[Python-Dev] Why is nan != nan?

[Jesus Cea]

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On 03/25/2010 07:54 AM, Georg Brandl wrote:
>>>>>> float('nan') in [float('nan')]
>>> False
>>
>> Sure, but just think of it as having two different nans there.  (You
>> could imagine thinking of the id of the nan as part of the payload.)
> 
> That's interesting.  Thinking of each value created by float('nan') as
> a different nan makes sense to my naive mind, and it also explains
> nicely the behavior present right now.  Each nan comes from a different
> operation and therefore is a "different" non-number.

Infinites are "not equal" for a good reason, for example.

1/0 and 2/0 are both infinites, but one is "greater" than the other. Or
(1/0)^(1/0), an infinite infinitelly "bigger".

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