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From: Shark8 <onewingedshark@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Preventing type extensions
Date: Thu, 16 Sep 2010 17:16:52 -0700 (PDT)
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> Final classes make no sense. I am glad that at least this was not borrowed
> by Ada ... yet.


I agree; final classes are a bad idea -- Unless the object's behavior
is perfect and there can [in no way] be a changed requirement... which
almost never happens. There have been times where I've had to 'extend'
a final Java class by embedding it into another class and writing all
the methods as passthroughs except for the ones I needed to introduce
some [usually slightly] different behavior.

On the original poster's topic; is there anything from doing something
like:
Package Some_Object_Package is
  Type Object-Type is private;
  -- Elementery functions.
private
 Type Object-Type is tagged null record;
end package Some_Object_Package;

Sure, a child-package could be introduced to extend the object, but
its specification cannot rely on anything not publicly visible in its
parent's specification... meaning that the public portion of the
object cannot expose that it is a tagged record. Right?