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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Indirect visibility of private part in child packages
Date: Thu, 4 Jun 2009 00:50:10 -0700 (PDT)
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Date: 2009-06-04T00:50:10-07:00
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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 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.

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.

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

--
Ludovic Brenta.