Problem with Booch iterators

[porton@ex-code.com (Victor Porton)]

There are a serious misdesign of Booch iterators:

Declaring a record component of type Iterator'Class,
I get error "unconstrained subtype in component declaration".

So for every non-abstract collection type, a concrete iterator
type should be visibly declared. It also suggests that types of
arguments of subrountines should be changed from Iterator'Class
to the appropriate concrete types.

Simon, why you've used Iterator'Class everywhere?