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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: APQ
Date: Fri, 17 Dec 2004 15:12:42 +0100
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Date: 2004-12-17T15:12:42+01:00
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On Fri, 17 Dec 2004 14:45:17 +1100, Brian May wrote:

>    type Root_Connection_Type is abstract new Ada.Finalization.Limited_Controlled with private;

If you are going to rework it, then derive it directly from an abstract
object used for reference counting. That would save one level of
indirection:

  type Root_Connection_Type is abstract new Object.Entity with private;

>    procedure Connect(C : in out Root_Connection_Type) is abstract;

This is 100% legal. Probably you have conflicting views.

>    procedure Connect(C : in out Root_Connection_Type; Same_As : Root_Connection_Type'Class) is abstract;

Are you going to clone connections between different DBs? The above looks
like an attempt to emulate multiple dispatch.!

It should be:

  procedure Connect
            (  C : in out Root_Connection_Type;
               Same_As : Root_Connection_Type   -- Same types required!
            )  is abstract;

However would be is pretty useless, when you have a class-wide object at
hand.

I suppose that the idea was to make a copy of a limited object. Then it
should better be:

  function Copy (C : Root_Connection_Type)
     return Root_Connection_Ptr is abstract;

This would allocate a copy and connect it to the same DB. Because reference
counting is intended you will need dynamic allocation anyway. The user will
of course do it all with handles:

   function Copy (C : Handle) return Handle is
      Clone_Ptr : Root_Connection_Type_Ptr := Copy (Ptr (C).all);
         -- This clones the object pointed by the handle, the reference
         -- count of the copy is initially 0
   begin
      return Ref (Clone_Ptr);
         -- Result is a handle, and the reference count is 1, now
   end Copy;

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