decbe2bfb1
Previously, these functions tended to throw underflow errors for negative-infinity exponents. The correct thing per POSIX is to return 0, so let's do that instead. (Note that the SQL standard is silent on such issues, as it lacks the concepts of either Inf or NaN; so our practice is to follow POSIX whenever a corresponding C-library function exists.) Also, add a bunch of test cases verifying that exp() and power() actually do follow POSIX for Inf and NaN inputs. While this patch should guarantee that exp() passes the tests, power() will not unless the platform's pow(3) is fully POSIX-compliant. I already know that gaur fails some of the tests, and I am suspicious that the Windows animals will too; the extent of compliance of other old platforms remains to be seen. We might choose to drop failing test cases, or to work harder at overriding pow(3) for these cases, but first let's see just how good or bad the situation is. Discussion: https://postgr.es/m/582552.1591917752@sss.pgh.pa.us
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