From: "Mattias Engdegård" <mattiase@acm.org>
To: Po Lu <luangruo@yahoo.com>
Cc: Eli Zaretskii <eliz@gnu.org>,
stefankangas@gmail.com, 56641@debbugs.gnu.org
Subject: bug#56641: Deprecate `lsh`
Date: Thu, 21 Jul 2022 09:47:52 +0200 [thread overview]
Message-ID: <759888C8-0176-4293-BA47-984EB3E7061B@acm.org> (raw)
In-Reply-To: <87y1wn8ckv.fsf@yahoo.com>
21 juli 2022 kl. 03.43 skrev Po Lu <luangruo@yahoo.com>:
> Which is the obvious use? For compatibility with programs (not
> necessarily within Emacs) that expect different values based on the
> number of VALBITs in the Emacs machine file?
Honestly I don't know. Even before Emacs 27, `lsh` seems a bit questionable since the width is both platform-dependent and unlike C, say, isn't a particularly useful size. It doesn't correspond to anything in hardware, isn't a power of two or anything like that.
It could be code that expects (lsh x -29) to return the sign bit as 1 or 0, as some kind of 'optimisation', what do I know.
Also see bug#32463 for some discussion about lsh during the transition to bignums. Basically everyone agreed that it's useless but that it probably needs to be kept for compatibility in some way.
next prev parent reply other threads:[~2022-07-21 7:47 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-19 13:38 bug#56641: Deprecate `lsh` Mattias Engdegård
2022-07-19 13:52 ` Eli Zaretskii
2022-07-19 14:44 ` Stefan Kangas
2022-07-19 15:40 ` Eli Zaretskii
2022-07-19 15:53 ` Mattias Engdegård
2022-07-19 16:20 ` Stefan Kangas
2022-07-19 16:38 ` Eli Zaretskii
2022-07-20 1:25 ` Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-07-20 2:36 ` Eli Zaretskii
2022-07-20 3:20 ` Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-07-20 11:24 ` Eli Zaretskii
2022-07-20 11:57 ` Mattias Engdegård
2022-07-20 12:21 ` Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-07-20 12:44 ` Eli Zaretskii
2022-07-20 14:30 ` Mattias Engdegård
2022-07-21 1:43 ` Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-07-21 7:47 ` Mattias Engdegård [this message]
2022-07-23 7:26 ` Lars Ingebrigtsen
2022-07-23 10:32 ` Mattias Engdegård
2022-07-23 11:20 ` Lars Ingebrigtsen
2022-07-23 13:18 ` Eli Zaretskii
2022-07-23 13:20 ` Lars Ingebrigtsen
2022-07-23 15:42 ` Basil L. Contovounesios via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-07-23 16:51 ` Mattias Engdegård
2022-07-24 3:38 ` Basil L. Contovounesios via Bug reports for GNU Emacs, the Swiss army knife of text editors
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