Re: Help with a grammar problem

On Thursday 03 September 2009 01:50:58 Damian Conway wrote:
> Hi Mike,
>
> > What I've tried amounts to this:
> >
> > chunk: /.*?/ delimiter_start command(s) delimiter_end /.*?/
>
> Unfortunately that won't work, because every regex in a PRD grammar is
> independent of the rest of the grammar, so even a minimal-matching .*?
> eats everything.

Ya, that's what I was suspecting.  In hind sight, I should have figured that; 
that's how I'd write it...

> Is there some reason you can't use something like:
>
>     my $parser = Parse::RecDescent->new($grammar);
>
>     $text =~ s{<DELIMITER> (.*?) </DELIMITER>}
>             { $parser->parse($1); q{} }gexs;

That's what I was doing, but it seems I misinterpreted my profiling results.  
I found from profiling that the function I use to create (once) and run the 
parser accounted for 80% of runtime.  

I assumed that since I only create the parser once (if !defined), creating the 
parser wasn't where the cost was.  So I decided that it must be due to 
actually running the parser, which might run several times during program 
execution.  My conclusion was that I needed to rewrite the grammar so that 
the parser would only run once.

It sounds like I may need to go back to the old algorithm and start tuning the 
grammar.

-- 

Take care and have fun,
Mike Diehl.