[Python-3000] Wither PEP 335 (Overloadable Boolean Operators)? (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Sat May 26 03:41:29 CEST 2007

Jim Jewett wrote:

It currently says that not can return NotImplemented, which falls back to the current semantics.

I'm not sure why I put that there. As you observe, it's not necessary, since you can always get the default semantics simply by not defining the method.

An experiment suggests that the existing unary operator methods don't special-case NotImplemented, so I'll remove that part.

It does not yet say what will happen for objects that return something else outside of {True, False},

There's nothing to say -- whatever you return is the result. That's the whole point of making it overloadable.

Is that OK, because "not not X" should now be spelled "bool(x)", and you haven't allowed the overriding of bool?

Yes, I would say that 'not not x' should indeed be spelled bool(x), if that's what you intend it to mean.

Whether bool should be overloadable is outside the scope of this PEP. But if it is overloadable, I would recommend that it not be allowed to return anything other than a boolean.

-- Greg

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