From: "Mattias Engdegård" <mattiase@acm.org>
To: Andrea Corallo <akrl@sdf.org>
Cc: 42147-done@debbugs.gnu.org, Paul Eggert <eggert@cs.ucla.edu>,
Stefan Monnier <monnier@iro.umontreal.ca>,
Andrea Corallo <andrea_corallo@yahoo.it>
Subject: bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?
Date: Thu, 9 Jul 2020 12:20:34 +0200 [thread overview]
Message-ID: <4A6D5CD1-031E-4DF8-9FE5-365DF17E14CA@acm.org> (raw)
In-Reply-To: <xjfo8opmyyz.fsf@sdf.org>
9 juli 2020 kl. 00.19 skrev Andrea Corallo <akrl@sdf.org>:
> Or is it maybe that the only way to certainly have a mutable string is
> with `copy-sequence' or `make-string'?
Yes; since the need for a mutable value is very unlikely, creating a fresh copy every time just in case would be a big waste of resources. Otherwise, we could only 'optimise'
(concat "abc" "def")
to
(copy-sequence "abcdef")
which would be a very modest improvement, for very little gain.
The two functions you mentioned are indeed guaranteed to return fresh, mutable strings and thus cannot be marked 'pure'.
String mutation is something of a special case: it is rare, yet its mere possibility incurs costs even for code that doesn't use it. Better try to keep that cost to a minimum.
next prev parent reply other threads:[~2020-07-09 10:20 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1583748933.1069307.1593556032592.ref@mail.yahoo.com>
2020-06-30 22:27 ` bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations? Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-06-30 23:14 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-01 12:46 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-01 12:44 ` Mattias Engdegård
2020-07-01 16:08 ` Mattias Engdegård
2020-07-01 21:31 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-02 10:26 ` Mattias Engdegård
2020-07-02 10:59 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-02 12:46 ` Mattias Engdegård
2020-07-02 13:56 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-02 14:51 ` Mattias Engdegård
2020-07-02 15:32 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-02 15:49 ` Stefan Monnier
2020-07-02 18:01 ` Mattias Engdegård
2020-07-02 18:55 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-02 19:38 ` Stefan Monnier
2020-07-02 20:09 ` Paul Eggert
2020-07-03 9:32 ` Mattias Engdegård
2020-07-03 13:39 ` bug#42147: Hash-consing bignums (was: bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?) Stefan Monnier
2020-07-02 20:31 ` bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations? Paul Eggert
2020-07-02 21:41 ` Stefan Monnier
2020-07-02 23:16 ` Paul Eggert
2020-07-03 8:32 ` Mattias Engdegård
2020-07-03 13:11 ` Stefan Monnier
2020-07-03 18:35 ` Mattias Engdegård
2020-07-03 18:43 ` Mattias Engdegård
2020-07-03 19:05 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-04 14:58 ` Mattias Engdegård
2020-07-04 15:06 ` Stefan Monnier
2020-07-04 16:13 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-05 13:00 ` Mattias Engdegård
2020-07-05 13:16 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-06 17:20 ` Mattias Engdegård
2020-07-06 21:23 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-07 15:54 ` Mattias Engdegård
2020-07-07 16:24 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-07 16:55 ` Mattias Engdegård
2020-07-07 17:42 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-08 19:14 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-08 21:25 ` Mattias Engdegård
2020-07-08 22:19 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-09 10:20 ` Mattias Engdegård [this message]
2020-07-09 12:47 ` Stefan Monnier
2020-07-09 12:57 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-09 14:35 ` Stefan Monnier
2020-07-09 15:19 ` Paul Eggert
2020-07-09 15:37 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-05 15:26 ` Mattias Engdegård
2020-07-03 18:31 ` Paul Eggert
2020-07-03 18:47 ` Mattias Engdegård
2020-07-04 15:57 ` Paul Eggert
2020-07-04 16:15 ` Eli Zaretskii
2020-07-04 16:27 ` Paul Eggert
2020-07-04 16:33 ` Stefan Monnier
2020-07-04 16:44 ` Mattias Engdegård
2020-07-04 17:00 ` Paul Eggert
2020-07-04 18:37 ` Pip Cet
2020-07-04 21:05 ` Stefan Monnier
2020-07-04 22:25 ` Pip Cet
2020-07-05 2:38 ` Eli Zaretskii
2020-07-05 8:28 ` Paul Eggert
2020-07-05 8:39 ` Andreas Schwab
2020-07-05 14:47 ` Eli Zaretskii
2020-07-05 15:30 ` Stefan Monnier
2020-07-06 0:14 ` Paul Eggert
2020-07-05 15:11 ` Stefan Monnier
2020-07-06 0:10 ` Paul Eggert
2020-07-05 9:56 ` Paul Eggert
2020-07-05 10:03 ` Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-07-05 23:57 ` Paul Eggert
2020-07-04 19:01 ` Mattias Engdegård
2020-07-04 17:10 ` Eli Zaretskii
2020-07-04 19:26 ` Paul Eggert
2020-07-02 19:09 ` Philipp Stephani
2020-07-03 9:25 ` Mattias Engdegård
2020-07-25 17:09 ` Philipp Stephani
2020-07-25 18:10 ` Stefan Monnier
2020-07-25 20:03 ` Philipp Stephani
2020-07-25 20:07 ` Stefan Monnier
2020-07-25 20:11 ` Philipp Stephani
2020-07-25 21:00 ` Mattias Engdegård
2020-07-25 21:29 ` Stefan Monnier
2020-07-25 21:39 ` Philipp Stephani
2020-07-25 22:27 ` Stefan Monnier
2020-07-29 12:53 ` Philipp Stephani
2020-07-29 14:28 ` Stefan Monnier
2020-07-25 21:54 ` Mattias Engdegård
2020-07-25 22:30 ` Stefan Monnier
2020-07-26 9:05 ` Mattias Engdegård
2020-07-29 16:03 ` Mattias Engdegård
2020-07-29 20:39 ` Stefan Monnier
2020-08-03 15:07 ` Mattias Engdegård
2020-08-10 13:39 ` Philipp Stephani
2020-08-10 22:07 ` Stefan Monnier
2020-08-10 13:42 ` Philipp Stephani
2020-08-10 22:10 ` Stefan Monnier
2020-07-29 13:10 ` Philipp Stephani
2020-07-25 21:09 ` Stefan Monnier
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