Re: Suggestion for Ada 200x - Interface inheritance

[wojtek@power.com.pl (Wojtek Narczynski)]

Robert A Duff <bobduff@shell01.TheWorld.com> wrote in message news:<wccznlcm226.fsf@shell01.TheWorld.com>...

> More than one interface can be inherited.  That sounds like "multiple
> inheritance" to me.  Java interface inheritance is just like C++ muliple
> inheritance, with the restriction that you can't inherit record
> components and procedure bodies.

Usually you implement the interface. This likely comes from the
Objective-C ground, where you have 'protocols' (different name, same
role, said to be inspiration for Java interfaces). It's pretty natural
that you implement a protocol, not inherit a protocol. In the same
sense an interface/protocol can implement another interface/protocol.

The question boils down to wether an interface is an ancestor of the
type which implements (/inherits?) it. I think it is not, and thus
prefer to talk about implementing the interface not inheriting it. For
examle the USB interface is not an ancestor of my PC.

> > But I'll welcome whatever comes out, because the inability to create
> > heterogenous collections just plain sucks.
> 
> What do you mean by that?  You can pass class-wide types to generic
> collection packages, and that's heterogeneous.  I guess you mean you
> can't do what interface'Class allows...

I meant the situation where I needed to store objects from two
libraries I could not put a common ancestor above. But I admit it is
not the usual case.

> > By the way, is there an AI for the second thing Ada could learn from
> > Java, that is 'throws' clause?
> 
> I think there's one about pre- and post-conditions, which is somewhat
> related.

Yeah. Pre- and post-conditions are easier, I guess, because they can't
break current code, while the introduction of 'throws' ('raises'?),
without some trick, would.

Regards,
Wojtek