NaN comparisons - Call For Anecdotes

Ethan Furman ethan at
Wed Jul 9 18:42:28 CEST 2014

On 07/08/2014 07:53 AM, Anders J. Munch wrote:
> So I make this claim: float.__eq__ implementing IEEE-754 NaN
> comparison rules creates real problems for developers. And it has
> never, ever, helped anyone do anything.
> "Never" is a strong claim, and easily disproven if false: Simply
> provide a counterexample.  So that is my challenge: If you have a
> program (a pre-existing and useful one, not something artificial
> created for this challenge) that benefits from NaN!=NaN and that would
> fail if x==x for all float objects x, then please come forward and
> show it, and I'll buy you a beer the next time I'm at PyCon.

I would suggest you ask for this on the numerical mailing lists instead of here -- and you may not want to offer a beer 
to everyone that has an anecdote for NaN behavior being useful.


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