bug#17130: 24.4.50; Deficient Unicode case folding

[Eli Zaretskii]

> From: nbtrap@nbtrap.com
> Cc: 17130@debbugs.gnu.org
> Date: Fri, 28 Mar 2014 15:31:09 -0400
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> M-: (compare-strings "σ" nil nil "ς" nil nil t)
> >> 
> >> ==> -1  ;; should be t
> >
> > No, because these characters are not a case pair.
> 
> They're not a case pair in Emacs, but they should compare equally under
> Unicode case folding.

Emacs doesn't currently support that.

> >> Can someone that knows a thing about Unicode and emacs case tables speak
> >> to whether the latter could suffice for implementing full Unicode case
> >> folding?
> >
> > What is "full Unicode case folding"?
> 
> Somthing that implements this:
> http://www.unicode.org/Public/UNIDATA/CaseFolding.txt
> 
> And perhaps more.  I don't know, but someone on this list probably does.
> 
> If you look about a third of the way down, there's a line saying that
> U+03C2 (ς) should fold into U+03C3 (σ).

Patches are welcome to import those tables into Emacs, and make case
folding support them.