Re: Greatest Common Divisor

Vik Fearing <vik.fearing@2ndquadrant.com> writes:
> On 04/01/2020 01:21, Tom Lane wrote:
>> Zero is the "correct" answer for that, isn't it, independently of overflow
>> considerations?  

> I would say not.

Oh, right, I was misremembering the identity gcd(a,0) as being 0 not a.
Never mind that then.

> The correct answer is INT_MIN but we've decided a
> negative result is not desirable.

Agreed.  On the other hand, we could stave off overflow the same
way we discussed for lcm: make it return int8.  We're still stuck
with the special case for INT64_MIN in gcd64 of course, so maybe
that's just inconsistent rather than being worthwhile.

[ thinks for a bit... ]  In practice, I imagine few people use gcd on
negative values, so doing weird things with the datatype choices is
probably not better than throwing an error for this case.

            regards, tom lane