Re: please consider emacs-unicode for pervasive changes

[Kenichi Handa <handa@etl.go.jp>]

In article <E17mb1H-000733-00@fencepost.gnu.org>, Richard Stallman <rms@gnu.org> writes:
>>  I think that depends.  For one thing, it will typically clobber
>>  iso-2022 files.  

>     Yes.  On reading and writing iso-2022 files, Emacs-unicode
>     may designate different charsets.  I still can't find a time
>     to fix it.

> What exactly is the nature of the problem?  "Clobber" usually means
> "destroy or ruin"; however, your statement seems to say it would alter
> the file but the altered file would still represent the correct
> characters.  Which one is it?

As Emacs-unicode unifies, for instance, character C1 of
charset CS1 and character C2 of CS2.  So, so even if an
original iso-2022-7bit file uses the different byte sequence
to represent them, when emacs reads it and write, C2 will be
encoded by the same byte sequence as C1.

It doesn't matter for Emacs because when Emacs reads that
file again, there's no difference.

It's difficult to answer the question "Are C1 and C2 the
same character?"  To Emacs-unicode (and also to Unicoders),
they are same.  To some other application, they may be
different.

But, this kind of thing happen only for such coding systems
as iso-2022-7bit, iso-latin-1-with-esc, etc (those invented
by Emacs) because they can support more than two charsets
that contains characters unified by Emacs.

Other application usually don't use such coding systems but
use iso-2022-jp, iso-2022-kr, etc.  As charsets supported by
each of them doesn't overlap (thus not unified), reading and
writing by Emacs-unicode has no problem.

---
Ken'ichi HANDA
handa@etl.go.jp