On 2/13/19 12:32 PM, Marko Rauhamaa wrote:
"Avi Gross" <avigr...@verizon.net>:
A NaN is a bit like a black hole. Anything thrown in disappears and
that is about all we know about it. No two black holes are the same
even if they seem to have the same mass, spin and charge. All they
share is that we don't know what is in them.
Then, how do you explain:
>>> float("nan") != float("nan")
True
Why's that not False?
Marko
Because IEEE-754 decided that it was non-optional that (x != y) was
equal to not (x == y). Which is not the case for the ordering
operators, since ordering is inherently undefined.
In part, these decisions were made to make it possible to detect a NaN
in C in the absence of an isnan() function. If (x != x), then x must be
a NaN.
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