NAME

       GraphViz::Parse::RecDescent - Visualise grammars

SYNOPSIS

         use GraphViz::Parse::RecDescent;

         # Either pass in the grammar
         my $graph = GraphViz::Parse::RecDescent->new($grammar);
         print $g->as_png;

         # or a Parse::RecDescent parser object
         my $graph = GraphViz::Parse::RecDescent->new($parser);
         print $g->as_ps;

DESCRIPTION

       This module makes it easy to visualise Parse::RecDescent grammars.  Writing
       Parse::RecDescent grammars is tricky at the best of times, and grammars almost always
       evolve in ways unforseen at the start. This module aims to visualise a grammar as a graph
       in order to make the structure clear and aid in understanding the grammar.

       Rules are represented as nodes, which have their name on the left of the node and their
       productions on the right of the node. The subrules present in the productions are
       represented by edges to the subrule nodes.

       Thus, every node (rule) should be connected to the graph - otherwise a rule is not part of
       the grammar.

       This uses the GraphViz module to draw the graph. Thanks to Damian Conway for the idea.

       Note that the Parse::RecDescent module should be installed.

METHODS

   new
       This is the constructor. It takes one mandatory argument, which can either be the grammar
       text or a Parse::RecDescent parser object of the grammar to be visualised. A GraphViz
       object is returned.

         # Either pass in the grammar
         my $graph = GraphViz::Parse::RecDescent->new($grammar);

         # or a Parse::RecDescent parser object
         my $graph = GraphViz::Parse::RecDescent->new($parser);

   as_*
       The grammar 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

       Translating the grammar to a graph is accomplished by peeking inside the internals of a
       parser object, which is a tad scary. A new version of Parse::RecDescent with different
       internals may break this module.

       At the moment, almost all Parse::RecDescent directives are supported. If you find one that
       has been missed - let me know!

       Unfortunately, alternations (such as the following) do not produce very pretty graphs, due
       to the fact that they are implicit (unamed) rules and are implemented by new long-named
       subrules.

         character: 'the' ( good | bad | ugly ) /dude/

       Hopefully Parse::FastDescent will make this all much easier.

AUTHOR

       Leon Brocard <acme@astray.com>

COPYRIGHT

       Copyright (C) 2001, Leon Brocard

       This module is free software; you can redistribute it or modify it under the same terms as
       Perl itself.