On Sat, Oct 29, 2016 at 11:44 PM, Stephan Hoyer <sho...@gmail.com> wrote:
> I'm have more mixed fillings on testing for NaNs. NaNs propagate, so
> explicit testing is rarely needed. Also, in numerical computing we usually
> work with arrays of NaN, so operator.exists() and all this nice syntax
> would not be a substitute for numpy.isnan or pandas.isnull.
>
NaN's *usually* propagate. The NaN domain isn't actually closed under IEEE
754.
>>> nan, inf = float('nan'), float('inf')
>>> import math
>>> nan**0
1.0
>>> math.hypot(nan, inf)
inf
>>> min(1, nan)
1
The last one isn't really mandated by IEEE 754, and is weird when you
consider `min(nan, 1)`.
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