Re: Can a child access private types of its parent?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Tue, 21 Jul 2009 04:42:36 -0700 (PDT), vlc wrote:

> in the following code extract, I try to access a private variable I
> (line 09) in the Parent's type P from Child (in function Get, line
> 23):
> 
> 01  with Ada.Integer_Text_Io; use Ada.Integer_Text_Io;
> 02
> 03  procedure Main is
> 04
> 05  package Parent is
> 06        type P is tagged private;
> 07     private
> 08        type P is tagged record
> 09           I : integer := 5;
> 10        end record;
> 11     end Parent;
> 12
> 13     package Child is
> 14        type C is new Parent.P with private;
> 15        function Get (This : C) return integer;
> 16     private
> 17        type C is new Parent.P with null record;
> 18     end Child;
> 19
> 20     package body Child is
> 21        function Get (This : C) return integer is
> 22        begin
> 23           return This.I;
> 24        end Get;
> 25     end Child;
> 26
> 27     Var : Child.C;

> Is there a way to inherit private types from a Parent to its child?

Child is not a child of Parent. Move Parent out of Main to the library
level and make Child also a library package named Parent.Child. I.e.

package Parent is
   type P is tagged private;
private
   type P is tagged record
      I : integer := 5;
   end record;
end Parent;

package Parent.Child is
   type C is new Parent.P with private;
   function Get (This : C) return integer;
private
   type C is new Parent.P with null record;
end Parent.Child;

package body Parent.Child is
   function Get (This : C) return integer is
   begin
      return This.I;
   end Get;
end Parent.Child;

with Ada.Integer_Text_Io; use Ada.Integer_Text_Io;
with Parent.Child;

procedure Main is
   Var : Parent.Child.C;
begin
   Put (Var.Get);
end Main;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de