Re: codepage.el: Codepage Mapping, Latin-7

[Eli Zaretskii]

> From: Reiner Steib <address@hidden>
> Cc: Eli Zaretskii <address@hidden>
> Date: Thu, 16 Mar 2006 15:35:57 +0100
> 
> from lisp/international/codepage.el:
> 
> --8<---------------cut here---------------start------------->8---
> ;; Support for the Windows 12xx series of codepages that MS has
> ;; butchered from the ISO-8859 specs. This does not add support for
> ;; the extended characters that MS has added in the 128 - 159 coding
> ;; range, only translates those characters that can be expressed in
> ;; the corresponding iso-8859 charset.
> 
> ;; Codepage Mapping:
> ;;
> ;; Windows-1250: ISO-8859-2 (Central Europe) - differs in some positions
> ;; Windows-1251: ISO-8859-5 (Cyrillic)       - differs wildly
> ;; Windows-1252: ISO-8859-1 (West Europe)    - exact match
> ;; Windows-1253: ISO-8859-7 (Greek)          - differs in some positions
> ;; Windows-1254: ISO-8859-9 (Turkish)        - exact match
> ;; Windows-1255: ISO-8859-8 (Hebrew)         - exact match
> ;; Windows-1256: ISO-8859-6 (Arabic)         - half match
> ;; Windows-1257: ISO-8859-4 (Baltic)         - differs, future Latin-7
> ;; Windows-1258: VISCII (Vietnamese)         - Completely different
> --8<---------------cut here---------------end--------------->8---
> 
> I think "exact match" is a little bit misleading, because
> e.g. Windows-1252 is a superset of ISO-8859-1.  When reading the
> comment on the "128 - 159 coding range" carefully it becomes more
> clear the mapping table only refers to ISO-8859 code points.

Yes, the match is "exact" only in one direction: from ISO-8859
encoding to the codepage, but not the other way around.

It is meaningless to say that Windows-1252 is a ``superset'' of
ISO-8859-1, since these are encodings, not character sets.  The
underlying Emacs character set does not include characters which can
be encoded by Windows-1252, but codepage.el is only intersted in
encoding the ISO-8859-1 charset, not anything beyond that.

> BTW: The comment in `codepage.el' says that Latin-7 isn't official and
> the it's not supported by Emacs.  This doesn't seem to be correct
> anymore.

codepage.el is obsolete and is not developed anymore.  It is only used
by the MS-DOS port of Emacs; everything else uses code-pages.el.
codepage.el will die a natural death when the MS-DOS port dies,
probably when v23.1 is released.