NAME

Pegex::Regex - Use Pegex Like a Regex

SYNOPSIS

{
    # Turn on Pegex regular expressions in lexical scope.
    use Pegex::Regex;
    my $grammar = qr{$grammar_text}x;
    $text =~ $grammar;
    my $data = \%/;

    # Turn off Pegex in this scope.
    no Pegex::Regex;
}

DESCRIPTION

This is a trivial sugar module that lets you use Pegex parser grammars like regular expressions, if you're into that kind of thing.

This is basically a clone of Damian Conway's Regexp::Grammars module API. You put a grammar into a qr{...}x and apply it the input string you want to parse. If the parse is successful, you get a data structure of the content in %/.

IMHO, building a recursive decscent parser entirely inside of a regular expression, is not the clearest way to code. But, of course, TMTOWTDI. :)

TMTOWTDI

Here's a Pegex::Regex code snippet:

use Pegex::Regex;
$text =~ qr{path/to/grammar_file.pgx};
print $/{foo};

And the equivalent Pegex code:

use Pegex;
my $data = pegex('path/to/grammar_file.pgx')->parse($text);
print $data->{foo};

And the more explicit Pegex solution:

use Pegex::Grammar;
my $grammar = Pegex::Grammar->new(
    text => 'path/to/grammar_file.pgx',
);
my $data = $grammar->parse($input);
print $data->{foo};

And even more explicit yet:

use Pegex::Grammar;
use Pegex::Compiler;
use Pegex::Parser;
use Pegex::Receiver;
use Pegex::Input;
my $parser = Pegex::Grammar->new(
    grammar => Pegex::Grammar->new(
        tree => Pegex::Compile->compile(
            Pegex::Input->new(
                file => 'path/to/grammar_file.pgx',
            )
        )->tree,
    ),
    parser => 'Pegex::Parser',
    receiver => 'Pegex::Receiver',
);
$parser->parse(Pegex::Input->new(string => $input));
print $parser->receiver->data->{foo};

In the last example there are 5 components/classes, all of which you can subclass to make your perfect parser.

Pegex::Regex is just a gateway drug. :)

INPUT OPTIONS

There are different ways to input a grammar into a Pegex::Regex:

qr{
    grammar: <as> <text>
}x;
qr{$grammar_in_a_variable}x;
qr{path/to/grammar-file.pgx};

Make sure to use the x modifier if you are specifying the grammar as a literal string or in a variable.

This gateway drug, er, module, technically should not even work.

It turns your "grammar inside a regexp" into a Pegex::Grammar using qr{} overloading, and then turns your regexp itself into a shim that calls the parse method for you. This is highly magical and technically makes a reentrant call to the regex engine, which is not supported yet. Use at your own risk.

Better yet, do yourself a favor and learn how to use the Pegex toolset without this ::Regex sugar. :-)

SEE ALSO

• Pegex

• Regexp::Grammars

AUTHOR

Ingy döt Net <ingy@cpan.org>

COPYRIGHT AND LICENSE

Copyright (c) 2011. Ingy döt Net.

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

See http://www.perl.com/perl/misc/Artistic.html

cpanm Pegex

perl -MCPAN -e shell
install Pegex