[Python-3000] Updated and simplified PEP 3141: A Type Hierarchy for Numbers

[Collin Winter]

On 5/17/07, Guido van Rossum <guido at python.org> wrote:
> On 5/17/07, Collin Winter <collinw at gmail.com> wrote:
> > ABCs can define concrete methods. These concrete methods provide
> > functionality that the child classes do not themselves provide.
>
> You seem to be misreading my intention here. ABCs serve two purposes:
> they are interface specifications, and they provide "default" or
> "mix-in" implementations of some of the methods they specify. The
> pseudo-inheritance enabled by the register() call uses only the
> specification part, and requires that the registered class implement
> all the specified methods itself. In order to benefit from the
> "mix-in" side of the ABC, you must subclass it directly.

I think I'm getting confused between the PEP and what you've said at
one of the various whiteboard sessions.