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Re: Moving kbd to subr.el

From: Lars Ingebrigtsen
Subject: Re: Moving kbd to subr.el
Date: Fri, 15 Oct 2021 13:26:30 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux)

Eli Zaretskii <eliz@gnu.org> writes:

> The code deals with character codepoints, not with their multibyte
> representation.  So UTF-8 or not doesn't seem relevant here.

Sorry; I mean "Unicode code points", not utf-8.

Eli Zaretskii <eliz@gnu.org> writes:

>> > >                   always (and (characterp ch)
>> > >                               (let ((ch2 (logand ch (lognot ?\M-\^@))))
>> > >                                 (and (>= ch2 0) (<= ch2 127))))))


> Actually, I have to disagree with the conclusion that this is a
> complicated way of saying
>   (<= 0 ch 127)
> That's because 'ch' can include modifier bits set, and the above code
> resets them before comparing against 127.

But `characterp' just checks that ch is smaller than 0x3FFFFF, and

(dotimes (ch #x3FFFFF)
  (unless (equal
           (and (characterp ch)
                (let ((ch2 (logand ch (lognot ?\M-\^@))))
                  (and (>= ch2 0) (<= ch2 127))))
           (<= 0 ch 127))
    (error "%s" ch)))

shows no difference between the two tests in that range.  So perhaps the
logic it's trying to get at just doesn't work, or we have other problems

And note:

(characterp ?\M-\^@)
=> nil

It's hard to say, but I think the code wants to allow returning "\M-s"
as a string, but it doesn't:

(edmacro-parse-keys "M-s")
=> [134217843]

So the code today is equivalent to (<= 0 ch 127), but that's probably
because it's buggy -- perhaps always has been, but perhaps it's because
we've changed how characters are represented.

(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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