Re: eight-bit char handling in emacs-unicode

[Kenichi Handa <handa@m17n.org>]

In article <jwvhe12emr3.fsf-monnier+emacs/devel@vor.iro.umontreal.ca>, Stefan Monnier <monnier@IRO.UMontreal.CA> writes:
>>  The basic problem is that we don't distinguish a character
>>  (code) and a number.  So, we introduce a character object

> That's one way to look at the problem.
> Another is to say that the problem is instead that we do not distinguish
> between arrays of chars and arrays of bytes.

I agree that it's possible to grasp the problem in that way,
but I'm not sure which is the better way.  Could you explain
WHY yours is better?

[...]
> In Emacs-21 we worked around the problem by arranging for "the
> eight-bit-char that encodes to 192" to be represented by the integer 192, so
> as to avoid having to choose.  But with unicode, the 128-255 zone cannot be
> dedicated to eight-bit-char since it's already used up for latin-1, so we
> have to face the problem more directly.

> The places where Emacs-21 still had to choose, we just used heursitics,
> so `concat' will sometimes return a unibyte string, and sometimes
> multibyte string.

> So I think your options 1-3 are better than 4.  BTW, your function
> `eight-bit-char' should be named `byte-to-char' instead.

> Which of 1 to 3 is the best is not clear, and maybe we can just live with
> `make-string-unibyte' and `make-string-multibyte'.

I think you mean string-make-unibyte/multibyte, but, for the
current problem, we can't use it because string-make-unibyte
may behave differently in different language environment.
Such a lang. env. that makes iso-8859-1 or Unicode the
highest priority for the character `À' is ok.

(string-make-unibyte (concat '(?a 192))) = "a\300"

But, if some lang. env. prefers such a charset for `À' that
encodes it not to 192 (e.g. Vietnamese VSCII), we fail.

> Note that 1-3 are not mutually exclusive so we can use
> them all.

Yes, but, at least, I really want to avoid "(3) Make a
series of new functions".

---
Ken'ichi HANDA
handa@m17n.org