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From: <tomas@tuxteam.de>
To: help-gnu-emacs@gnu.org
Subject: Re: Bit shift oddity?
Date: Mon, 19 Oct 2020 09:06:10 +0200	[thread overview]
Message-ID: <20201019070610.GB9024@tuxteam.de> (raw)
In-Reply-To: <880f79e9-e2ea-b180-d83f-c3d47f5fb789@gmail.com>

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On Sun, Oct 18, 2020 at 08:19:24PM -0400, Douglas Lewan wrote:
> I see the following:
> 
>    ELISP> (= (lsh -1 (lognot 0)) (lsh -2 (lognot 0)))
> 
>    t
> 
>    ELISP> (= (lsh -1 (lognot 0)) (lsh -3 (lognot 0)))
> 
>    nil
> 
> The first seems odd to me. Is it really what's expected?

The manual for lsh talks about "quirky behaviour" of lsh when
both arguments are negative, in the name of backward-compatibility
and suggests resorting to ash. Cf. the Emacs lisp manual "3.8
Bitwise Operations on Integers"

Cheers
 - t

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  reply	other threads:[~2020-10-19  7:06 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-19  0:19 Bit shift oddity? Douglas Lewan
2020-10-19  7:06 ` tomas [this message]
2020-10-19  7:48   ` Douglas Lewan
2020-10-19  9:01     ` tomas
2020-10-19 15:14       ` Stefan Monnier
2020-10-19 15:30         ` tomas
2020-10-19  9:23 ` Gregory Heytings via Users list for the GNU Emacs text editor
2020-10-19 15:19   ` Douglas Lewan

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