[Cython] Bindings performance issue

[Robert Bradshaw]

On Thu, Jun 2, 2011 at 2:03 PM, mark florisson
<markflorisson88 at gmail.com> wrote:

>>>> If anyone is assigning a Cython function to an object and then using
>>>> it they're counting on the current non-binding behavior, and it will
>>>> break. The speed is probably a lesser issue, which is what benchmarks
>>>> are for.
>>>
>>> If you're binding functions to classes without expecting it to ever
>>> bind, you don't really have bitching rights when stuff breaks later
>>> on. You should have been using staticmethod() to begin with. And we
>>> never said that our functions would never bind :)
>>
>> No, you're assigning it to an object, counting on being able to call
>> it later on. E.g. the following is legal (though contrived in this
>> example):
>>
>> sage: class A:
>> ....:     pass
>> ....:
>> sage: a = A()
>> sage: a.foo = max
>> sage: a.foo([1,2,3])
>> 3
>>
>> If instead of len, it was one of our functions, then it would be bad
>> to suddenly change the semantics, because it could still run but
>> produce bad answers (e.g. if we had implemented max, suddenly a would
>> be included in the comparison). This is why I proposed raising an
>> explicit error as an intermediate step.
>>
>> If we don't promise anything, the contract is whatever the code does.
>> That's the problem with not having a specification (which would be
>> really nice, but is a lot of work).
>
> Functions on objects never get bound, they only get bound if they are
> on the class. So your code would still work with binding functions.

True. It would still break "A.foo = max" though. I'm not saying we
should support or encourage this, but lets break it hard before we
break it subtly.

- Robert