tjreedy at udel.edu
Fri Oct 26 09:54:02 CEST 2012
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
> The IEEE 754 standard says nothing about object identity. It only
> discusses value equality.
>> >>> nan == nan
> 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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