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From: Kirk Beitz <beitz@volkov.nosc.mil>
Subject: Re: Polymorphism question
Date: 1997/02/23
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Newsgroups: comp.lang.ada
Date: 1997-02-23T00:00:00+00:00
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Robert Oeckl <oeckl@pheno.physics.wisc.edu> writes:

> 
> I have problems to figure out, how Polymorphism works in Ada. I want to
> know if and how the following is possible in Ada:
> 
> Suppose I have an abstact type A. Now I have two (non-abstract)
> descendants B and C of A. Furthermore there is a descendant D of C. For
> A an abstract procedure P1 is defined and for B and C P1 is overloaded.
>
> I do also want to be able to call P1 with type D without explicitly
> defining P1 for D, so that the procedure as defined for type C is
> executed with type D.

well, you are out of luck.  you must define P1 for type D separately.  that
is the nature of the abstract definition of P1.

> Now I have a procedure P2 defined for type C. For type D I want to
> overload this procedure. But in the overloaded procedure I want make a
> call to P2 as defined for C, if possible without loosing the information
> that the object is actually of type D inside the called procedure.

actually, those of us whom english is a first language use the word "losing"
to describe what you're talking about.  but other than that, i don't see
what it is you're trying to solve.