From: Robert Klemme <shortcutter@...>
Date: 2007-03-17T23:45:04+09:00
Subject: Re: A couple of questions from a Ruby neophyte

On 17.03.2007 15:37, Phrogz wrote:
> On Mar 10, 1:34 am, "gga" <GGarram...@aol.com> wrote:
>> On 8 mar, 09:08, "planetthoughtful" <planetthought...@gmail.com>
> One question:
>> Ruby1.8's regexp engine is less powerful than Perl's or Python's as it
>> does not have backtracking, named groups or unicode (if you don't know
>> what that is or care, ruby1.8's regexp are perfect for you already).
> 
> If I understand the terminology correctly, the 1.8 regexp engine
> doesn't support lookbehind assertions (positive or negative), but it
> does support backtracking. Isn't backtracking what permits /.*bar/ to
> match "foobar"? Without backtracking, .* would match "foobar", and
> then the regexp would fail when it didn't find another "bar" after
> "foobar".

Yes.  Basically NFA regexp engines have to do backtracking, DFA's don't. 
  See "Mastering Regular Expressions" for details.

Kind regards

	robert