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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Problem with Booch iterators
Date: 14 Nov 2002 06:44:28 +0000
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mheaney@on2.com (Matthew Heaney) writes:

> 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.

But then, given a non-STL mindset, why would you want to? In the STL,
iterators are related to the notion of pointer; in the BCs, they
aren't (to anything like the same extent). In the original BCs,
iterators were limited too, so you had to have a concrete iterator per
concrete container type .. well, actually, for half of them (the
leaves were foo_Iterator, foo_Non_Iterator).

I would like to know just how many real C++ programs use iteration
ranges other than begin() .. end().

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

Well, in Charles I guess that Iterator'Class is a pretty meaningless
concept.