Re: Indirect visibility of private part in child packages

["Hibou57 (Yannick Duchêne)" <yannick_duchene@yahoo.fr>]

Bonjour Ludovic, and thanks for your reply :)

On 4 juin, 09:50, Ludovic Brenta <ludo...@ludovic-brenta.org> wrote:
> Maybe you can solve your problem like this:
>
> package body P1.P3 is
>    procedure A_Primitive (Item : out T3_Type) is
>    begin
>       T1_Type (Item).Low_Level_Data := ...;
>    end A_Primitive;
> end P1.P3;

I've just tried it, and it does not work better. The compiler
complains there are not selector Low_Level_Data for T1_Type.


> I am undecided whether the compiler is correct or wrong about the
> visibility of Low_Level_Data. On the one hand, P1.P3 cannot see the
> full declaration of T2_Type; on the other hand, it can see that
> T2_Type publicly inherits from T1_Type and can also see the full
> declaration of T1_Type.
This is exactly the same think in my mind. Perhaps the semantic is
ambigous here.

> It seems that the public (partial) view of T2_Type hides the full
> declaration of T1_Type. So, I think my solution would work by removing
> T2_Type out of the way.

T2_Type is required ;) The purpose is to have T2_Type and T3_Type, and
may be later some others, beside of each other.

> Another solution, which enforces encapsulation better, would be:
>
> package P1 is
>    type T1_Type is tagged private;
> private
>    type Some_Type is ...;
>    type T1_Type is tagged record
>      Low_Level_Data : Some_Type;
>    end record;
>    procedure Set (Item : out T1_Type; Data : in Some_Type);
> end P1;
>
> package body P1.P3 is
>    procedure A_Primitive (Item : out T3_Type) is
>    begin
>       Set (Item, Data => ...); -- OK, calls inherited primitive
> operation
>    end A_Primitive;
> end P1.P3;
>
> HTH

I will try it soon and tell about the result. But at first sight, I
think that the compiler gonna complain that Set is a primitive of
T1_Type and thus that it must be defined in the public part. Further
more, I think Set would habe to be redefined for each T2_Type, T3_Type
and etc.

Will try and tell later

Have a nice day