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Re: how to use parsing expressing grammar


From: W Dan Meyer
Subject: Re: how to use parsing expressing grammar
Date: Tue, 03 Mar 2009 23:52:25 +0000
User-agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.0.90 (gnu/linux)

Xah Lee <address@hidden> writes:

> On Mar 3, 9:59 am, Mike Mattie <address@hidden> wrote:
>> On Tue, 03 Mar 2009 17:34:41 +0000
>>
>> Leo <address@hidden> wrote:
>> > On 2008-12-21 09:49 +0000, Helmut Eller wrote:
>> > >> I'm pretty sure if you create it, more and more people will join
>> > >> it. I'm very interested in PEG and think it is of critical
>> > >> importance.
>>
>> > > I'll try to set up project at savannah.
>>
>> > I have seen the project on
>> >http://savannah.nongnu.org/projects/emacs-peg. I wonder it might be a
>> > good idea to make a newsgroup on gmane to link to the mailing list. It
>> > will make more Emacs users subscribe to it.
>>
>> > Best wishes,
>>
>> I was working on a PEG/CFG parser 
>> compiler:http://www.emacswiki.org/cgi-bin/wiki/ParserCompiler
>>
>> I will be resuming the development soon. Please keep me in the loop on such 
>> efforts.

Are we talking about memoising PEG (e.g Packrat) in elisp?  There might
be more people interested.  I do realise that Emacs doesn't have decent
parsing facility and it makes it's regular expression based engine in
more complex areas useless (mentioned nested tags). Since it's automata
based you cannot go beyond simple patterns.  That means also that
everybody is reinventing a wheel with implanting all those recursive
decent parsers when it comes to analyse, pretty print, syntax highlight
of such modes like Haskell one.  Packrat parser is the best option out
there currently because it recognises much complex grammar then LALR(1),
and it has no ambiguities with expressing these grammars. Works well
also as a standalone combinator based solution rather then a parser
generator, plus it is lex-less e.g allow to recognise several different
languages in _one_go_ and one context without marking them explicitly!
cheers Dan W


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