Re: bug in numeric_power() function

> -----Original Message-----
> From: pgsql-hackers-owner(at)postgresql(dot)org [mailto:pgsql-hackers-
> owner(at)postgresql(dot)org] On Behalf Of Richard Wang
> Sent: Tuesday, March 11, 2008 7:38 PM
> To: pgsql-hackers(at)postgresql(dot)org
> Subject: [HACKERS] bug in numeric_power() function
>
> I expected 0 ^ 123.3 to be 0, but it reported error as follows
>
> postgres=# select 0 ^ 123.3;
> ERROR: cannot take logarithm of zero
>
> I find that there is a bug in numeric_power() function
> the function caculates a ^ b based on the algorithm e ^ (lna * b)
> as you see, ln0 is not valid

It seems an obvious work-around that:
if (b == 0) return 1;
if (a == 0) return 0;
could be inserted at the top.

Aside:
Having the ^ operator overloaded for exponentiation surprises me.

Does it really have the right precedence for performing exponentiation?
(E.g. you cannot do this in C++ because ^ will have the precedence of
xor, which is wrong).