Bruce Evans e95cc9b700 Fix tgamma() on some special args: ... (1) tgamma(-Inf) returned +Inf and failed to raise any exception, but should always have raised an exception, and should behave like tgamma(negative integer). (2) tgamma(negative integer) returned +Inf and raised divide-by-zero, but should return NaN and raise "invalid" on any IEEEish system. (3) About half of the 2**52 negative intgers between -2**53 and -2**52 were misclassified as non-integers by using floor(x + 0.5) to round to nearest, so tgamma(x) was wrong (+-0 instead of +Inf and now NaN) on these args. The floor() expression is hard to use since rounding of (x + 0.5) may give x or x + 1, depending on |x| and the current rounding mode. The fixed version uses ceil(x) to classify x before operating on x and ends up being more efficient since ceil(x) is needed anyway. (4) On at least the problematic args in (3), tgamma() raised a spurious inexact. (5) tgamma(large positive) raised divide-by-zero but should raise overflow. (6) tgamma(+Inf) raised divide-by-zero but should not raise any exception. (7) Raise inexact for tiny |x| in a way that has some chance of not being optimized away. The fix for (5) and (6), and probably for (2), also prevents -O optimizing away the exception. PR: 112180 (2) Standards: Annex F in C99 (IEC 60559 binding) requires (1), (2) and (6).		2007-05-02 15:24:49 +00:00
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b_exp.c
b_log.c
b_tgamma.c	Fix tgamma() on some special args:	2007-05-02 15:24:49 +00:00
mathimpl.h