[Python-Dev] PyObject_RichCompareBool identity shortcut

[Greg Ewing]

Stephen J. Turnbull wrote:
> So what does the 1/0 that
> occurs in [1/x for x in range(-5, 6)] mean?  In what sense is it
> "equal to itself"?  How can something which is not a number be
> compared for numerical equality?

I would say it *can't* be compared for *numerical* equality.
It might make sense to compare it using some other notion of
equality.

One of the problems here, I think, is that Python only lets
you define one notion of equality for each type, and that
notion is the one that gets used when you compare collections
of that type. (Or at least it's supposed to, but the identity-
implies-equality shortcut that gets taken in some places
interferes with that.)

So if you're going to decide that it doesn't make sense to
compare undefined numeric quantities, then it doesn't make
sense to compare lists containing them either.

-- 
Greg