Re: Tagged types (beginner's question) !

[Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>]

Vincent DIEMUNSCH <"vincent.diemunsch"@edf.fr@NO.SPAM.PLEASE> writes:

> Hello,
> 
> I have a simple question concerning tagged types. Suppose that we have :
> 
>     type Rationnel is abstract new Ada.Finalization.Controlled with null
> record;
> 
>     type Fraction is new Rationnel with record
>           Num�rateur    : integer;
>           D�nominateur : positive;
>        end record;
> 
>     type Entier is new Fraction with null record;
> 
> First Question :
>     Can I override the primitive operation "Adjust" of the controlled
> type with the following :
>         procedure Adjust (F : in out Fraction'Class);
>     instead of :
>         procedure Adjust( F : in out Fraction);

No. This would be "overloading", not "overriding". Calls to Adjust on
an object of type Rationnel or Fraction made by the run-time system
will not dispatch to this procedure.

Adjust has a very specific meaning for Controlled types. Why do you
want to do this instead?

> Second question : How can Adjust (F : in out Fraction'Class) return
> an object of type Entier instead of Fraction ? 

Note that Adjust is a procedure, so it does not "return" anything. Not
clear what you really mean here.

Again, why do you want to do this? 

If you are trying to emulate C++ constructors (just a wild guess), try
defining:

function New_Entier (...) return Entier;

-- 
-- Stephe