NAME

GraphViz::Regex_YAPE - Visualise a regular expression

SYNOPSIS

use GraphViz::Regex_YAPE;

my $regex = '(([abcd0-9])|(foo))';

my $graph = GraphViz::Regex_YAPE->new($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 'Capture start' .. 'Capture end' node pair.

This module is an alternative to the GraphViz::Regex module which uses the YAPE::Regex module by Jeff Pinyan. It is probably slightly more portable than GraphViz::Regex, which uses the Perl debugger. Which do you prefer?

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 $graph = GraphViz::Regex_YAPE->new($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;

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.