Horton

Re: Greatest Common Divisor

Tom Lane <tgl@sss.pgh.pa.us>

View thread View on postgr.es
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Vik Fearing <vik.fearing@2ndquadrant.com>
Cc: Fabien COELHO <coelho@cri.ensmp.fr>, Stephen Frost <sfrost@snowman.net>, Dean Rasheed <dean.a.rasheed@gmail.com>, Chapman Flack <chap@anastigmatix.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2020-01-04T00:21:17Z
Lists: pgsql-hackers 
Vik Fearing <vik.fearing@2ndquadrant.com> writes:
> On 03/01/2020 20:14, Fabien COELHO wrote:
>> I'm unsure about gcd(INT_MIN, 0) should error. Possibly 0 would be nicer?

> What justification for that do you have?

Zero is the "correct" answer for that, isn't it, independently of overflow
considerations?  We should strive to give the correct answer if it's known
and representable, rather than have arbitrary failure conditions.

(IOW, we should throw errors only when the *result* is out of range
or undefined, not just because the input is an edge case.)

			regards, tom lane

Commits

  1. Add functions gcd() and lcm() for integer and numeric types.