Re: Random Tips on Parse::RecDescent

[davistar]

hsm,
Thanks for the excellent tips on PRD! I'm trying to use tip #16 for C-like multiline comments '/*' and '*/'.
I don't quite understand your syntax for the following production:

xcomment:
        <skip: qr/[ \t]*/> newline(0..) '<!--'
        {
            ($text,$return) = main::parse_delimited($text,'<!--','-
++->');
             $return = ['xcomment',$return];
        }

I translated your xcomment production into the following production:

comment:
        <skip: qr/[ \t]*/> newline(0..) '/*'
        {
            ($text,$return) = main::parse_delimited($text,'/*','*/');
             $return = ['comment',$return];
        }

My question is I don't understand the newline(0..) part I must missing something obvious. I had errors if I used newline(0..) and main::parse_delimited so I removed newline(0..) and changed main:: to $thisparser-> and ran the following test with no compile errors but it fails to match the comment production. What am I missing? Any help debugging would be appreciated!

#!/usr/bin/perl -w
use strict;
use Parse::RecDescent;
use Text::DelimMatch;

$::RD_ERRORS = 1;
$::RD_WARN = 1;
$::RD_HINT = 1;
$::RD_TRACE = 1;

my $grammar = q{
{
   sub parse_delimited {
        my $text       = shift;
        my $startdelim = shift;
        my $enddelim   = shift;

        my $mc = new Text::DelimMatch( $startdelim, $enddelim );
        my ( $p, $m, $r ) = $mc->match( $text );

        if ($p) {
            $text = $p;
        }
        else {
            $text = "";
        }
        $text .= $r if ($r);
        $m =~ s/^$startdelim//;
        $m =~ s/$enddelim$//;
        return $text, $m;
    }
}
file: line(s) eofile { use Data::Dumper 'Dumper'; print Dumper @item}

line:
    comment
    | <error>

eofile: /^\Z/

comment:
        <skip: qr/[ \t]*/> '/*'
        {
            ($text,$return) = $thisparser->parse_delimited($text, '/*'
+, '*/');
             $return = ['comment',$return];
        }

};

my $parser = new Parse::RecDescent($grammar) or die "Bad grammar!\n";

while (<DATA>)
{
    chomp;
    print "$_...\n";
    defined($parser->file($_)) or print "Bad text!\n";
}

__DATA__
/*Hello
World
*/

I also get the following errors in the trace which are disconcerting but I don't think it's causing the problem:

Argument "/*" isn't numeric in addition (+) at C:/Perl/site/lib/Parse/
+RecDescent.pm line 2783, <DATA> line 1.
Use of uninitialized value in substitution (s///) at (eval 15)[C:/Perl
+/site/lib/Parse/RecDescent.pm:2618] line 22, <DATA> line 1.
Use of uninitialized value in concatenation (.) or string at (eval 15)
+[C:/Perl/site/lib/Parse/RecDescent.pm:2618] line 23, <DATA> line 1.
Use of uninitialized value in substitution (s///) at (eval 15)[C:/Perl
+/site/lib/Parse/RecDescent.pm:2618] line 23, <DATA> line 1.
Use of uninitialized value in substitution (s///) at (eval 15)[C:/Perl
+/site/lib/Parse/RecDescent.pm:2618] line 23, <DATA> line 1.