[SciPy-user] Re: nan puzzle

Grant Edwards grante at visi.com
Thu Jul 14 09:16:13 CDT 2005


On 2005-07-14, Robert Kern <rkern at ucsd.edu> wrote:

> Since "is" evaluates based on pointer comparisons and putting
> something in a list or extracting it again by indexing ought
> to preserve those pointers, that result shouldn't happen for
> any object, nan or otherwise.

Ah, I missed that.  That is rather odd. 

> Of course, "x is nan" is a pretty useless operation as you
> point out, and one really should be using some kind of isnan()
> function. Preferably implemented by someone other than one's
> self.  :-)

After many, many years of having to impliment stuff like that
myself in C, it's hard to get into the habit of looking around
for a pre-existing implimentation.  It turns out there are a
couple different Python modules that include an isnan()
function, and even Gnu libc now comes with one.

Apparently the world is waking up to the usefulness of NaN's.

-- 
Grant Edwards                   grante             Yow!  Hand me a pair of
                                  at               leather pants and a CASIO
                               visi.com            keyboard -- I'm living
                                                   for today!



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