[Numpy-discussion] Portable macro to get NAN, INF, positive and negative zero

Bruce Southey bsouthey@gmail....
Thu Mar 12 08:19:38 CDT 2009


David Cournapeau wrote:
> Hi,
>
>     For the record, I have just added the following functionalities to
> numpy, which may simplify some C code:
>     - NPY_NAN/NPY_INFINITY/NPY_PZERO/NPY_NZERO: macros to get nan, inf,
> positive and negative zeros. Rationale: some code use NAN, _get_nan,
> etc... NAN is a GNU C extension, INFINITY is not available on many C
> compilers. The NPY_ macros are defined from the IEEE754 format, and as
> such should be very fast (the values should be inlined).
>     - we can now use inline safely in numpy C code: it is defined to
> something recognized by the compiler or nothing if inline is not
> supported. It is NOT defined publicly to avoid namespace pollution.
>     - NPY_INLINE is a macro which can be used publicly, and has the same
> usage as inline.
>
> cheers,
>
> David
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>   
Hi,
I am curious how this relates to Zach's comment in the thread on 
'Infinity Definitions':
http://mail.scipy.org/pipermail/numpy-discussion/2008-July/035740.html

> If I recall correctly, one reason for the plethora of infinity  
> definitions (which had been mentioned previously on the list) was that  
> the repr for some or all float/complex types was generated by code in  
> the host OS, and not in numpy. As such, these reprs were different for  
> different platforms. As there was a desire to ensure that reprs could  
> always be evaluated, the various ways that inf and nan could be spit  
> out by the host libs were all included.
>
> Has this been fixed now, so that repr(inf), (etc.) looks identical on  
> all platforms?

If this is no longer a concern then we should be able to remove those 
duplicate definitions and use of uppercase.

Bruce



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