Re: Single quotes in Info

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 28 Jan 2015 22:01:09 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: emacs-devel@gnu.org
> 
> > I'm not at all sure we should compare a and á equal.  It's an
> > additional feature anyway.
> 
> I get the impression that you are talking only about a built-in
> (more or less hard-coded, predefined) set of equivalence classes
> of chars, whatever that set might be defined as.

We certainly should have predefined equivalence support based on the
Unicode Standard's recommendations.  That is the state of the art
these days, and any respectable text editor should include such
support.

> Is that right, or would users be able to define the equivalence
> classes you are thinking of?

We should first provide users with a set of sensible optional
behaviors that they are likely to expect in various situations.  Each
option will invoke a certain predefined behavior, such as whether or
not equivalence classes are at all considered, whether or not a and á
compare equal, etc.  There are important use cases for each one of
those, exactly like there important use cases for both case-sensitive
and case-insensitive search.

Once we have that in place, we can add user-defined additions.  I
expect them to be relatively minor and mostly mode-specific, such as
the special treatment of quotes and other special characters in Info
buffers.  Why minor? because Unicode already thought out and defined
almost any imaginable feature in this regard, so chances that some
user might need something in addition are small.

Mode-specific additions could be just alists that map characters or
strings to their equivalents.  Since I don't expect those to become
large, there's no need for anything fancier, IMO.

> If they would not then a separate but desirable (IMO) feature
> would be for users to be able to easily define their own such
> equivalence classes.

I wouldn't call them equivalence classes.  Users are not expected to
be experts in Unicode features, its various data tables, and their
implementation in Emacs.  We should instead provide easy-to-customize
option variables to select out of an array of predefined features
based on Unicode tables we already have.  User additions should be
some simple data structure that don't require any special expertise.