emacs-unicode-2: cpNNN and ibmNNN coding systems

[Reiner Steib]

Hi,

in emacs-unicode-2, the coding systems ibm437 and cp437 are aliases:

,----[ M-x describe-coding-system RET ibm437 RET ]
| D -- ibm437 (alias of cp437)
| 
| DOS codepage 437
| Type: charset (charset)
| EOL type: Automatic selection from:
|       [cp437-unix cp437-dos cp437-mac]
| This coding system encodes the following charsets:
|   cp437
`----

However, according to
<ftp://ftp.unicode.org/Public/MAPPINGS/VENDORS/IBM/README.TXT>, there
are minor (?) differences between the Microsoft and IBM mappings:

,----[ <ftp://ftp.unicode.org/Public/MAPPINGS/VENDORS/IBM/README.TXT> ]
| Code Pages 00437 (US etc.)
|            00860 (Portugal)
|            00861 (Iceland)
|            00862 (Israel)
|            00863 (Canadian French)
|            00865 (Nordic)
| 
|       Microsoft                         IBM
|       ---------                       -----
| 0x1A      U001A                       U001C
| 0x1C      U001C                       U007F
| 0x7F      U007F                       U001A
| 0xE6      U00B5 (MICRO SIGN)          U03BC (GREEK SMALL LETTER MU)
| 
| The "rotation" of the control characters at 0x1A, 0x1C and
| 0x7F is due to the frequent use of 0x1A as end-of-file by
| PC file systems and applications.
`----

I don't know if these and the differences in other code pages
mentioned there are worth to make different coding systems instead of
aliases.

If not, would it make sense to add aliases for ibmNNN in the trunk as
well?

[ Background: Today there was a posting with "charset=IBM437" in
  de.comp.text.tex (<news:address@hidden>).  I thought
  of adding an alias (ibm437 . cp437) in `mm-charset-synonym-alist'
  (Gnus), but I wasn't sure if it's correct. ]

Bye, Reiner.
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/