bug#19878: 24.4; Syntax class [:alpha:] wrongly matches the Indian digits ۱۲۳۴۵۶۷۸۹۰ as letter

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 17 Feb 2015 18:13:05 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: mohammad.mahmoudi@gmail.com, 19878@debbugs.gnu.org
> 
> > From: Andreas Politz <politza@hochschule-trier.de>
> > Date: Sun, 15 Feb 2015 21:16:13 +0100
> > Cc: 19878@debbugs.gnu.org
> > 
> > 
> > I think this is supposed to be:
> > 
> > ,----[ (info "(elisp) Char Classes") ]
> > | `[:alpha:]'
> > |      This matches any letter.  (At present, for multibyte characters, it
> > |      matches anything that has word syntax.)
> > `----
> 
> Indeed, which doesn't sound very nice.
> 
> Does someone object to the changes below (to be installed on master)?
> They make [:alpha:] and [:alnum:] closer to the Unicode
> recommendations in UTS #18, although we are still very far from
> supporting even Level 1 of conformance.  But these two seem like
> low-hanging fruit to me.
> 
> The modified definitions of these two sets are not 100% compatible
> with the old ones for the multibyte characters.  However, if it turns
> out that some code used these to get word-constituent characters,
> those places should simply be changed to use \sw instead.

No further comments, so I pushed the changes as commit 1a50945 on the
master branch, and I'm marking this bug closed.

> Also, does someone see any potential problem to make [:digit:] be a
> superset of the current ASCII-only set, to match UTS #18 as well?  The
> comment in regex.c says it is "only used for single-byte characters",
> but it isn't clear to me whether this is a requirement, i.e. there's
> some code in Emacs that relies on that, or just a statement of facts.

I'd still like to hear an answer and/or opinions about this.  If I
hear no comments, I will look into making a similar change to
[:digit:] soon.