bug#42597: closed (27.1; (+ -0.0) returns +0.0 when compiled)

[GNU bug Tracking System]

Your message dated Fri, 7 Aug 2020 10:50:19 +0200
with message-id <8E812D2B-DAFD-433F-8A77-44946CD51F4F@acm.org>
and subject line Re: bug#42597: 27.1; (+ -0.0) returns +0.0 when compiled
has caused the debbugs.gnu.org bug report #42597,
regarding 27.1; (+ -0.0) returns +0.0 when compiled
to be marked as done.

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42597: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=42597
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> --- Begin Message ---
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> Subject: 
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> 27.1; (+ -0.0) returns +0.0 when compiled
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> Date: 
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> Wed, 29 Jul 2020 14:07:32 +0200
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> Unary +, *, min and max, all of which should be identity for numbers, convert 
> -0.0 to +0.0 when byte-compiled:
>
> (defun f (x) (+ x))
> (f -0.0)
> => -0.0
> (byte-compile 'f)
> (f -0.0)
> => 0.0
>
> The reason is that byte-compile-associative transforms (+ x), (* x), (min x) 
> and (max x) into (+ x 0).
>
> No patch yet (sorry!) but I'm not sure what would be the best way to go about 
> it. Some possibilities:
>
> A. Use a full 1-argument call, like (+ x). This is more expensive (about 1.8×) 
> since the general function call mechanism has to be used.
> B. Use (* x 1) instead; this appears to work. This is also more expensive 
> (1.6×); not sure why.
> C. Add a new byte-op. Fast but probably overkill.
>
> Better suggestions welcome!
>
>
>
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> --- End Message ---
> --- Begin Message ---
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> Subject: 
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> Re: bug#42597: 27.1; (+ -0.0) returns +0.0 when compiled
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> Date: 
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> Fri, 7 Aug 2020 10:50:19 +0200
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> No immediate objections at least; patches pushed to master.
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> --- End Message ---