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Tom Lane wrote:
> Simon Riggs <simon@[EMAIL PROTECTED]
> writes:
> > Wikipedia says that exponentiation of zero to a negative power implies
> > division by zero, so shouldn't we throw a "division by zero" error?
>
> I think it should be a specific message like "zero raised to a negative
> power is undefined". It's not like it's going to take us any extra code
> to know that we are faced with that case.
>
> BTW, I realized that SQL:2003 spells it all out for us in explicit
> detail:
....
> b) If VB is 0 (zero) and VE is negative, then an exception condition is
> raised: data exception Ñ invalid argument for power function.
Well, this indicates we shouldn't return "zero raised to a negative
power is undefined", but rather the power error we are giving now, or
are you saying we should return the "power" error code but an error
message mentioning zero?
> c) If VB is 0 (zero) and VE is 0 (zero), then the result is 1 (one).
I have updated the C comments to mention the spec also requires we
return 1 in this case.
C comment updated attached and applied.
--
Bruce Momjian <bruce@[EMAIL PROTECTED]
> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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Index: src/backend/utils/adt/float.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/adt/float.c,v
retrieving revision 1.155
diff -c -c -r1.155 float.c
*** src/backend/utils/adt/float.c 21 Apr 2008 00:26:45 -0000 1.155
--- src/backend/utils/adt/float.c 9 May 2008 15:34:53 -0000
***************
*** 1331,1337 ****
/*
* The SQL spec requires that we emit a particular SQLSTATE error code
for
! * certain error conditions.
*/
if ((arg1 == 0 && arg2 < 0) ||
(arg1 < 0 && floor(arg2) != arg2))
--- 1331,1338 ----
/*
* The SQL spec requires that we emit a particular SQLSTATE error code
for
! * certain error conditions. Specifically, we don't return a
divide-by-zero
! * error code for 0 ^ -1.
*/
if ((arg1 == 0 && arg2 < 0) ||
(arg1 < 0 && floor(arg2) != arg2))
Index: src/backend/utils/adt/numeric.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/adt/numeric.c,v
retrieving revision 1.112
diff -c -c -r1.112 numeric.c
*** src/backend/utils/adt/numeric.c 8 May 2008 22:17:54 -0000 1.112
--- src/backend/utils/adt/numeric.c 9 May 2008 15:34:53 -0000
***************
*** 1893,1900 ****
trunc_var(&arg2_trunc, 0);
/*
! * Return special SQLSTATE error codes for a few conditions mandated by
! * the standard.
*/
if ((cmp_var(&arg1, &const_zero) == 0 &&
cmp_var(&arg2, &const_zero) < 0) ||
--- 1893,1901 ----
trunc_var(&arg2_trunc, 0);
/*
! * The SQL spec requires that we emit a particular SQLSTATE error code
for
! * certain error conditions. Specifically, we don't return a
divide-by-zero
! * error code for 0 ^ -1.
*/
if ((cmp_var(&arg1, &const_zero) == 0 &&
cmp_var(&arg2, &const_zero) < 0) ||
***************
*** 5283,5288 ****
--- 5284,5290 ----
/*
* While 0 ^ 0 can be either 1 or indeterminate (error), we
* treat it as 1 because most programming languages do this.
+ * SQL:2003 also requires a return value of 1.
* http://en.wikipedia.org/wiki/Exponentiation#Zero_to_the_zero_power
*/
set_var_from_var(&const_one, result);
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