From: "Andrew S. Townley" <ast@...>
Date: 2009-04-14T03:20:40+09:00
Subject: Re: Using ruby for generic language parsing (or any	language-specific parsing libraries out there?)

On Tue, 2009-04-14 at 02:17 +0900, Aaron Patterson wrote:
> On Tue, Apr 14, 2009 at 01:29:51AM +0900, Andrew S. Townley wrote:

[what I was looking for snipped]

> > In the past, I've written parsers with Lex/Yacc, and I did do some work
> > a couple of years ago with rex & racc, but for anything as complex as
> > the above, I think rex/racc would be a) too time consuming/error prone
> > (I found it incredibly difficult to debug and diagnose problems and
> > generate reasonable error messages) and b) surely re-inventing the wheel
> > for the nth time, where n > 10,000,000,000. :)
> 
> I've been using rex and racc for quite a while, and I'm pretty happy
> with both of them.  I've found racc to be quite good in combination with
> existing Yacc grammars.  I've written a pure ruby JavaScript parser[1]
> and CSS parser[2][3] using racc.  I started on a C parser, but decided it
> wasn't worth my time because I didn't want to deal with preprocessor
> statements and we already have CAST[4].  Other non-trivial racc usage is
> Ryan Davis's ruby parser[5] which is a ruby parser written with racc.

Wow.  Thanks for all the examples!  I'll have to poke through your
rex/racc usage to see what I was doing wrong trying to get decent error
handling.  I finally just gave up and hand-coded a parser for what I was
trying to do.  Of course, I guess I should've mentioned that my lex/yacc
days were a looooong time ago, and I'm a bit rusty with hard-core
parsing & compiler writing (even though I used to think it was cool and
even, dare I say it, even kinda fun).  That might've had something to do
with my difficulties as well. :)

The CAST example looks *very* interesting.

> > I looked a bit at rparsec and treetop, but before I go down this path, I
> > was hoping to tap some of the community's collective wisdom for pointers
> > to similar initiatives.
> 
> Treetop looks neat.  Last time I looked at it though, it couldn't do
> error recovery in grammars similar to the error token in Yacc.  That may
> have changed since I looked at it last.
> 
> [1] http://github.com/tenderlove/rkelly/tree/master
> [2] http://github.com/tenderlove/csspool/tree/master
> [3] http://tinyurl.com/dkn8y4
> [4] http://cast.rubyforge.org/
> [5] http://rubyforge.org/forum/forum.php?forum_id=29842

The main things that concern me about them is that I won't be able to
easily adapt existing grammars for lex/yacc-based parsers (or even
ANTLR).  If I do have to go my own way, I don't want to write more than
I must.

Cheers for the info.

ast
-- 
Andrew S. Townley <ast@atownley.org>
http://atownley.org