GraphViz::Parse::RecDeUsertContributed Perl DocuGraphViz::Parse::RecDescent(3)NAMEGraphViz::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.
perl v5.14.3 2012-11-09 GraphViz::Parse::RecDescent(3)
