[Python-3000] PEP 3100 Comments

[Phillip J. Eby]

At 09:35 AM 5/9/2006 -0700, Bill Janssen wrote:
>Phillip Eby writes:
> > In Haskell, interfaces are defined using "typeclasses".  A typeclass is
> > basically a collection of generic functions.  For example, you could 
> define
> > ...
> > Further, Haskell has a concept of "typeclass instances" which basically
> > give you adaptation.  For example, suppose I have some generic functions
>
>Thanks, Phillip.  That's essentially what I'm talking about with CL
>mixins, as well (though instead of typeclass instances you usually
>have mixin implementations which are "mixed" into the class which
>wishes to provide the interface, to give it the methods).

Unless this can be done by a third party, it's not at all the same 
thing.  Currently in Python for a third party to add a mixin, they would 
have to hack the class's __bases__, which I am not suggesting here at all.

In fact, it's pretty much the opposite of what I'm suggesting -- you 
shouldn't *have* to make such declarations, let alone monkeypatch a class's 
__bases__.


>That's what
>I think Py3K should be using, too, instead of "duck typing", which for
>some reason has come to be thought of (wrongly) as a "feature".

I don't see that discussion as being even remotely related to what I'm 
talking about, so please don't count my comments as being against duck 
typing or supporting its removal.

Indeed, I consider my suggestion to be support for *extending* duck typing, 
and a vote *against* typing by inheritance.  You seem to be very confused 
about what I said.