Re^2: Parse::RecDescent for simple syntax-directed translation


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Re^2: Parse::RecDescent for simple syntax-directed translation

by tomazos (Deacon)

on Jun 18, 2006 at 18:17 UTC ( [id://556134]=note: print w/replies, xml )

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in reply to Re: Parse::RecDescent for simple syntax-directed translation
in thread Parse::RecDescent for simple syntax-directed translation

Thanks for answering my question. The regex solution is cool.

I should have qualified my statement by saying that standard regular grammars cannot handle this sort of pattern, whereas Perl's regexes can do everything and anything.

In fact embedded actions within a Perl regex can do anything Perl can do - Therefore Perl regex's can do anything Perl can do. :)

I guess I can see from your use of Parse::RecDescent, Update: And from re-reading the very long manual last night, that the answer to my question is something like:


my $grammar = q{
   match : part(s) { print join('', @{$item[1]}) }

   part : AnB
   part : 'a'
   part : /[^a]+/

   AnB : 'a' AnB 'b' { 'c' . $item[2] . 'd' }
   AnB : 'ab' { 'cd' }
}
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-Andrew.

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Re^3: Parse::RecDescent for simple syntax-directed translation
by ikegami (Patriarch) on Jun 20, 2006 at 23:52 UTC

Close. Your grammar strips out all whitespace. Replace
match : part(s) { print join('', @{$item[1]}) }
with
match : <skip:''> part(s) { print join('', @{$item[2]}) }

A slight improvement is to replace
match : <skip:''> part(s) { print join('', @{$item[2]}) }
with
process : <skip:''> part(s) { join('', @{$item[2]}) }
so you can do
$filter = Parse::RecDescent->new($grammar);
print $filter->process('eeeeaaaabbbeeee');

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