Re: Problem with Booch iterators

[mheaney@on2.com (Matthew Heaney)]

porton@ex-code.com (Victor Porton) wrote in message news:<3dcd00f3$0$307$bed64819@news.gradwell.net>...
> There are a serious misdesign of Booch iterators:
> 
> Declaring a record component of type Iterator'Class,
> I get error "unconstrained subtype in component declaration".

You have identified what I consider to be a serious flaw in the Booch
Components.  The problem is that record components must be definite;
unconstrained subtypes must be given a constraint.

The BC iterator factory functions return Iterator'Class, which is
indefinite.  You cannot use T'Class as a record component.

The Charles library was optimized for flexibility, and therefore the
iterators in Charles are all "definite" subtypes, which means you can
use them as record components (or array components, or container
elements).

 
> So for every non-abstract collection type, a concrete iterator
> type should be visibly declared. 

Yes.

> It also suggests that types of
> arguments of subrountines should be changed from Iterator'Class
> to the appropriate concrete types.

Yes.