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Re: byte-opt.el addition - optimize list of compile-time constants


From: Stefan Monnier
Subject: Re: byte-opt.el addition - optimize list of compile-time constants
Date: Wed, 08 Dec 2004 18:40:42 -0500
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/21.3.50 (gnu/linux)

> (disassemble 
>   (lambda nil 
>     `(:a 1 :b 2 
>       :c ,#'(lambda nil (when (eq (following-char) ?\n) (forward-char 1))))))
[...]
> second place, byte-optimize-pure-func is called, but the optimization
> fails because a (function ...) form appears inside the arguments to
> list, which does not count as byte-compile-constp.  This is the other

Hmm... we should probably update byte-compile-constp to accept
(function ...) just like it accepts (quote ...).

> problem I mentioned earlier - at the point at which the
> 'byte-optimizer function for list is called, the inner function has
> not yet been compiled, contrary to the general principle that the byte
> optimizer operates depth-first.

The "byte-optimizer" has two phases: one done before byte-compilation and
one after.  The byte-optimize-pure-func is done before.

As for your particular problem, there's an easier solution:

    (defun foo-aux nil (when (eq (following-char) ?\n) (forward-char 1))
    ...
    (lambda nil
      '(:a 1 :b 2 :c foo-aux))


-- Stefan




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