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From: Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>
Newsgroups: comp.lang.ada
Subject: Re: Is T an ancestor of T?
Date: Wed, 20 Oct 2004 14:02:52 +0000 (UTC)
Organization: GMUGHDU
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Christoph Karl Walter Grein <AdaMagica@web.de> wrote:
: From: Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>
: 
:> I still don't know whether or not a type is an ancestor of itself,
:> given that it is a descendant of itself.
: 
: Looking into RM Index for ancestor, you'll find the reference to RM 3.4.1(10) with the definition of ancestor and descendant:

Yes, descendant seem clearly defined in this paragraph. However,
"The ultimate ancestor of a type is the
 ancestor of the type that is not a descendant of any other type."

(In the original example, there was a new tagged private type T
and an aggregate T'(T with n => ) which is o.K. by GNAT, not o.K.
by Object Ada. When T is derive via new from some tagged T0,
both compilers agree again.)

What is "any other type"? Likely it means any type other than the
descendant (which can be a descendant of itself according to the
first sentence of 3.4.1(10))? So by the descendant wording,

   T0 ==> {T0, T1, T1', T2, ...}.

Which of T0, ... is not a descendant of any other type?
And is an ultimate ancestor listed in the line above when ancestor
is "the reverse" of descendant?
That is too tricky for me :-)

-- Georg