On 10/25/2012 10:44 PM, Steven D'Aprano wrote:
On Thu, 25 Oct 2012 22:04:52 -0400, Terry Reedy wrote:
It is a consequence of the following, which some people (but not all)
believe is mandated by the IEEE standard.
>>> nan = float('nan')
>>> nan is nan
True
The IEEE 754 standard says nothing about object identity. It only
discusses value equality.
>>> nan == nan
False
IEEE 754 states that all NANs compare unequal to everything, including
NANs with the same bit value. It doesn't make an exception for
comparisons with itself.
I'm not entirely sure why you suggest that there is an argument about
what IEEE 754 says about NANs.
I did not do so.
As far as I can see, the argument is
whether or not language designers should pick and choose which bits of
the standard they want to follow, thus taking a step backwards to the
chaos of numerical computing prior to the IEEE 754 standard.
There has been disagreement about whether the standard mandates that
Python behave the way it does. That is a fact, but I have no interest in
discussing the issue.
--
Terry Jan Reedy
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