bug#16731: 24.3.50; Latin small letter sharp s is not considered lower-case

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: andreas.roehler@easy-emacs.de,  16731@debbugs.gnu.org
> Date: Thu, 13 Feb 2014 13:10:02 -0500
> 
> >> Doesn't sound too bad.  But it does beg the question: why check
> >> (downcase (c) != c) at all, then?
> > Because it's faster,
> 
> Is it?  Both lookups look like CHAR_TABLE_REF to me.
> 
> > and for most characters will do the job.
> 
> But we'll check the unicode table at least for more than half the
> characters (i.e. for all the lowercase and non-case characters), so the
> fast path can't give us more than a factor of 2 speed up anyway, and the
> slow path is made slower by unnecessarily looking up the case table.
> 
> I guess what I mean is that without actual measurements it's not obvious
> at all that speed is a good justification.

What about custom buffer-local case tables?