RE: lax matching is not a great default behavior

[Drew Adams <drew.adams@oracle.com>]

> > > > Agreed.  And neither is it folding of diacriticals, because
> > > > there are also ad hoc foldings (e.g., quote marks).  And there
> > > > will likely be more to come.  It is, in fact, a hodge podge of
> > > > foldings - pretty much all of the various char foldings provided
> > > > by Emacs so far, except for letter case.
> > >
> > > Actually, it's not a hodge-podge at all.  Barring any user-level
> > > customizations, it can be formally defined (and has been defined
> > > elsewhere) what is and what isn't folded.
> >
> > Whether it is formally defined or not does not answer the
> > question about the name to use for Emacs users.
> 
> "Character folding" is the accepted terminology for this, we didn't
> invent it.  Likewise "character sequence equivalence".

I've already agreed (from the beginning) that "character
folding" is the right term for Emacs to use.  And that
speaking of character equivalences is also appropriate.

(There has been some talk of adding multi-character string
equivalences, but even if we match strings instead of just
chars, speaking of "character foldings" makes sense to me.)

I mentioned "ad hoc" character equivalences because I didn't
think that the quotation-mark equivalences we've added are
included in any of the Unicode equivalences (whether
"canonically equivalent" or "compatible").

Are you saying that they are so included?  And that the
equivalences that Emacs will use are _all_ of those defined
by Unicode?

If not, then I'd still say that Emacs does character folding,
but _some_ character folding; a certain kind of character
folding.  And AFAIK we don't have a specific term that
characterizes just the folding we do.  (Which is OK.)

And we _will_ have "user-level customizations" - user-defined
equivalence classes, in the future (I hope).  IOW, more ad hoc
foldings to come.  We will have our - Emacs's - character
folding, which won't map one-to-one onto Unicode equivalences.
(Unless I'm mistaken about the quote-mark equivalences, this
is already the case.)

But again, "character folding" is the best term I've heard
mentioned for what Emacs does.  We need not use it always in
exactly the same sense as Unicode.

> We are not changing the default.  We introduced a new feature, and
> this discussion is whether that feature should or shouldn't be turned
> on by default.  There's no previous default here.

Hm.  That sounds close to gobbledygook, to me.  Turned on by
default would mean a changed default behavior: the behavior
you get without doing anything (toggling, customizing, coding)
would be different, new, never seen before by Emacs users.

There was no such _choice_ before, so the "default" matching
behavior until Emacs 25 was the only matching behavior, but if
that's your point, in claiming that turning this new behavior
on from the outset would not be changing the default behavior,
then I'd say that being that pedantic is, well, a bit silly.

Yes, users will now have a choice.  Should they need to do
something (e.g. toggle) to get the new behavior or not?
That's the question.  You say no; I think yes, a priori -
unless there are some good reasons otherwise.

> We have enough time to decide about the default for the release.
> Hopefully, we will have more data then than we have now, and the
> decision will be more informed one.

Agreed.  And _then_ we can entertain reasons to change the
"default" (initial) behavior.