Re: case-insensitive string comparison

[Eli Zaretskii <eliz@gnu.org>]

> From: Roland Winkler <winkler@gnu.org>
> Cc: monnier@iro.umontreal.ca,  emacs-devel@gnu.org
> Date: Wed, 20 Jul 2022 13:10:35 -0500
> 
> On Wed, Jul 20 2022, Eli Zaretskii wrote:
> >> Even mentioning the difficulties could be useful here.
> >
> > I'm not sure I agree.  To describe all the important aspects of this
> > would take too long, and it isn't the job of our manual to document
> > this stuff.  Read this if you want to know:
> >
> >   https://unicode.org/reports/tr10/
> 
> A footnote pointing the interested reader to this report could already
> be useful.

I'll see if we have a good place for that.

> > Not the users should build the case table, BBDB (or whatever Lisp
> > program that needs the comparison) should.  It's not that hard,
> > really: if you only need ASCII, use ascii-case-table, otherwise copy
> > the standard case-table and modify it to make sure I downcases to i
> > and similarly with a few other exceptional letters.
> 
> I am not sure it would be possible to predict how a default case table
> for BBDB should differ from the standard case table.  BBDB might be the
> only package of a user that accumulates strings that go beyond what
> otherwise a user is dealing with regularly.  If there is a sensible
> "BBDB default case table" I'd hope that this is the standard case table.

Maybe BBDB can just use the standard case table, I don't know.  You
should be the judge of that: if your users don't care with I not being
equal to i case-insensitively, when the language-environment happens
to be Turkish, then you shouldn't worry about that.

> Or if not: can you suggest an emacs package that I can look into as a
> source of inspiration?

I'm not aware of any (which is not to say there isn't any, just that I
don't know).