From: Dave Thomas <Dave@...>
Date: 2002-02-07T00:18:10+09:00
Subject: Re: Subclassing vs Subtyping (partly OOP vs FP)

Robert Feldt <feldt@ce.chalmers.se> writes:

> > 1. It could check that classes it was mixed in to defined the methods
> >    it needed.
> > 
> Minor quirk: I often write includes on the top so needed methods not yet
> defined?!

I _think_ you can hook that, only performing the test when the class
is added to the parent.

...

> >   class BTreeBag
> >     implements BagProtocol

> Sure, doesn't sound too hairy. Might be some conflicts with a truly
> dynamic philosophy (I want to add the needed methods later etc) but maybe
> not a problem in practice.

Exactly - but it's available for use when you want.

I'm thinking more and more that a way of documenting a class's
fundamental methods would be useful. For example, you want to
overwrite IO so that output goes to an in-memory buffer. Which methods
do you have to change. Certainly #write. But what about #putc? Is
#putc implemented in terms of #write? No way to know unless you read
the C source code. Similarly for Arrays. Is overriding [] and []=
enough? (No :).

Having ways of explicitly listing a protocol seems to be good sense,
if only from a documentation perspective.


Dave