GNU bug report logs - #42147
28.0.50; pure vs side-effect-free, missing optimizations?

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Package: emacs;

Reported by: Andrea Corallo <andrea_corallo <at> yahoo.it>

Date: Tue, 30 Jun 2020 22:28:02 UTC

Severity: normal

Found in version 28.0.50

Done: Mattias Engdegård <mattiase <at> acm.org>

Bug is archived. No further changes may be made.

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From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Philipp Stephani <p.stephani2 <at> gmail.com>
Cc: Mattias Engdegård <mattiase <at> acm.org>, Paul Eggert <eggert <at> cs.ucla.edu>, Andrea Corallo <andrea_corallo <at> yahoo.it>, 42147 <at> debbugs.gnu.org
Subject: bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?
Date: Sat, 25 Jul 2020 14:10:31 -0400

> and "side-effect free" is like GCC's "pure." That is, a side-effect
> free function can dereference pointers stored in Lisp_Objects, but a
> pure function can't.

I think it's still not very satisfactory since it's written in terms of
low-level operations in the C code.

I think the current intention of our "pure" goes something along the
lines of: the function will always return the "same" (the sense of `eql`)
value (or signal the same error) when called with `eql` arguments.
IOW "the function preserves `eql`ity".


        Stefan
This bug report was last modified 4 years and 282 days ago.

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