[Python-3000] Special methods and interface-based type system

[Bill Janssen]

> Saying the same thing in another way, I see 'len' as a built-in
> *operation*. I'd hate to lose that. I can't say for sure whether you
> meant that or not, but 'def len(self): ...' certainly sounds like you
> want to demote it to an ordinary method. I'm strongly -1 on that.

OK, I can see that.  So the built-in function len() and its cousins
should be thought of as special Python syntax.  I see no real reason
to remove that; if "<" just invokes a standard method
"orderable.lessthan", the built-in len can just invoke
"container.len".  But foo.len() would also be available for use.

> I didn't want these special operations to use ordinary
> method names, because then pre-existing classes, or classes written by
> users without an encyclopedic memory for all the special methods,
> would be liable to accidentally define operations they didn't mean to
> implement, with possibly disastrous consequences.

Hmmm.  This seems kind of a weak rationale to me, but OK.

Bill