Re: getting latest $thisoffset

[Ron D. Smith]

> 
> Hi,
> To facilitate my error reporting, I'd like to know the largest that
> $thisoffset ever gets. For example, if I have some grammar with this rule:
> 
>   sentence: subject verb object
> 
> if it fails to parse an 'object', I'd like to get the $thisoffset as of
> the 'verb' which had been parsed, as if my rule was
> 
>   sentence: { RememberMax($thisoffset) } subject
>             { RememberMax($thisoffset) } verb
>             { RememberMax($thisoffset) } object
>             { RememberMax($thisoffset) }
> 
> Is there any way to access or automate this?
> 
> Thanks.

perl << 'END'
use Parse::RecDescent;

#$::RD_TRACE=50;
#$::RD_HINT=1;
#$::RD_CHECK=0;
$::RD_AUTOACTION = q { $item[1] };
my $grammar_all=q(
<autotree>
   sentence: { Somewhere::ResetMax();Somewhere::RememberMax($thisoffset) } 
subject
             { Somewhere::RememberMax($thisoffset) } verb
             { Somewhere::RememberMax($thisoffset) } object
             { Somewhere::RememberMax($thisoffset) }
             {$return=[$item[2],$item[4], $item[6]]}

object: ('book'|'car'|'computer')
verb: ('is'|'was'|'go'|'sat')
subject: ('i'|'you'|'them') 
);


my $parserRef = new Parse::RecDescent($grammar_all); 

$res=$parserRef->sentence('i is book');
print Somewhere::GetMax()." was the max.\n";
$res=$parserRef->sentence('i is bok');
print Somewhere::GetMax()." was the max.\n";
$res=$parserRef->sentence('he is foobar');
print Somewhere::GetMax()." was the max.\n";

package Somewhere;
my $max;
sub RememberMax {
    my $arg=shift;
    $max=$arg if ($arg>$max);
    1;
}

sub GetMax {
    $max
}

sub ResetMax {
    $max=-1;
}

'END'
--

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