Re: Moving kbd to subr.el

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Eli Zaretskii <eliz@gnu.org>,  emacs-devel@gnu.org
> Date: Fri, 15 Oct 2021 12:28:08 +0200
> 
> Stefan Kangas <stefankangas@gmail.com> writes:
> 
> > OK, so looking even closer at this to develop test cases for the above,
> > in the original code we have this convoluted mess:
> >
> > (if (and (not need-vector)
> >          (cl-loop for ch across res
> >                   always (and (characterp ch)
> >                               (let ((ch2 (logand ch (lognot ?\M-\^@))))
> >                                 (and (>= ch2 0) (<= ch2 127))))))
> >     (concat (cl-loop for ch across res
> >                      collect (if (= (logand ch ?\M-\^@) 0)
> >                                  ch (+ ch 128))))
> >   res)
> 
> Yeah, my eyes glazed over when reading that code the first few times.
> :-) 
> 
> > But that is equivalent to:
> >
> >     (<= 0 ch 127)
> 
> I think...  you're totally right.  It looks like a very convoluted way
> to write (<= 0 ch 127).

I don't read CL-ish very well, so I cannot help you here.  (Read: I
have no idea what this code does.)

> But perhaps there's historical reasons for the code being that way?  In
> the olden days, Emacs didn't use utf-8 as the character representation,
> so perhaps it made sense back then?

The code deals with character codepoints, not with their multibyte
representation.  So UTF-8 or not doesn't seem relevant here.  It seems
to all be about character codes with modifier bits set.