[Python-3000] Builtin iterator type

[Bill Janssen]

> Andrew Koenig wrote:
> > In other words, whether or not we choose to define a family of types that
> > stand for particular abilities, I think we should not use inheritance as the
> > mechanism for specifying that a particular class has a particular ability.
> > I don't know what the mechanism should be, but it shouldn't be inheritance.
> > 
> > Am I missing something?
> 
> It seems to me to be an excellent write-up of why using concrete classes for 
> interface definitions is potentially problematic.

Huh?  Andrew pointed to exactly one "drawback", the inability to
disassociate an inherent characteristic of a type, its "typeness"
(which he refers to as ability-signalling), from a type.  I hardly see
that as problematic.

Am *I* missing something?

Bill