Can emacs pick proper coding system intelligently?

Can emacs pick proper coding system intelligently?

[Scott Heftler]

Yesterday I have a problem.  I would read a RMAIL-mode file saved via
`gnus-summary-save-in-rmail' and the ellipses would be escape-quoted
and display as \205.

I was told that I needed to find the file using windows-1252 as my
coding system.  Now the windows-1252 ellipses display nicely when I
run `universal-coding-system-argument' (C-x RET c windows-1252) before
finding the file.

You'd think that, when emacs encounters these \205s, it would KNOW to
pick windows-1252.  But it doesn't.  I put these in my init file to 
help it along:

(prefer-coding-system 'windows-1252)
(prefer-coding-system 'utf-8)

This makes sure utf-8 is top pick, and windows-1252 is second.  This 
did nothing.

Is there no way to AUTOMATE emacs' pick of coding system?  I thought
it chose coding systems intelligently, based on file contents?  Do I
really have to open a file, see escape-quoted characters, guess what
coding system I should use, close the file, and then reopen it using
`C-x RET c' in a trial-and-error fashion?

-- Scott

Re: Can emacs pick proper coding system intelligently?

[Barry Margolin]

In article <m2mynekfox.fsf@mac.com>,
 Scott Heftler <lovecraftian@mac.com> wrote:

> You'd think that, when emacs encounters these \205s, it would KNOW to
> pick windows-1252.

How would it know that.  \205 is not unique to that coding system, it 
exists in many different coding systems.

Think of it like Paint By Numbers.  The coding system is the translation 
from numbers to colors.  You can't just look at a picture, and know 
which translation scheme to use just because it contains the number 10.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

Re: Can emacs pick proper coding system intelligently?

[Scott Heftler]

Wait a minute!  I forgot to mention that, when the article was first 
loaded from usenet, it looked perfect -- there WERE no escaped 
characters.  Only after saving and then re-opening did these post-127 
chars get escaped.  Why can't gnus/emacs save the RMAIL file with some 
kind of "open-me-with-coding-system"-type info?
-- 
Scott Heftler
 psyche@mail.utexas.edu
 Man muß mit den Wölfen heulen.

Re: Can emacs pick proper coding system intelligently?

[Eli Zaretskii]

> From: Scott Heftler <lovecraftian@mac.com>
> Date: Sun, 27 Apr 2008 19:04:30 -0500
> 
> Is there no way to AUTOMATE emacs' pick of coding system?  I thought
> it chose coding systems intelligently, based on file contents?

It does when it can.  Unfortunately, with 8-bit encodings, they are
too similar to distinguish between them reliably and efficiently.

However, if you have specific suggestions for improvements in this
area, please feel free to post them to emacs-devel@gnu.org.