From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,29b1b6650a74a211
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2002-11-13 11:39:24 PST
Path: archiver1.google.com!postnews1.google.com!not-for-mail
From: mheaney@on2.com (Matthew Heaney)
Newsgroups: comp.lang.ada
Subject: Re: Problem with Booch iterators
Date: 13 Nov 2002 11:39:23 -0800
Organization: http://groups.google.com/
Message-ID: <1ec946d1.0211131139.50f479e1@posting.google.com>
References: <3dcd00f3$0$307$bed64819@news.gradwell.net>
NNTP-Posting-Host: 66.162.65.162
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
X-Trace: posting.google.com 1037216364 8730 127.0.0.1 (13 Nov 2002 19:39:24
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: 13 Nov 2002 19:39:24 GMT
Xref: archiver1.google.com comp.lang.ada:30831
Date: 2002-11-13T19:39:24+00:00
List-Id: <comp.lang.ada>

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.