[SciPy-user] Re: nan puzzle

Howey, David A d.howey at imperial.ac.uk
Wed Jul 27 10:57:25 CDT 2005


Just found this, thought it might be of interest-- gurus probably know this already, I wasn't aware:
http://www.cs.ucla.edu/classes/winter04/cs131/hw/hw4.html
 
Dave

________________________________

From: scipy-user-bounces at scipy.net on behalf of Grant Edwards
Sent: Wed 13/07/2005 05:16
To: scipy-user at scipy.org
Subject: [SciPy-user] Re: nan puzzle



On 2005-07-13, Alan G Isaac <aisaac at american.edu> wrote:

> Is this expected behavior?

>>>> x is nan
> True
>>>> x=z[2]
>>>> x
> -1.#IND
>>>> x is nan
> False

May I ask why you care? 

The expression "x is nan" seems pretty useless to me.  The "is"
operator isn't really useful for other floating point values,
why would it be useful for nans?

>>> x = 1.234
>>> x is 1.234
False
>>>
>>> y = 1.234
>>> x is y
False
>>> x == y
True
>>>

What you probably want to be checking is if x has a nan value,
not whether x is the same object as some other object that
has a nan value.

--
Grant Edwards                   grante             Yow!  Is this my STOP??
                                  at              
                               visi.com           

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