Re: regex and case-fold-search problem

["Stefan Monnier" <monnier+gnu/emacs@rum.cs.yale.edu>]

> In article <5x8z2pj13t.fsf@kfs2.cua.dk>, storm@cua.dk (Kim F. Storm) writes:
> > IMO, it is wrong to handle case-fold-search for regexp ranges by
> > trying to modify the interpretation of the regex range.
> 
> > Instead, the regex matcher should try to upcase and lowercase each
> > character in the string and see if either of these caracters are
> > within the given range.
> 
> I also reached to that idea.  It makes regexp compiling
> simpler and faster but makes regexp matching a little bit
> slower.  I don't know if that slowerness is tolerable or
> not, but it's worth trying.

Two things:

- Neither `upper(lower(x)) = x' nor `lower(upper(x)) = x' are guaranteed.
- The regexp matcher right now only has access to one of the two tables
  (I believe it's the `lower' but I'm not even sure) and so two chars
  are deemed to match if translate(a) = translate(b).

The first might be a non-issue, I don't know.
The second is more serious because that means that if we want to use
`upper' we'll need to somehow pass that table as well, which requires
changing the interface to the reg-matching functions.


	Stefan