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From: 402450@cepsz.unizar.es (Jano)
Newsgroups: comp.lang.ada
Subject: Re: Problem with access types using Booch components.
Date: 12 Feb 2003 01:06:42 -0800
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Jano <402450@cepsz.unizar.es> wrote in message news:<MPG.18b39bca994daf55989693@News.CIS.DFN.DE>...
> En el mensaje <x7vsmuu7dn9.fsf@smaug.pushface.org>, simon@pushface.org 
> dice...
> 
> Hello,
> 
> > What compiler/version are you using?
> 
> I'm using Gnat 3.15p
> 
> > With GNAT 3.15p I get this to compile without complaint (and to run,
> > though it's not a thorough test!).
> 
> Mmm, I get it also to compile, it's only at runtime that I get the 
> Constraint_error exception raised, saying "tag check failed" or the like 
> (sorry, I'm not at work where I have the sources to quote it exactly)
> 
> > Note the 'Class ....
> 
> I've noted it. Really, I was following the example in the docs very 
> closely because I've just begun to try it.
> 
> Your example below it's exactly what I have, but I have it splitted 
> across some packages. I find it strange, specially because of the error 
> going away when I assign the access to a local container.
> 
> Uhm! I see now a difference. You are getting the iterator from CU, which 
> is the unit who contains the type Collection. In the example in the docs 
> (and in my program) I'm getting the Iterator from the top 
> abstract_container. I suppose dispatching takes care of this? But what 
> about the different behavior in my case when using the access or the 
> local container?

ARG! MY MEMORY FAULT ANOTHER TIME. I was taking the iterator from the
same package you are. So the problem remains equal.

Now I have the exact error wording:

CONSTRAINT_ERROR: bc-containers-collections.adb:93 tag check failed

> Thanks anyway, I'll try tomorrow to use the CU-level package...
> 
> > with Collection_Test_Support;
> > 
> > procedure Jano is
> > 
> >    use Collection_Test_Support;
> > 
> >    type CU_P is access all CU.Collection;
> > 
> >    C : aliased CU.Collection;
> >    CP : CU_P := C'Access;
> > 
> > begin
> > 
> >    declare
> >       It : Containers.Iterator'Class := CU.New_Iterator (CP.all);
> >    begin
> >       null;
> >    end;
> > 
> > end Jano;