Re: [Chicken-hackers] [PATCH] Irregex bugfix and update to 0.9.1

[Peter Bex]

On Tue, Nov 27, 2012 at 08:46:22PM +0100, Peter Bex wrote:
> Hi all,
> 
> Prompted by some discussion and a bogus patch by me, Alex came up with
> a very simple but effective fix for ticket #686.  We've made a new
> bugfix release for irregex, 0.9.1, so here's a patch to bring Chicken
> up-to-date with upstream.
> 
> The fix is pretty simple; if you know the regex is a "searcher" (one
> that starts with 'bos, ie the beginning of a string), don't loop in
> the fold procedure because it can't possibly match anymore.  This should
> also improve performance for such regex matches that can be short-cut
> like this.

This fix turns out to be incomplete.  A regex like (or (seq bos "a") "b")
is not a searcher (because a regex is a searcher only when all its
components are searchers), and will still do the wrong thing when used
with irregex-replace/all.

However, this patch can still be applied as it has been pushed to
upstream and should indeed be a performance improvement in all
cases, I think, and it correctly fixes the simpler cases.

A more complete patch will hopefully be posted later.

Cheers,
Peter
-- 
http://sjamaan.ath.cx
--
"The process of preparing programs for a digital computer
 is especially attractive, not only because it can be economically
 and scientifically rewarding, but also because it can be an aesthetic
 experience much like composing poetry or music."
                                                        -- Donald Knuth