NAME¶
GraphViz::Regex - Visualise a regular expression
SYNOPSIS¶
use GraphViz::Regex;
my $regex = '(([abcd0-9])|(foo))';
my $graph = GraphViz::Regex->new($regex);
print $graph->as_png;
DESCRIPTION¶
This module attempts to visualise a Perl regular expression. Understanding
regular expressions is tricky at the best of times, and regexess almost always
evolve in ways unforseen at the start. This module aims to visualise a regex
as a graph in order to make the structure clear and aid in understanding the
regex.
The graph visualises how the Perl regular expression engine attempts to match
the regex. Simple text matches or character classes are represented
by.box-shaped nodes. Alternations are represented by a diamond-shaped node
which points to the alternations. Repetitions are represented by self-edges
with a label of the repetition type (the nodes being repeated are pointed to
be a full edge, a dotted edge points to what to match after the repetition).
Matched patterns (such as $1, $2, etc.) are represented by a 'START $1' ..
'END $1' node pair.
This uses the GraphViz module to draw the graph.
METHODS¶
new¶
This is the constructor. It takes one mandatory argument, which is a string of
the regular expression to be visualised. A GraphViz object is returned.
my $graph = GraphViz::Regex->new($regex);
as_*¶
The regex can be visualised in a number of different graphical formats. Methods
include as_ps, as_hpgl, as_pcl, as_mif, as_pic, as_gd, as_gd2, as_gif,
as_jpeg, as_png, as_wbmp, as_ismap, as_imap, as_vrml, as_vtx, as_mp, as_fig,
as_svg. See the GraphViz documentation for more information. The two most
common methods are:
# Print out a PNG-format file
print $g->as_png;
# Print out a PostScript-format file
print $g->as_ps;
BUGS¶
Note that this module relies on debugging information provided by Perl, and is
known to fail on at least two versions of Perl: 5.005_03 and 5.7.1. Sorry
about that - please use a more recent version of Perl if you want to use this
module.
AUTHOR¶
Leon Brocard <
acme@astray.com>
COPYRIGHT¶
Copyright (C) 2000-1, Leon Brocard
This module is free software; you can redistribute it or modify it under the
same terms as Perl itself.