Re: Cannot get Marpa::R2 to prioritise one rule over another

Hello J.

UPDATE I probably missed your point.. now I see the IP is never reachead but always treated as if it was and hostname. I'll think a bit more about it..

The problem seems to be fixed if you put NAME ~ [\D]+ but you will fail again with a hostname like 42.perl.org Perhaps a more strict rule definition is needed to tell difference from ip and hostname.

original reply My help can be very limited because I still do not understand Marpa::R2 and I'm just moving my first, baby steps. I dont understand the rank nor the show_progress part (atm). So I reduced the example to something I know (removing the colors).

Is not the hostname coming from your :default ::= action => [name,values] ? This is what proposed in the synopsis but I find it a bit misleading.

If you see A dice roller system with Marpa::R2 and its prequel First steps with Marpa::R2 and BNF you will see an anonymous hash is used and is populated during the parsing phase. Maybe you can use a pattern like this (then you can check the validity of an IP or of a valid hostname in distinct part of the code).

I ended with the following code that seems to produce the expected result

#!/usr/bin/env perl
use warnings;
use strict;

use Data::Dumper;
use Marpa::R2;

my $rules = <<'END_OF_GRAMMAR';
    lexeme default  = latm => 1
    
    :default        ::= action => [values]
    <entry>         ::= <op> (SP) <hostaddr4> 
    <op>            ::= 'add' | 'remove'
    
    <ipv4>          ::= NUMBER ('.') NUMBER ('.') NUMBER ('.') NUMBER
    <hostname>      ::= NAME
    
    <hostaddr4>     ::= <ipv4> | <hostname> 
    
    SP              ~ [\s]+    
    NAME            ~ [\S]+
    NUMBER          ~ [\d]+
END_OF_GRAMMAR

my $input = <<'END_OF_INPUT';
add 192.0.2.1
add www.example.org
remove 192.0.2.2
END_OF_INPUT

my $grammar = Marpa::R2::Scanless::G->new({source => \$rules});

for (split /^/m, $input) {
    chomp;
    if (length $_) {
        print "\nPARSING: $_\n";
        
        my $recce = Marpa::R2::Scanless::R->new({
            grammar => $grammar, 
        });
        
        my $value_ref = $grammar->parse( \$_);
        print Dumper $$value_ref;
    }
}

__OUTPUT__

PARSING: add 192.0.2.1
$VAR1 = [
          [
            'add'
          ],
          [
            [
              '192.0.2.1'
            ]
          ]
        ];

PARSING: add www.example.org
$VAR1 = [
          [
            'add'
          ],
          [
            [
              'www.example.org'
            ]
          ]
        ];

PARSING: remove 192.0.2.2
$VAR1 = [
          [
            'remove'
          ],
          [
            [
              '192.0.2.2'
            ]
          ]
        ];
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Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

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