module Format:sig
..end
This module implements a pretty-printing facility to format values within 'pretty-printing boxes'. The pretty-printer splits lines at specified break hints, and indents lines according to the box structure.
For a gentle introduction to the basics of pretty-printing using
Format
, read
http://caml.inria.fr/resources/doc/guides/format.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
formats gives you
fancy indentation and line breaks.
Pretty-printing annotations are described below in the documentation of
the function Format.fprintf
.
You may also use the explicit box management and printing functions
provided by this module. This style is more basic but more verbose
than the fprintf
concise formats.
For instance, the sequence
open_box 0; print_string "x ="; print_space ();
that prints
print_int 1; close_box (); print_newline ()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:
open_box 0
);print_cut ()
that outputs a
simple break hint, or by print_space ()
that outputs a space
indicating a break hint);print_int
and print_string
);close_box ()
to
close the box;print_newline ()
.open_
functions below must be closed using close_box
for proper formatting. Otherwise, some of the material printed in the
boxes may not be output, or may be formatted incorrectly.
In case of interactive use, the system closes all opened boxes and
flushes all pending text (as with the print_newline
function)
after each phrase. Each phrase is therefore executed in the initial
state of the pretty-printer.
Warning: the material output by the following functions is delayed in the pretty-printer queue in order to compute the proper line splitting. Hence, you should not mix calls to the printing functions of the basic I/O system with calls to the functions of this module: this could result in some strange output seemingly unrelated with the evaluation order of printing commands.
val open_box : int -> unit
open_box d
opens a new pretty-printing box
with offset d
.
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. A break hint also splits the line if the splitting ``moves to the left'' (i.e. it gives 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 close_box : unit -> unit
val print_string : string -> unit
print_string str
prints str
in the current box.val print_as : int -> string -> unit
print_as len str
prints str
in the
current box. The pretty-printer formats str
as if
it were of length len
.val print_int : int -> unit
val print_float : float -> unit
val print_char : char -> unit
val print_bool : bool -> unit
Break hints are used to separate printing items and are mandatory to let the pretty-printer correctly split lines and indent items.
Simple break hints are:
val print_space : unit -> unit
print_space ()
the 'space' break hint:
the pretty-printer may split the line at this
point, otherwise it prints one space.
It is equivalent to print_break 1 0
.val print_cut : unit -> unit
print_cut ()
the 'cut' break hint:
the pretty-printer may split the line at this
point, otherwise it prints nothing.
It is equivalent to print_break 0 0
.val print_break : int -> int -> unit
print_break nspaces offset
the 'full' break hint:
the pretty-printer may split the line at this
point, otherwise it prints nspaces
spaces.
If the pretty-printer splits the line, offset
is added to
the current indentation.
val print_flush : unit -> unit
val print_newline : unit -> unit
print_flush
followed by a new line.val force_newline : unit -> unit
val print_if_newline : unit -> unit
val set_margin : int -> unit
set_margin d
sets the right margin to d
(in characters):
the pretty-printer splits lines that overflow the right margin according to
the break hints given.
Nothing happens if d
is smaller than 2.
If d
is too large, the right margin is set to the maximum
admissible value (which is greater than 10^9
).val get_margin : unit -> int
val set_max_indent : int -> unit
set_max_indent d
sets the maximum indentation limit of lines to d
(in
characters):
once this limit is reached, new boxes are rejected to the left,
if they do not fit on the current line.
Nothing happens if d
is smaller than 2.
If d
is too large, the limit is set to the maximum
admissible value (which is greater than 10 ^ 9
).val get_max_indent : unit -> int
val set_max_boxes : int -> unit
set_max_boxes max
sets the maximum number of boxes simultaneously
opened.
Material inside boxes nested deeper is printed as an ellipsis (more
precisely as the text returned by get_ellipsis_text ()
).
Nothing happens if max
is smaller than 2.val get_max_boxes : unit -> int
val over_max_boxes : unit -> bool
val open_hbox : unit -> unit
open_hbox ()
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 open_vbox : int -> unit
open_vbox d
opens a new 'vertical' pretty-printing box
with offset d
.
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 open_hvbox : int -> unit
open_hvbox d
opens a new 'horizontal-vertical' pretty-printing box
with offset d
.
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 open_hovbox : int -> unit
open_hovbox d
opens a new 'horizontal-or-vertical' pretty-printing box
with offset d
.
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.
val set_ellipsis_text : string -> unit
.
, by default).val get_ellipsis_text : unit -> string
typeSemantic tags (or simply tags) are used to decorate printed entities for user's defined purposes, e.g. setting font and giving size indications for a display device, or marking delimitation of semantic entities (e.g. HTML or TeX elements or terminal escape sequences).tag =
string
By default, those tags do not influence line splitting calculation: the tag 'markers' are not considered as part of the printing material that drives line splitting (in other words, the length of those strings is considered as zero for line splitting).
Thus, 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 to true
,
the pretty printer engine honours tags and decorates the output
accordingly.
When a tag has been opened (or closed), it is both and successively 'printed' and 'marked'. Printing a tag means calling a formatter specific function with the name of the tag as argument: that 'tag printing' function can then print any regular material to the formatter (so that this material is enqueued as usual in the formatter queue for further line splitting computation). Marking a tag means to output an arbitrary string (the 'tag marker'), directly into the output device of the formatter. Hence, the formatter specific 'tag marking' function must return the tag marker string associated to its tag argument. Being flushed directly into the output device of the formatter, tag marker strings are not considered as part of the printing material that drives line splitting (in other words, the length of the strings corresponding to tag markers is considered as zero for line splitting). In addition, advanced users may take advantage of the specificity of tag markers to be precisely output when the pretty printer has already decided where to split the lines, and precisely when the queue is flushed into the output device.
In the spirit of HTML tags, the default tag marking functions
output tags enclosed in "<" and ">": hence, the opening marker of
tag t
is "<t>"
and the closing marker "</t>"
.
Default tag printing functions just do nothing.
Tag marking and tag printing functions are user definable and can
be set by calling set_formatter_tag_functions
.
val open_tag : tag -> unit
open_tag t
opens the tag named t
; the print_open_tag
function of the formatter is called with t
as argument;
the tag marker mark_open_tag t
will be flushed into the output
device of the formatter.val close_tag : unit -> unit
close_tag ()
closes the most recently opened tag t
.
In addition, the print_close_tag
function of the formatter is called
with t
as argument. The marker mark_close_tag t
will be flushed
into the output device of the formatter.bool -> unit
: set_tags b
turns on or off the treatment of tags (default is off).bool -> unit
: set_print_tags b
turns on or off the printing of tags.bool -> unit
: set_mark_tags b
turns on or off the output of tag markers.unit -> bool
: unit -> bool
: val set_formatter_out_channel : out_channel -> unit
val set_formatter_output_functions : (string -> int -> int -> unit) -> (unit -> unit) -> unit
set_formatter_output_functions out flush
redirects the
pretty-printer output functions to the functions out
and
flush
.
The out
function performs all the pretty-printer string output.
It is called with a string s
, a start position p
, and a number of
characters n
; it is supposed to output characters p
to p + n - 1
of
s
.
The flush
function is called whenever the pretty-printer is flushed
(via conversion %!
, or pretty-printing indications @?
or @.
, or
using low level functions print_flush
or print_newline
).
val get_formatter_output_functions : unit -> (string -> int -> int -> unit) * (unit -> unit)
Format
module is versatile enough to let you completely redefine
the meaning of pretty printing: you may provide your own functions to define
how to handle indentation, line splitting, and even printing of all the
characters that have to be printed!
type
formatter_out_functions = {
|
out_string : |
|
out_flush : |
|
out_newline : |
|
out_spaces : |
val set_formatter_out_functions : formatter_out_functions -> unit
set_formatter_out_functions f
Redirect the pretty-printer output to the functions f.out_string
and f.out_flush
as described in
set_formatter_output_functions
. In addition, the pretty-printer function
that outputs a newline is set to the function f.out_newline
and
the function that outputs indentation spaces is set to the function
f.out_spaces
.
This way, you can change the meaning of indentation (which can be
something else than just printing space characters) and the meaning of new
lines opening (which can be connected to any other action needed by the
application at hand). The two functions f.out_spaces
and f.out_newline
are normally connected to f.out_string
and f.out_flush
: respective
default values for f.out_space
and f.out_newline
are
f.out_string (String.make n ' ') 0 n
and f.out_string "\n" 0 1
.
val get_formatter_out_functions : unit -> formatter_out_functions
type
formatter_tag_functions = {
|
mark_open_tag : |
|
mark_close_tag : |
|
print_open_tag : |
|
print_close_tag : |
mark
versions are the 'tag marking' functions that associate a string
marker to a tag in order for the pretty-printing engine to flush
those markers as 0 length tokens in the output device of the formatter.
print
versions are the 'tag printing' functions that can perform
regular printing when a tag is closed or opened.val set_formatter_tag_functions : formatter_tag_functions -> unit
set_formatter_tag_functions tag_funs
changes the meaning of
opening and closing tags to use the functions in tag_funs
.
When opening a tag name t
, the string t
is passed to the
opening tag marking function (the mark_open_tag
field of the
record tag_funs
), that must return the opening tag marker for
that name. When the next call to close_tag ()
happens, the tag
name t
is sent back to the closing tag marking function (the
mark_close_tag
field of record tag_funs
), that must return a
closing tag marker for that name.
The print_
field of the record contains the functions that are
called at tag opening and tag closing time, to output regular
material in the pretty-printer queue.
val get_formatter_tag_functions : unit -> formatter_tag_functions
type
formatter
Defining new pretty-printers permits unrelated output of material in
parallel on several output channels.
All the parameters of a pretty-printer are local to a formatter:
margin, maximum indentation limit, maximum number of boxes
simultaneously opened, ellipsis, and so on, are specific to
each pretty-printer and may be fixed independently.
Given a Pervasives.out_channel
output channel oc
, a new formatter
writing to that channel is simply obtained by calling
formatter_of_out_channel oc
.
Alternatively, the make_formatter
function allocates a new
formatter with explicit output and flushing functions
(convenient to output material to strings for instance).
val formatter_of_out_channel : out_channel -> formatter
formatter_of_out_channel oc
returns a new formatter that
writes to the corresponding channel oc
.val std_formatter : formatter
formatter_of_out_channel stdout
.val err_formatter : formatter
formatter_of_out_channel stderr
.val formatter_of_buffer : Buffer.t -> formatter
formatter_of_buffer b
returns a new formatter writing to
buffer b
. As usual, the formatter has to be flushed at
the end of pretty printing, using pp_print_flush
or
pp_print_newline
, to display all the pending material.val stdbuf : Buffer.t
str_formatter
writes.val str_formatter : formatter
stdbuf
string buffer.
str_formatter
is defined as formatter_of_buffer stdbuf
.val flush_str_formatter : unit -> string
str_formatter
, flushes
the formatter and resets the corresponding buffer.val make_formatter : (string -> int -> int -> unit) -> (unit -> unit) -> formatter
make_formatter out flush
returns a new formatter that writes according
to the output function out
, and the flushing function flush
. For
instance, a formatter to the Pervasives.out_channel
oc
is returned by
make_formatter (Pervasives.output oc) (fun () -> Pervasives.flush oc)
.val pp_open_hbox : formatter -> unit -> unit
val pp_open_vbox : formatter -> int -> unit
val pp_open_hvbox : formatter -> int -> unit
val pp_open_hovbox : formatter -> int -> unit
val pp_open_box : formatter -> int -> unit
val pp_close_box : formatter -> unit -> unit
val pp_open_tag : formatter -> string -> unit
val pp_close_tag : formatter -> unit -> unit
val pp_print_string : formatter -> string -> unit
val pp_print_as : formatter -> int -> string -> unit
val pp_print_int : formatter -> int -> unit
val pp_print_float : formatter -> float -> unit
val pp_print_char : formatter -> char -> unit
val pp_print_bool : formatter -> bool -> unit
val pp_print_break : formatter -> int -> int -> unit
val pp_print_cut : formatter -> unit -> unit
val pp_print_space : formatter -> unit -> unit
val pp_force_newline : formatter -> unit -> unit
val pp_print_flush : formatter -> unit -> unit
val pp_print_newline : formatter -> unit -> unit
val pp_print_if_newline : formatter -> unit -> unit
formatter -> bool -> unit
: formatter -> bool -> unit
: formatter -> bool -> unit
: formatter -> unit -> bool
: formatter -> unit -> bool
: val pp_set_margin : formatter -> int -> unit
val pp_get_margin : formatter -> unit -> int
val pp_set_max_indent : formatter -> int -> unit
val pp_get_max_indent : formatter -> unit -> int
val pp_set_max_boxes : formatter -> int -> unit
val pp_get_max_boxes : formatter -> unit -> int
val pp_over_max_boxes : formatter -> unit -> bool
val pp_set_ellipsis_text : formatter -> string -> unit
val pp_get_ellipsis_text : formatter -> unit -> string
val pp_set_formatter_out_channel : formatter -> out_channel -> unit
val pp_set_formatter_output_functions : formatter -> (string -> int -> int -> unit) -> (unit -> unit) -> unit
val pp_get_formatter_output_functions : formatter -> unit -> (string -> int -> int -> unit) * (unit -> unit)
val pp_set_formatter_tag_functions : formatter -> formatter_tag_functions -> unit
val pp_get_formatter_tag_functions : formatter -> unit -> formatter_tag_functions
val pp_set_formatter_out_functions : formatter -> formatter_out_functions -> unit
val pp_get_formatter_out_functions : formatter -> unit -> formatter_out_functions
print_string
is equal to pp_print_string std_formatter
.val pp_flush_formatter : formatter -> unit
pp_flush_formatter fmt
flushes fmt
's internal queue, ensuring that all
the printing and flushing actions have been performed. In addition, this
operation will close all boxes and reset the state of the formatter.
This will not flush fmt
's output. In most cases, the user may want to use
Format.pp_print_flush
instead.
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 list l
,
using pp_v
to print each item, and calling pp_sep
between items (pp_sep
defaults to Format.pp_print_cut
).
Does nothing on empty lists.val pp_print_text : formatter -> string -> unit
pp_print_text ppf s
prints s
with spaces and newlines
respectively printed with Format.pp_print_space
and
Format.pp_force_newline
.printf
like functions for pretty-printing.val fprintf : formatter -> ('a, formatter, unit) format -> 'a
fprintf ff fmt arg1 ... argN
formats the arguments arg1
to argN
according to the format string fmt
, and outputs the resulting string on
the formatter ff
.
The format fmt
is a character string which contains three types of
objects: plain characters and conversion specifications as specified in
the Printf
module, and pretty-printing indications specific to the
Format
module.
The pretty-printing indication characters are introduced by
a @
character, and their meanings are:
@[
: open a pretty-printing box. The type and offset of the
box may be optionally specified with the following syntax:
the <
character, followed by an optional box type indication,
then an optional integer offset, and the closing >
character.
Box type is one of h
, v
, hv
, b
, or hov
.
'h
' stands for an 'horizontal' box,
'v
' stands for a 'vertical' box,
'hv
' stands for an 'horizontal-vertical' box,
'b
' stands for an 'horizontal-or-vertical' box demonstrating indentation,
'hov
' stands a simple 'horizontal-or-vertical' box.
For instance, @[<hov 2>
opens an 'horizontal-or-vertical'
box with indentation 2 as obtained with open_hovbox 2
.
For more details about boxes, see the various box opening
functions open_*box
.@]
: close the most recently opened pretty-printing box.@,
: output a 'cut' break hint, as with print_cut ()
.@
: output a 'space' break hint, as with print_space ()
.@;
: output a 'full' break hint as with print_break
. The
nspaces
and offset
parameters of the break hint may be
optionally specified with the following syntax:
the <
character, followed by an integer nspaces
value,
then an integer offset
, and a closing >
character.
If no parameters are provided, the good break defaults to a
'space' break hint.@.
: flush the pretty printer and split the line, as with
print_newline ()
.@<n>
: print the following item as if it were of length n
.
Hence, printf "@<0>%s" arg
prints arg
as a zero length string.
If @<n>
is not followed by a conversion specification,
then the following character of the format is printed as if
it were of length n
.@{
: open a tag. The name of the tag may be optionally
specified with the following syntax:
the <
character, followed by an optional string
specification, and the closing >
character. The string
specification is any character string that does not contain the
closing character '>'
. If omitted, the tag name defaults to the
empty string.
For more details about tags, see the functions open_tag
and
close_tag
.@}
: close the most recently opened tag.@?
: flush the pretty printer as with print_flush ()
.
This is equivalent to the conversion %!
.@\n
: force a newline, as with force_newline ()
, not the normal way
of pretty-printing, you should prefer using break hints inside a vertical
box.@
character as a
pretty-printing indication, you must escape it with a %
character.
Old quotation mode @@
is deprecated since it is not compatible with
formatted input interpretation of character '@'
.
Example: printf "@[%s@ %d@]@." "x =" 1
is equivalent to
open_box (); print_string "x ="; print_space ();
.
It prints
print_int 1; close_box (); print_newline ()x = 1
within a pretty-printing 'horizontal-or-vertical' box.
val printf : ('a, formatter, unit) format -> 'a
fprintf
above, but output on std_formatter
.val eprintf : ('a, formatter, unit) format -> 'a
fprintf
above, but output on err_formatter
.val sprintf : ('a, unit, string) format -> 'a
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 to sprintf
.
In case of multiple and related calls to sprintf
to output
material on a single string, you should consider using fprintf
with the predefined formatter str_formatter
and call
flush_str_formatter ()
to get the final result.
Alternatively, you can use Format.fprintf
with a formatter writing to a
buffer of your own: flushing the formatter and the buffer at the end of
pretty-printing returns the desired string.
val asprintf : ('a, formatter, unit, string) format4 -> 'a
printf
above, but instead of printing on a formatter,
returns a string containing the result of formatting the arguments.
The type of asprintf
is general enough to interact nicely with %a
conversions.val ifprintf : formatter -> ('a, formatter, unit) format -> 'a
fprintf
above, but does not print anything.
Useful to ignore some material when conditionally printing.val kfprintf : (formatter -> 'a) ->
formatter -> ('b, formatter, unit, 'a) format4 -> 'b
fprintf
above, but instead of returning immediately,
passes the formatter to its first argument at the end of printing.val ikfprintf : (formatter -> 'a) ->
formatter -> ('b, formatter, unit, 'a) format4 -> 'b
kfprintf
above, but does not print anything.
Useful to ignore some material when conditionally printing.val ksprintf : (string -> 'a) -> ('b, unit, string, 'a) format4 -> 'b
sprintf
above, but instead of returning the string,
passes it to the first argument.val kasprintf : (string -> 'a) -> ('b, formatter, unit, 'a) format4 -> 'b
asprintf
above, but instead of returning the string,
passes it to the first argument.val bprintf : Buffer.t -> ('a, formatter, unit) format -> 'a
If you need to print to some buffer b
, you must first define a
formatter writing to b
, using let to_b = formatter_of_buffer b
; then
use regular calls to Format.fprintf
on formatter to_b
.
val kprintf : (string -> 'a) -> ('b, unit, string, 'a) format4 -> 'b
ksprintf
.val set_all_formatter_output_functions : out:(string -> int -> int -> unit) ->
flush:(unit -> unit) ->
newline:(unit -> unit) -> spaces:(int -> unit) -> unit
set_formatter_out_functions
.val get_all_formatter_output_functions : unit ->
(string -> int -> int -> unit) * (unit -> unit) * (unit -> unit) *
(int -> unit)
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
pp_set_formatter_out_functions
.val pp_get_all_formatter_output_functions : formatter ->
unit ->
(string -> int -> int -> unit) * (unit -> unit) * (unit -> unit) *
(int -> unit)
pp_get_formatter_out_functions
.val pp_open_tbox : formatter -> unit -> unit
val pp_close_tbox : formatter -> unit -> unit
val pp_print_tbreak : formatter -> int -> int -> unit
val pp_set_tab : formatter -> unit -> unit
val pp_print_tab : formatter -> unit -> unit
val open_tbox : unit -> unit
val close_tbox : unit -> unit
val print_tbreak : int -> int -> unit
val set_tab : unit -> unit
val print_tab : unit -> unit