Subject: bug#23833: 24.5; assoc-string with CASE-FOLD may fail

From: Noam Postavsky <[email-masked]>
Date: Thu, 23 Jun 2016 11:53:00 -0400

On Thu, Jun 23, 2016 at 11:11 AM, Eli Zaretskii <[email-masked]> wrote:
>> From: Noam Postavsky <[email-masked]>
>> Date: Thu, 23 Jun 2016 08:26:22 -0400
>> Cc: [email-masked]
>>
>> assoc-string uses compare-strings, which uses upcase to ignore case,
>> but upcase is not always the inverse of downcase:
>>
>> (upcase (downcase "Ǳ")) ;=> "ǲ"
>> ;; Or to put it another way
>> (= (upcase (downcase ?\u01F1)) ?\u01F2) ;=> t
>>
>> Same behaviour seen in emacs-25 and master
>
> Thanks.
>
> This is a documentation issue: both 'assoc-string' and
> 'compare-strings' had inaccuracies in their doc strings.  I fixed this
> on the emacs-25 branch, and I'm marking this bug done.

Would it not make more sense if upcase converted ǳ into Ǳ? According
to https://en.wikipedia.org/wiki/Dz_(digraph)#Unicode ǲ is the "title
case" form, not upper case form. Or is this something that depends on
locale?