saving compositions or not

[Stefan Monnier]

I've been using my silly "lambda hack" (posted on gnu.emacs.sources
a little while back) and have noticed that it has an unintended
consequence: because it uses compositions (to turn the `lambda'
keyword into a lambda letter from the greek alphabet) it ends up
modifying the file if the file is saved in emacs-mule format (which
is the format naturally chosen by Emacs for those files it seems).
That is, the composition itself is saved, so the file still works,
but it unexpectedly still appears with a lambda-char rather than
a lambda-keyword if you load it in `emacs -q --no-site-file'.

Up until here, I could consider it a feature, except that it means
that the file will look odd in a non-Emacs editor (because it
uses the emacs-mule coding-system rather than plain ASCII)
and (more importantly) that `cvs diff' will show that the file has
changed, replacing the lambda keyword with a lambda char composition.

How could I change my hack such that the composition is *not* saved
(i.e. is kept as a display-only trick which has no impact whatsoever on
the saved buffer) ?


        Stefan