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

[Bill Janssen]

> I had thought that you (Bill), (along with PJE) were assuming that the
> generic function or interface itself would serve to distinguish the
> namespace.  Instead of
> 
>     class A(object):
>         def magic_meth_foo(self, ...):
> 
> I would write
> 
>     class A(object):
>         defop foo.magic_meth(self, ...)
> 

There seem to be two justifications for "special" methods that have
been adduced (though I see no real justification for the name-mangling
scheme).  One is that they serve as a way of specifying which code
operators and their cousins, the "built-in" generic functions, call.
The other is that they somehow serve as connections to the underlying
VM implementation.  Now, I don't see why the connection to the
underlying VM implementation needs name-mangling -- it would be
reasonable just to define a distinguished module (call it, say, for
tradition's sake, "__VM__" :-), and put them in that module.

But there does need to be some way to connect operator syntax to code,
and we could talk about how to do that.  Defop is one solution; you
could also imagine an ABC for each operator, and classes which wish to
use that operator, or overload it, would inherit from that ABC and
re-define the methods.  The question is, would those methods, bound to
specific operators, be so pervasive and so common that their logical
method names would, if not mangled, occupy too much of the available
naming space?  Maybe.  I think it's a judgement call.

Bill