Re: printing.el again

[Stefan]

> Does the byte-compiler do constant folding optimization or it is an ad hoc
> optimization?

It's pretty ad-hoc.  But it does do some amount of constant folding.

> Maybe this should be documented in Emacs Lisp Reference or in other
> suitable info, probably Byte Compiler Users Guide.  Also other
> byte-compiler optimizations should be documented.

Actually, I don't think optimizations should be particularly mentioned.
The interesting part of optimizing (featurep 'xemacs) is that it eliminates
spurious warnings.  There are other ways to get the same effect, such as
what is done with (if (fboundp 'foo) ...) where the test is not optimized
away, but where warnings are selectively prevented.

I think a chapter on "eliminating warnings" is in order to document the use of
(featurep 'xemacs), (fboundp 'foo), (defvar foo), (with-no-warning ...), ...


        Stefan