Re: On language-dependent defaults for character-folding

[Eli Zaretskii]

> Date: Sat, 13 Feb 2016 09:20:39 -0800 (PST)
> From: Drew Adams <address@hidden>
> Cc: address@hidden, address@hidden
> 
> > The implementation should really be on the C level, like the
> > case-folding support.  The current implementation isn't, and
> > therefore has several disadvantages some of which were already
> > pointed out (e.g., the regexp it uses that gets exposed in some
> > situations and causes users to be surprised).
> 
> I would like to see a list of the disadvantages laid out clearly.

They were mentioned in the discussions since this feature was designed
and till this day.  I'm sorry, but I have no time for searching and
summarizing them.  It isn't easier for me than for anyone else, and
doesn't require any specialized knowledge.

> In general, I prefer that things be implemented in Lisp.
> That leaves them far more open to Emacs users, and hence to
> imagination and enhancement - which can often help Emacs
> farther down the road.

Not in this case.  Search must be fast, it must support regular
expressions and complex character transformations, all of which cannot
be done well in Lisp, even if we expose buffer text to Lisp, something
we don't have today.

> Implementation in C makes great sense in some cases, but it
> would help to see the detailed arguments (cases).

These arguments were already given, you will find them in the
archives.

> The argument that a complex, not-user-friendly, under-the-covers
> regexp might sometimes get exposed to users is OK, but it is not
> really compelling (for me).  Some users, in some case, might well
> want to make use of such a regexp (e.g. tweaking it).

Users should tweak tables that tell Emacs how to fold characters, they
should not tweak the results of folding.  Like they do (if they do)
with case-tables today.