Re: yet more Gnus questions & problems

[Luc Van Eycken <Luc.VanEycken@esat.kuleuven.ac.be>]

Lars Magne Ingebrigtsen writes:
 > jbw@cs.bu.edu (Joe Wells) writes:
 > 
 > > 2. Can Gnus be made to work with a compressed mail folder via nnfolder?  I
 > >    have a bunch of old mail archives that I would like to keep compressed
 > >    at all times, but also access via Gnus.
 > 
 > It's a tricky question, believe it or not.  If you have a folder
 > called "things.like.tex", you obviously don't want to open it in LaTeX
 > mode.  On the other hand, if you have a folder called "things.gz", you
 > do want it to be uncompressed, quite likely.  Breakage (on files that
 > happen to end with ".tex", ".c") is much worse than missing features,
 > so Gnus (and its backends) regards all files as simple modeless text
 > files.
 > 
 > There should be a separation in Emacs handling of these issues.  ".gz"
 > handling is something quite different than ".tex" handling, so there
 > shoul be a way to suppress the latter while keeping the first.

Actually there is a difference in `auto-mode-alist'. Quoting from the
documentation:
> Alist of filename patterns vs corresponding major mode functions.
> Each element looks like (REGEXP . FUNCTION) or (REGEXP FUNCTION NON-NIL).
> (NON-NIL stands for anything that is not nil; the value does not matter.)
> Visiting a file whose name matches REGEXP specifies FUNCTION as the
> mode function to use.  FUNCTION will be called, unless it is nil.
> If the element has the form (REGEXP FUNCTION NON-NIL), then after
> calling FUNCTION (if it's not nil), we delete the suffix that matched
> REGEXP and search the list again for another match.

Modes to preprocess the contents (e.g. jka-compr) use the second form
"(REGEXP FUNCTION NON-NIL)" while ordinary modes (e.g. tex) use the first
form "(REGEXP . FUNCTION)", so you could use it to distinguish between
those two types of modes.

Best regards,

Luc