From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2002-09-24T05:39:23+09:00
Subject: Re: Lexing ... (was: Re: Regexp: How to Find Legitimate Tokens?)

In article <5.1.0.14.2.20020923123544.04fa7ee8@zcard04k.ca.nortel.com>,
Mark Probert  <probertm@nortelnetworks.com> wrote:
>At 11:44 PM 9/23/2002 +0900, Bill wrote:
>
>>[snip]
>>4) Are tools such as lex and yacc more powerful than Ruby in terms of
>>their lexing and parsing capabilities?  Without regard to efficiency, is
>>to use Ruby as easy as to use lex?  Is to use Ruby as easy as to use
>>yacc?  (Probably no, such as shown by the discussion on a parser tool in
>>Ruby?)
>
>One data point.
>
>Given the recent discussion on lexer/parsers for Ruby, I thought that I
>would do something I have been meaning to do for a while, port Coco/R to
>ruby.
>
>For those who don't know, Coco/R is an LL(1) recursive decent scanner/parser
>that basically takes an attributed EBNF as its input and generates the
>scanner, parser and a driver.  The things that I like about Coco/R is that
>the attributed grammar is easy to understand and everything is in one place
>(no separate lex and yacc files) and that it is very fast.
>
>So, I have taken the C/C++ source and started the convert-to-ruby process.
>I have the table-driven scanner done and I have to say that ruby is -very-
>powerful at doing this stuff.  Given that this is a first-pass, the code
>is a little ugly and not optimised in -any- way, but it performs pretty
>well.  The scanner is around 500 lines of commented code.  I expect that
>to drop.  And I have found it easier to write than lex code.
>
>Now on to the parser!  Then no more yacc-ing ...
>

Cool.  I also don't like having a seperate lexer and parse (like using lex 
and yacc) so this sounds interesting.  

Can we take a look at what you've got so far?

Phil