Re: char equivalence classes in search - why not symmetric?

[Stephen J. Turnbull]

Jean-Christophe Helary writes:

 > Let's just put flags that trigger case/diacritic matching, they
 > could be on in default emacs, but they should be somewhere.

They're already there.  The discussion here is entirely about the DWIM
UI of isearch that allows requesting strict matching by having at
least one uppercase or accented character, even though lax mode is
enabled.

Drew prefers a UI that enables/disables strict mode using a special
isearch command bound to a key.  That would be plausible, if the DWIM
UI for case fold search in isearch weren't 3 decades old.  But the
DWIM UI *is* 3 decades old, and successful.  Drew disputes that, but
in the 25 years I've followed Emacs development this is the first time
I've seen anybody complain about the DWIM-ish case folding feature.
Note that incremental case-folded search (usually with no escape for
strict matching!) has been widely adopted in web and file browsers.

I'm +1 on generalizing this UI to "diacritic folding" in isearch.

The other question is that of Ulrich Müller, who points out that it's
natural for him to type his name correctly, but he'd like to laxly
match Mueller and Muller, too.[1]  It's a valid use case, obviously,
but based on an analogy to experience with DWIMish case-folding in
Emacs, I believe most users will quickly adjust to typing "muller"
when they want a poor man's version of full "orthographic
equivalence".  Individuals may not, but I believe the great majority
will, since I'm sure it's anatomically easier to type "muller" than
"Müller", even on a German keyboard.


Footnotes: 
[1]  Drew also argues this point, but from an abstract insistence on
"symmetry", which doesn't really exist here for representational,
anatomical, psychological reasons, and let's not forget personal
historical reasons like "Müller is my name".