在 2019/7/31 下午1:13, sisyphus 写道: > Martin, > Thanks for all your work. > I couldn't locate mingw-w64-crt/math/x86/pow.def.h on the internet (URL ?), > but I assume the patch is concerned with raising a NaN to a power. > Given that raising an input NaN to a power does not always result in a NaN, > it seems a little suspicious that this has come up under the subject > "properly propagate input NANs". > > In short - I'm simply seeking reassurance that the case of raising a NaN to > the power of zero is still being correctly handled. >
See <http://pubs.opengroup.org/onlinepubs/9699919799/functions/pow.html> for details. According to the POSIX standard, not all mathematical functions involving NaNs return NaNs. This list is informative only and might be incomplete: 0) `pow(1.0, y)` returns `1.0`, no matter what `y` is. 1) `pow(x, 0.0)` returns `0.0`, no matter what `x` is. 2) `fmax(x, y)` and `fmin(x, y)` returns the other argument if either argument is a NaN. 3) `hypot(x, y)` returns a positive infinity if either argument is an infinity, no matter what the other argument is. 4) `copysign(x, y)` does not return a NaN when `x` is not a NaN but `y` is. -- Best regards, LH_Mouse
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