When is min(a, b) != min(b, a)?

[Mark Dickinson]

On Jan 24, 7:09 pm, Steven D'Aprano <st... at REMOVE-THIS-
cybersource.com.au> wrote:
> I'm having a lot of trouble finding the canonical IEEE-754 standard, so
> I'm forced to judge by implementations and third party accounts. For
> example, this is what IBM says:

There's a recent draft of IEEE 754r (the upcoming revision to IEEE
754) at

http://www.validlab.com/754R/drafts/archive/2007-10-05.pdf

Sections 5.11 and 5.3.1 deal with comparison predicates and the maxnum/
minnum operations, respectively.

One of the problems here is that Python's == operator is used for two
different purposes:  first, for numeric comparisons (where in some
sense it's semi-reasonable for NaN == NaN to return False, or raise an
exception), and second, for structural operations like checking set or
dict membership.  Most of the time there's not too much conflict here,
but while I fully expect 2 == Decimal('2.0') to return True, it still
occasionally feels funny to me that I can't have Decimal("2.0") and
the integer 2 be different keys in a dict:  certainly they're
numerically equal, but they're still fundamentally different objects,
dammit!

Any change to Python that made == and != checks involving NaNs raise
an exception would have to consider the consequences for set, dict,
list membership testing.

Mark


and if Python had separate operators for these two purposes it
wouldn't be Python any more.


Mark