Re: Parse::Recdescent optional subrule commit

Making the subrule mandatory, while allowing it to match nothing solves the problem.

#!/usr/bin/env perl

use strict;
use warnings;
use feature qw( say );

use Parse::RecDescent qw( );

my $grammar = <<'__EOI__';

   myrule    : 'stuff' mysubrule
             | <error>
   mysubrule : 'ID' <commit> '[' ']'
             | <error?> <reject>
             |

__EOI__

my $parser = Parse::RecDescent->new($grammar)
   or die;

for my $text ("stuff ID something", "stuff something") {
   say "====================";
   say "$text";
   say "--------------------";
   say $parser->myrule($text) ? 'pass' : 'fail';
}
[download]

====================
stuff ID something
--------------------

       ERROR (line 1): Invalid mysubrule: Was expecting '[' but found
                       "something" instead

       ERROR (line 1): Invalid myrule: Was expecting mysubrule but fou
+nd "ID
                       something" instead
fail
====================
stuff something
--------------------
pass
[download]

Comment on Re: Parse::Recdescent optional subrule commit Select or Download Code

Replies are listed 'Best First'.
Re^2: Parse::Recdescent optional subrule commit by ikegami (Patriarch) on May 02, 2012 at 20:18 UTC
And below is how to do it with the optional subrule. It even provides better error messages. #!/usr/bin/env perl use strict; use warnings; use feature qw( say ); use Parse::RecDescent qw( ); my $grammar = <<'__EOI__'; myrule : <rulevar: local $failed = 1> myrule : 'stuff' mysubrule(?) <reject:$failed> mysubrule : 'ID' <commit> '[' ']' \| <error?> { $failed = 0; } <reject> __EOI__ my $parser = Parse::RecDescent->new($grammar) or die; for my $text ("stuff ID something", "stuff something") { say "===================="; say "$text"; say "--------------------"; say $parser->myrule($text) ? 'pass' : 'fail'; } [download] `==================== stuff ID something -------------------- ERROR (line 1): Invalid mysubrule: Was expecting '[' but found "something" instead fail ==================== stuff something -------------------- pass` [download]	[reply] [d/l] [select]
Re^3: Parse::Recdescent optional subrule commit by campugnatus (Initiate) on May 03, 2012 at 08:04 UTC
This is elegant and simple! Thank you!	[reply]