Re: generic formal primitive [dispatching] operation

[Damien Carbonne <damien.carbonne@free.fr>]

Robert A Duff a �crit :

> Damien Carbonne <damien.carbonne@free.fr> writes:
>
> > I would like to create a generic package that has, as formal parameters,
> > a tagged type and some primitive dispatching operations on that type.
>
> Try using a generic formal derived type.  Declare the root type outside
> the generic, with the primitive you want, and then declare a generic
> formal type derived from that.
>

As I explained in my answer to Thomas Quinot, I would like to avoid this
solution, because it is a bit more rigid than what
I expect. But if what I expect is impossible, I will come back to it.

>
> > 1) How is it possible to define a formal primitive operation on a tagged
> > type that is:
> >    a) non dispatching (Root'Class ??)
>
> Primitive = dispatching (for tagged types).  Class-wide types are not
> primitive.
>
> >    b) dispatching
>
> See above.
>
> > 2) In the case of class-wide operations, is there any difference between
> > primitive and non primitive
> >    operations ? (I would say no ?)
>
> A class-wide operation is *not* primitive.
>
> - Bob

Sorry, I thought "primitivity" was only related to declarative region
+ freezing rules.
But it is in fact more restricted.

Is the following example correctly labelled ?
package P is
   type T is tagged null record;
   procedure Primitive(Obj : T);
   procedure Class_Wide(Obj : T'Class);
end P;

with P; use P;
package O is
   procedure What_Is_Its_Category(Obj : T);
   procedure Again_Class_Wide(Obj ; T'Class);
end O;


Can we consider that in the following declarations:
generic
   type Root is tagged private;
   with procedure P1(This : access Root);
   with procedure P2(This : access Root'Class);


1) P1 is primitive (that is dispatching). Root can be derived and P1
redefined. (It seems to be the case in
   the example I put in my answer to T.Quinot)
2) P2 is class-wide.

If this is true, my problem is, how is it possible to make the initial
example work, keeping the same spec (just changing the body).

Thanks for clarifications.

Damien.