Re: Proposal: Abstract types for OOC

[Michael van Acken <Michael.van.Acken@de.uu.net>]

Stewart Greenhill <greenhil@murdoch.edu.au> writes:

> At 08:17 PM 3/1/99 +0100, hartmut Goebel wrote:
> 
> >Conclusion
> >----------
> >
> >Requiering of explicit declaring a record type as abstract introduces a lot
> >of problems, be it logically, language consistency, extensability or
> >implementational (see mva's posting).

I think this is an exaggeration.  And actually I am in favour of an
explicit ABSTRACT flag for records, but I am not too fond of a rule
that says "a record marked as ABSTRACT must have at least one method
marked as ABSTRACT".

Since I am the one to extend the compiler, I prefer a more pragmatic
(and not philosophically) view on "abstractedness": a _record_ marked
with ABSTRACT cannot be instanciated, and a _method_ marked with
ABSTRACT must belong to a record marked with ABSTRACT, and must be
implemented in any extension that is not marked with ABSTRACT.

Please note that I am not talking about a record or method _being_
abstract, just about entities marked with ABSTRACT.

-- mva