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

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From: Mattias Engdegård <mattiase <at> acm.org>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: Stefan Monnier <monnier <at> iro.umontreal.ca>, 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: Fri, 3 Jul 2020 11:32:35 +0200

2 juli 2020 kl. 22.09 skrev Paul Eggert <eggert <at> cs.ucla.edu>:

>> Note that it can also be done without slowing down `eq` (by
>> hash-consing the bignums).
> 
> Yes, that's a better way to go. I wrote a patch to do that a while ago but never
> got around to the laborious part, which was benchmarking.

Hash-consing bignums may be a good idea (I'm neutral on the idea), but there could be a reason why it isn't very commonly seen in other runtimes; perhaps they have more efficient GCs (generational and/or incremental), but Emacs would benefit (a lot) from that, too.

In any case, it's a one-way decision: once we guarantee eq to provide numerical equality (whether by hash-consing or otherwise), there is no way back.

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