On Tue, Jun 16, 2020 at 10:55 AM Bruce Momjian <bruce@momjian.us> wrote:
On Tue, Jun 16, 2020 at 08:31:21AM +0100, Dean Rasheed wrote: > > Most common implementations do regard factorial as undefined for > anything other than positive integers, as well as following the > convention that factorial(0) = 1. Some implementations extend the > factorial to non-integer inputs, negative inputs, or even complex > inputs by defining it in terms of the gamma function. However, even > then, it is undefined for negative integer inputs.
Wow, they define it for negative inputs, but not negative integer inputs? I am curious what the logic is behind that.
It is defined as NaN (or undefined), which is not in the realm of integer numbers. You might get a clear idea of the logic from [1], where they also make a case for the error being ERRCODE_DIVISION_BY_ZERO.