"Jeffrey Carter" <spam@spam.com> a �crit dans le message de news:8sQmc.11414$V97.6807@newsread1.news.pas.earthlink.net...
> Jean-Pierre Rosen wrote:
> >
> > But you don't depend logically on something that you don't with. With
> > tagged types, you are really calling an implementation (in another
> > package) of something that you depend on - which is defined in a
> > package that you have withed.
>
> To my way of thinking, you depend on any types you may have objects of
> and anything you may invoke. A derived type is not the same type as its
> parent, nor are its operations the same as its parent's operations.
> Since type extension is a form of type derivation, I apply the same
> rules to type extension that I did to type derivation in Ada 83: the
> parent must be either a predefined type, or a type declared in the same
> declarative region as the child. Anything else quickly becomes unreadable.
>
But tagged types (OOP actually) is just about that: being able to add types later, without requiring recompiling existing modules
that use the class. I understand that you may not like that; in this case, just don't use tagged types. It was a very deliberate
decision to prevent tagged types from invading the whole language, precisely for this reason: they have no effect on people who
don't use them.

-- 
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           J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr