[Python-3000] PEP 3100 Comments

[Phillip J. Eby]

At 10:12 AM 5/10/2006 -0700, Bill Janssen wrote:
> > >> this approach doesn't do anything beyond what Java does
> > >
> > >Actually, it does.  It lets you inherit behavior, as well as interfaces.
> >
> > It only lets you inherit behaviour to new subclasses
>
>Not that it matters, but...

Clearly it doesn't matter to *you*.  It does matter to me.


>Yes, that's right.  In systems like
>these, that's how you "add functionality to already existing classes";
>you mix them with the new functionality into a new type.

Which makes them inferior to existing adaptation systems for Python, which 
in turn are inferior to generic functions.

When I say that thing A is "inferior" to thing B, I mean that B can do 
whatever A can, but A cannot be used to do things that B can.  By that 
definition, using inheritance to denote behavior availability is markedly 
inferior to the other alternatives.