
val ifprintf : formatter -> ('a, formatter, unit) Stdlib.format -> 'a
Same as
fprintf
above, but does not print anything. Useful to ignore some material when conditionally printing.- since
- 3.10.0
val kfprintf : (formatter -> 'a) -> formatter -> ('b, formatter, unit, 'a) Stdlib.format4 -> 'b
Same as
fprintf
above, but instead of returning immediately, passes the formatter to its first argument at the end of printing.
val kdprintf : ((formatter -> unit) -> 'a) -> ('b, formatter, unit, 'a) Stdlib.format4 -> 'b
Same as
dprintf
above, but instead of returning immediately, passes the suspended printer to its first argument at the end of printing.- since
- 4.08.0
val ikfprintf : (formatter -> 'a) -> formatter -> ('b, formatter, unit, 'a) Stdlib.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) Stdlib.format4 -> 'b
Same as
sprintf
above, but instead of returning the string, passes it to the first argument.
val kasprintf : (string -> 'a) -> ('b, formatter, unit, 'a) Stdlib.format4 -> 'b
Same as
asprintf
above, but instead of returning the string, passes it to the first argument.- since
- 4.03
Deprecated
val bprintf : Stdlib.Buffer.t -> ('a, formatter, unit) Stdlib.format -> 'a
- deprecated
This function is error prone. Do not use it. This function is neither compositional nor incremental, since it flushes the pretty-printer queue at each call.
If you need to print to some buffer
b
, you must first define a formatter writing tob
, usinglet to_b = formatter_of_buffer b
; then use regular calls toFormat.fprintf
with formatterto_b
.
val kprintf : (string -> 'a) -> ('b, unit, string, 'a) Stdlib.format4 -> 'b
- deprecated
An alias for
ksprintf
.
val set_all_formatter_output_functions : out:(string -> int -> int -> unit) -> flush:(unit -> unit) -> newline:(unit -> unit) -> spaces:(int -> unit) -> unit
- deprecated
Subsumed by
set_formatter_out_functions
.
val get_all_formatter_output_functions : unit -> (string -> int -> int -> unit) * (unit -> unit) * (unit -> unit) * (int -> unit)
- deprecated
Subsumed by
get_formatter_out_functions
.
val pp_set_all_formatter_output_functions : formatter -> out:(string -> int -> int -> unit) -> flush:(unit -> unit) -> newline:(unit -> unit) -> spaces:(int -> unit) -> unit
- deprecated
Subsumed by
pp_set_formatter_out_functions
.
val pp_get_all_formatter_output_functions : formatter -> unit -> (string -> int -> int -> unit) * (unit -> unit) * (unit -> unit) * (int -> unit)
- deprecated
Subsumed by
pp_get_formatter_out_functions
.
String tags
val open_tag : tag -> unit
- deprecated
Subsumed by
open_stag
.
val pp_close_tag : formatter -> unit -> unit
- deprecated
Subsumed by
pp_close_stag
.
type formatter_tag_functions
=
{
mark_open_tag : tag -> string;
mark_close_tag : tag -> string;
print_open_tag : tag -> unit;
print_close_tag : tag -> unit;
}
- deprecated
Subsumed by
formatter_stag_functions
.
val pp_set_formatter_tag_functions : formatter -> formatter_tag_functions -> unit
This function will erase non-string tag formatting functions.
- deprecated
Subsumed by
pp_set_formatter_stag_functions
.
val set_formatter_tag_functions : formatter_tag_functions -> unit
- deprecated
Subsumed by
set_formatter_stag_functions
.
val pp_get_formatter_tag_functions : formatter -> unit -> formatter_tag_functions
- deprecated
Subsumed by
pp_get_formatter_stag_functions
.
val get_formatter_tag_functions : unit -> formatter_tag_functions
- deprecated
Subsumed by
get_formatter_stag_functions
.