Message-ID: <5E08D947.9000902@anastigmatix.net>
Date: Sun, 29 Dec 2019 11:50:15 -0500
From: Chapman Flack <chap@anastigmatix.net>
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To: Fabien COELHO <coelho@cri.ensmp.fr>,
 Vik Fearing <vik.fearing@2ndquadrant.com>
CC: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Greatest Common Divisor
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On 12/29/19 02:30, Fabien COELHO wrote:

>>> C modulo operator (%) is a pain because it is not positive remainder
>>> (2 % -3 == -1 vs 2 % 3 == 2, AFAICR).
>>
>> This does not seem to be the case...
> ...
> Because I do not trust C modulo as I had a lot of problems with it? :-)

If I recall correctly (and I'm traveling and away from those notes),
the exact semantics of C's % with negative operands was left
implementation-defined until, was it, C99 ?

So it might be ok to rely on the specified C99 behavior (whichever
behavior that is, he wrote, notelessly) for PG 12 and later, where
C99 is expected.

Regards,
-Chap