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

[Drew Adams]

> > current situation with case folding, that you can't paste in
> > a search string with capital letters and search for it in a
> > case-independent way.
> 
> Yes, you can: Use M-c to explicitly choose whether to case-fold or not.

Your "Yes" is really an agreement that no, you cannot, but you can
at least override/cancel Emacs's DWIM behavior, by then using `M-c'
to explicitly turn case-folding back on.

That is, after you figure out that Emacs has turned the tables on
you (and there is no signal that it has - no message telling you
that it is now searching case-sensitively), you can insist that
it go back to the mode you had already chosen: case-insensitive.

And thank goodness Emacs does not remove this possibility of
overriding its second-guessing.

> > However, in the case of case folding, we solve that by downcasing
> > text when pasting it into search strings.  We could de-accent
> > strings too when pasting them.
> 
> Actually, the way we downcase it has problems.  E.g. Go to the
> beginning of this paragraph (i.e. before "Actually") and do:
> C-s C-w M-c and you end up searching for an exact (non-case-folded)
> match of "actually" rather than "Actually", so it won't even match the
> "Actually" from which you got it.

Yes.  And see my reply to RMS - if you paste text with an uppercase
letter while editing the search string using `M-e', case-folding is
still turned off automatically.

IOW, the automatic downcasing DWIM is used only when you use `C-M-y'
(or `C-w') to yank some text at point into the search string.  What
was said about automatic downcasing is not true for pasting in
general.  Which points to another possibility of use confusion
(inconsistency).