[Python-Dev] Why is nan != nan?
Stephen J. Turnbull
stephen at xemacs.org
Fri Mar 26 05:39:55 CET 2010
Steven D'Aprano writes:
> But unlike us, the equality operator only has a pinhole view of the
> operands. It can't distinguish between your example and this:
> x = float('nan')
> y = some_complex_calculation(x)
> if x == y:
> where y merely happens to end up with the same object as x by some quirk
> of implementation.
Note that Mark has already provided a related example of such a quirk
(Decimal(-1).sqrt(), I think it was).
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