Hi Jeffrey,
Unless I'm misreading what you are suggesting, that seems to give me the
same failure as in the original post as in the code below.
use Marpa::R2;
>
> my $dsl = <<'END_OF_DSL';
> :default ::= action => [name,values]
> lexeme default = latm => 1
>
> :start ::= matches
>
> matches ::= match+
> match ::= id | non_id
> id ::= identifier action => do_id
> non_id ::= other
>
> identifier ~ [\w]+
> other ~ [\W]+
> END_OF_DSL
>
>
>
> my $grammar = Marpa::R2::Scanless::G->new( { source => \$dsl } );
> my $recce = Marpa::R2::Scanless::R->new(
> { grammar => $grammar, semantics_package => 'CodeProcess' } );
>
> my $input = '#####abc##';
> my $length_read = $recce->read( \$input );
>
> my $value_ref = $recce->value;
> my $value = ${$value_ref};
>
>
> sub CodeProcess::do_id {
> my ($start, $end) = Marpa::R2::Context::location();
> print "location() is ($start, $end)\n";
>
> my ($span_beg, $span_end) = $recce->g1_location_to_span($start, $end -
> $start);
> print "g1_location_to_span is ($span_beg, $span_end)\n";
> print "literal is ".$recce->literal($span_beg, $span_end -
> $span_beg)."\n";
> print 'but $_[1] shows this id rule matched '.$_[1]."\n";
> }
>
> which incorrectly outputs
> location() is (1, 2)
> g1_location_to_span is (0, 5)
> literal is #####
> but $_[1] shows this id rule matched abc
>
> Fortunately, the more complicated solution from my previous post is
working, so I'm not blocked, but it seems clearly not to be "the right
approach," so definitely still interested in understanding what is wrong in
the above.
Thanks,
Mike
On Monday, July 30, 2018 at 11:27:44 AM UTC-5, Jeffrey Kegler wrote:
>
> I've been traveling so my apologies for the delay and my thanks to
> Jean-Damien for filling in.
>
> Also my apologies for the interface, which is not exactly a model of
> clarity.
>
> G1 locations are *fenceposts*, but they are also used to represent tokens
> in which case the G1 location *after* the symbol is its G1 location. So
> your return indicates <id> starts at G1 location 1 and ends at G1 location
> 2. It is *at* G1 location 2. Here's the writeup in the doc
> <https://metacpan.org/pod/distribution/Marpa-R2/pod/Scanless/R.pod#G1-locations>
> .
>
> The second issue is spans versus ranges. Marpa::R2::Context::location()
> returns the G1 start and end locations. g1_location_to_span() wants a G1
> *span*. So you want $recce->g1_location_to_span($end, $end-$start).
> (Warning: I have not testing this, it's from memory.)
>
> I hope this helps.
>
> On Sat, Jul 28, 2018 at 8:27 PM, Michael Spertus <spertus...@gmail.com
> <javascript:>> wrote:
>
>> I'm sure I'm doing something very dumb here, but I'm not able to find the
>> part of the input stream that was matched by my rule from the action. The
>> following code reports the section of the input stream before the match
>>
>> use Marpa::R2;
>>>
>>> my $dsl = <<'END_OF_DSL';
>>> :default ::= action => [name,values]
>>> lexeme default = latm => 1
>>>
>>> :start ::= matches
>>>
>>> matches ::= match+
>>> match ::= id | non_id
>>> id ::= identifier action => do_id
>>> non_id ::= other
>>>
>>> identifier ~ [\w]+
>>> other ~ [\W]+
>>> END_OF_DSL
>>>
>>>
>>>
>>> my $grammar = Marpa::R2::Scanless::G->new( { source => \$dsl } );
>>> my $recce = Marpa::R2::Scanless::R->new(
>>> { grammar => $grammar, semantics_package => 'CodeProcess' } );
>>>
>>> my $input = '#####abc##';
>>> my $length_read = $recce->read( \$input );
>>>
>>> my $value_ref = $recce->value;
>>> my $value = ${$value_ref};
>>>
>>>
>>> sub CodeProcess::do_id {
>>> my ($start, $end) = Marpa::R2::Context::location();
>>> print "location() is ($start, $end)\n";
>>>
>>> my ($span_beg, $span_end) = $recce->g1_location_to_span($start,
>>> $end);
>>> print "g1_location_to_span is ($span_beg, $span_end)\n";
>>> print "literal is ".$recce->literal($span_beg, $span_end)."\n";
>>> print 'but $_[1] shows this id rule matched '.$_[1]."\n";
>>> }
>>>
>>>
>> as shown by the following output
>>
>> mps@CPP:~$ perl marpa_test.pl
>>> location() is (1, 2)
>>> g1_location_to_span is (0, 5)
>>> literal is #####
>>> but $_[1] shows this id rule matched abc
>>>
>>
>> How would I display the section of input text that is matched by the id
>> rule? I know I can reconstruct it from the children, but my real parser has
>> much more complex rules for which it would be really helpful to just find
>> the range in the input matched by the rule (including its children).
>>
>> Thanks,
>>
>> Mike
>>
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>
>
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