From: danmcleran@hotmail.com
Subject: Re: Possible Ada deficiency?
Date: 1 Jan 2005 15:28:10 -0800
Date: 2005-01-01T15:28:10-08:00 [thread overview]
Message-ID: <1104622090.271236.286730@c13g2000cwb.googlegroups.com> (raw)
In-Reply-To: <p42feqrui3cs.n1bi6hz47hux$.dlg@40tude.net>
Here's a different way to illustrate this problem. If I want to extend
a type, I can do this with a non-child package. But, if I make the
package containing the extended type a child package, I then have
access to all of the private area as well. So, one can extend a type
with or without access to the private area, depending on whether one
makes the packages containing the derived type a child package or not.
In my example, notice that the derived type in the child package can
change the private area, whereas the derived type in the non-child
package cannot.
Consider these files (Main.adb is the test program):
--Some_Package.ads
package Some_Package is
type Secret_Type is tagged private;
procedure Print_Secret_Value (Value : in out Secret_Type'Class);
private
type Secret_Type is tagged record
Secret_Value : Integer := 0;
end record;
end Some_Package;
--Some_Package.adb
with Ada.Text_IO;
package body Some_Package is
procedure Print_Secret_Value (Value : in out Secret_Type'Class) is
begin
Ada.Text_IO.Put_Line (Item => "Secret value = " &
Integer'Image(Value.Secret_Value));
end Print_Secret_Value;
end Some_Package;
--Some_Package.Child_Package.ads
package Some_Package.Child_Package is
type Some_Child_Type is new Secret_Type with null record;
procedure Badness (
Child : in out Some_Child_Type;
New_Value : in Integer);
end Some_Package.Child_Package;
--Some_Package.Child_Package.adb
package body Some_Package.Child_Package is
procedure Badness (
Child : in out Some_Child_Type;
New_Value : in Integer) is
begin
Child.Secret_Value := New_Value;
end Badness;
end Some_Package.Child_Package;
--Non_Child_Package.ads
with Some_Package;
package Non_Child_Package is
type Derived_Type is new Some_Package.Secret_Type with null record;
procedure Badness (
Derived : in out Derived_Type;
New_Value : in Integer);
end Non_Child_Package;
--Non_Child_Package.adb
package body Non_Child_Package is
procedure Badness (
Derived : in out Derived_Type;
New_Value : in Integer) is
begin
--Derived.Secret_Value := New_Value;--won't compile
null;
end Badness;
end Non_Child_Package;
--Main.adb
with Some_Package;
with Some_Package.Child_Package;
with Non_Child_Package;
procedure Main is
Child_Value : Some_Package.Child_Package.Some_Child_Type;
Non_Child : Non_Child_Package.Derived_Type;
begin
Some_Package.Print_Secret_Value (Value => Child_Value);
Some_Package.Print_Secret_Value (Value => Non_Child);
Some_Package.Child_Package.Badness (Child => Child_Value, New_Value
=> 100);
Non_Child_Package.Badness (Derived => Non_Child, New_Value => 100);
Some_Package.Print_Secret_Value (Value => Child_Value);
Some_Package.Print_Secret_Value (Value => Non_Child);
end Main;
next prev parent reply other threads:[~2005-01-01 23:28 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-31 18:15 Possible Ada deficiency? danmcleran
2004-12-31 19:12 ` Jeffrey Carter
2005-01-01 1:52 ` danmcleran
2005-01-01 2:37 ` Jeffrey Carter
2005-01-01 2:02 ` danmcleran
2005-01-01 14:11 ` Martin Krischik
2005-01-01 15:27 ` danmcleran
2005-01-02 17:49 ` Martin Krischik
2005-01-01 15:30 ` Stephen Leake
2005-01-01 15:57 ` danmcleran
2005-01-03 23:37 ` Randy Brukardt
2005-01-07 17:26 ` Nick Roberts
2005-01-07 18:26 ` danmcleran
2005-01-07 21:32 ` Randy Brukardt
2005-01-08 3:56 ` Nick Roberts
2005-01-08 18:15 ` Robert A Duff
2005-01-08 19:11 ` Jeffrey Carter
2005-01-08 20:03 ` Robert A Duff
2005-01-09 3:40 ` Jeffrey Carter
2005-01-09 17:30 ` Robert A Duff
2005-01-09 19:24 ` Jeffrey Carter
2005-01-09 21:56 ` Nick Roberts
2005-01-10 13:47 ` Dmitry A. Kazakov
2005-01-10 16:46 ` Duncan Sands
2005-01-10 17:58 ` Pascal Obry
2005-01-10 18:45 ` Dmitry A. Kazakov
2005-01-10 19:44 ` Pascal Obry
2005-01-11 10:05 ` Dmitry A. Kazakov
2005-01-11 7:24 ` Vinzent 'Gadget' Hoefler
2005-01-11 9:48 ` Dmitry A. Kazakov
2005-01-11 13:57 ` Vinzent 'Gadget' Hoefler
2005-01-11 21:52 ` Robert A Duff
2005-01-12 11:22 ` Dmitry A. Kazakov
2005-01-09 17:23 ` danmcleran
2005-01-09 17:46 ` Robert A Duff
2005-01-10 3:05 ` danmcleran
2005-01-09 18:41 ` Nick Roberts
2005-01-09 19:06 ` Martin Krischik
2005-01-09 20:10 ` Robert A Duff
2005-01-09 20:15 ` Robert A Duff
2005-01-11 14:13 ` Possible Ada deficiency? (goto) Peter Hermann
2005-01-11 14:54 ` Nick Roberts
2005-01-11 22:15 ` Robert A Duff
2005-01-12 10:17 ` Peter Hermann
2005-01-15 17:34 ` Robert A Duff
2005-01-15 17:58 ` Dmitry A. Kazakov
2005-01-15 19:34 ` Robert A Duff
2005-01-10 20:15 ` Possible Ada deficiency? Randy Brukardt
2005-01-10 21:51 ` Robert A Duff
2005-01-11 20:23 ` Randy Brukardt
2005-01-11 21:24 ` Robert A Duff
2005-01-12 19:57 ` Randy Brukardt
2005-01-02 15:51 ` Adrian Hoe
2005-01-04 16:06 ` Peter Hermann
2005-01-01 23:36 ` tmoran
2005-01-02 3:38 ` danmcleran
2004-12-31 19:16 ` Martin Dowie
2005-01-01 2:32 ` Jeffrey Carter
2004-12-31 23:23 ` Nick Roberts
2005-01-01 1:56 ` danmcleran
2005-01-01 11:43 ` Dmitry A. Kazakov
2005-01-01 15:46 ` danmcleran
2005-01-01 17:58 ` Larry Kilgallen
2005-01-01 19:43 ` danmcleran
2005-01-02 0:36 ` Ed Falis
2005-01-02 3:36 ` danmcleran
2005-01-02 15:53 ` Ed Falis
2005-01-07 18:31 ` danmcleran
2005-01-07 18:44 ` Pascal Obry
2005-01-07 19:29 ` danmcleran
2005-01-07 21:28 ` Pascal Obry
2005-01-01 23:28 ` danmcleran [this message]
2005-01-02 10:26 ` Dmitry A. Kazakov
2005-01-02 15:51 ` danmcleran
2005-01-03 23:48 ` Randy Brukardt
2005-01-01 14:06 ` Martin Krischik
2005-01-01 15:53 ` danmcleran
2005-01-07 21:33 ` Robert A Duff
2005-01-09 17:15 ` danmcleran
2005-01-09 17:38 ` Robert A Duff
2005-01-10 3:16 ` danmcleran
2005-01-09 18:41 ` Martin Dowie
2005-01-10 3:18 ` danmcleran
2005-01-10 20:32 ` Randy Brukardt
2005-01-10 21:42 ` danmcleran
2005-01-10 21:36 ` Robert A Duff
2005-01-10 21:44 ` danmcleran
2005-01-09 19:01 ` Jeffrey Carter
2005-01-10 3:20 ` danmcleran
2005-01-10 22:16 ` Robert A Duff
2005-01-10 22:29 ` danmcleran
2005-01-11 20:12 ` Georg Bauhaus
2005-01-11 20:30 ` danmcleran
2005-01-11 21:44 ` Robert A Duff
2005-01-11 0:06 ` Jeffrey Carter
2005-01-11 0:46 ` Robert A Duff
2005-01-11 20:37 ` danmcleran
2005-01-11 21:08 ` Robert A Duff
2005-01-17 4:40 ` Tucker
2005-01-18 13:46 ` danmcleran
2005-01-18 21:29 ` Nick Roberts
2005-01-24 17:23 ` danmcleran
-- strict thread matches above, loose matches on Subject: below --
2004-12-31 19:06 danmcleran
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