Re: Discriminant and type extensions

[Robert A Duff <bobduff@shell01.TheWorld.com>]

"Hibou57 (Yannick Duch�ne)" <yannick_duchene@yahoo.fr> writes:

> I was looking at two of my generic packages, fully functionals, that
> is not the trouble, but not expressive enough IMHO.
>
> The lack, from my point of view, is in the way a type can be extended
> from a another type with discriminants.
>
> What I mean : I've got a type in a package, a tagged type with
> discriminants. Then a second package extends this type, but the
> discriminants from the extended type does not appears in the extension
> declaration. When I want to instantiate the type (the extended one), I
> obviously have to provide the actuals for these discriminants (the
> ones coming from the type which was extended).
>
> What do you think about it ?
>
> Do you think it would be a good proposal to allow the discriminant to
> be explicitly recalled in an extension declaration ? (just to be more
> explicit and expressive)

I'm not sure exactly what you mean, but you can do things like this:

    type T (D : Positive) is tagged ...
    type T2 (D : Positive; D2 : Boolean) is new T(D => D);
    type T3 is new T(D => 1_000_000);
    type T4 (D2 : Boolean) is new T(D => 1_000_000);

- Bob