Alvaro Herrera wrote:
> Bruce Momjian wrote:
> > Tom Lane wrote:
> > > Bruce Momjian <bruce@momjian.us> writes:
> > > > I have developed the attached patch which fixes 0 ^ 123.3.
> > >
> > > Did you actually read the wikipedia entry you cited?
>
> But that's about 0^0, not about 0^123.3. See this other subsection:
>
> http://en.wikipedia.org/wiki/Exponentiation#Powers_of_zero
>
> 0^123.3 is 0, not 1.
Ah, got it, and I updated the patch to remove the commment about
"discrete".
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
Index: src/backend/utils/adt/numeric.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/adt/numeric.c,v
retrieving revision 1.110
diff -c -c -r1.110 numeric.c
*** src/backend/utils/adt/numeric.c 21 Apr 2008 00:26:45 -0000 1.110
--- src/backend/utils/adt/numeric.c 7 May 2008 23:18:31 -0000
***************
*** 5170,5175 ****
--- 5170,5190 ----
int local_rscale;
double val;
+ /*
+ * This avoids log(0) for cases of 0 raised to a non-integer.
+ * Also, while 0 ^ 0 can be either 1 or indeterminate (error), we
+ * treat it as one because most programming languages do this.
+ * http://en.wikipedia.org/wiki/Exponentiation#Zero_to_the_zero_power
+ */
+ if (cmp_var(base, &const_zero) == 0)
+ {
+ if (cmp_var(exp, &const_zero) == 0)
+ set_var_from_var(&const_one, result);
+ else
+ set_var_from_var(&const_zero, result);
+ return;
+ }
+
/* If exp can be represented as an integer, use power_var_int */
if (exp->ndigits == 0 || exp->ndigits <= exp->weight + 1)
{
***************
*** 5266,5280 ****
NumericVar base_prod;
int local_rscale;
- /* Detect some special cases, particularly 0^0. */
-
switch (exp)
{
case 0:
- if (base->ndigits == 0)
- ereport(ERROR,
- (errcode(ERRCODE_FLOATING_POINT_EXCEPTION),
- errmsg("zero raised to zero is undefined")));
set_var_from_var(&const_one, result);
result->dscale = rscale; /* no need to round */
return;
--- 5281,5289 ----