Re: access on function returning a class wide type

["James S. Rogers" <jimmaureenrogers@worldnet.att.net>]

"alex" <xela@netcourrier.com> wrote in message
news:20021119-223832-295143@foorum.com...
>
> Is there a "workaround/trick" to implement this kind of think.
>
> package A is
>    type A_T is abstract tagged null record;
>    function Fa return A_T is abstract;
>    type Fa_Ptr is access function return A_T'Class;
> end A;
>
> with A;
> package B is
>   type B_T is new A.A_T with null record ;
>   function Fa return B_T;
> end B;
>
> package body B is
>   function Fa return B_T is
>   begin return (A.A_T with null record);
>   end Fa;
> end B;
>
> with A,B;
> procedure Test is
>    Ptr : A.Fa_Ptr := B.Fa'access; -- error :  LRM:8.6(28)
> begin null;
> end Test;
>
> The compiler is expecting a function returning a A_T'Class, ok I
understand.
> But, B_T is in the A_T'Class!

B_T is in the A_T'Class but a function returning B_T does not return a
class-wide type. You have defined Fa_Ptr to be an access type to a
function returning a class-wide type rooted in type A_T.

Another problem you have is that you are trying to return an instance
of an abstract type. You cannot create an instance of an abstract type.

Jim Rogers