[Numpy-discussion] What is the sign of nan?

David Cournapeau david@ar.media.kyoto-u.ac...
Tue Sep 30 00:56:29 CDT 2008


Nathan Bell wrote:
>
> +1 for NaN-always-propagates since we have explicit variants for the
> alternative semantics.
>
> Users are more likely to remember that "NaNs always propagate" than
> "as stated in the C99 standard...".

I don't know. I would like to agree with you, but OTOH, starting to go
against the C99 standard may bring us quite far. FWIW, matlab has the
same behavior as mandated by C99 (but not R, by default).

The problem I have with fmax is that:
    - isgreaterequal may be slow ? May well be red-herring.
    - I guess isgreaterequal is not available on windows with MS compilers
    - we can't detect NaN with FPE_INVALID (since by definition
isgreaterequal never raises it), hence can't detect it with seterr.

This is starting to get mind-blowing...

cheers,

David



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