| From: | Chapman Flack <chap(at)anastigmatix(dot)net> |
|---|---|
| To: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, Vik Fearing <vik(dot)fearing(at)2ndquadrant(dot)com> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Greatest Common Divisor |
| Date: | 2019-12-29 16:50:15 |
| Message-ID: | 5E08D947.9000902@anastigmatix.net |
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| Lists: | pgsql-hackers |
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
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