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From: "Matthew Heaney" <mheaney@on2.com>
Newsgroups: comp.lang.ada
Subject: Re: 'withing' problem
Date: Fri, 9 Nov 2001 15:28:48 -0500
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Date: 2001-11-09T15:28:48-05:00
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"David Crocker" <dcrocker@imsltd.com> wrote in message
news:3be65f4c$0$237$ed9e5944@reading.news.pipex.net...
> OK, so if you think cross-dependency reflects bad design when the
> implementation language is Ada, can you tell me how you would redesign the
> Doctor/Patent/Insurer example in
> http://home.bluemarble.net/~jvolan/WithingProblem/FAQ.html ?

There is no withing problem.  One possible solution appears below.

John is confused, and I recommend you disregard his paper.

Use gnatchop to extract the sources below.

--STX
with Patients; use Patients;

package body Doctors is

   procedure Treat_Patient
     (Doctor : in out Doctor_Type;
      Patient : in out Root_Patient'Class) is

      P : Patient_Type'Class renames Patient_Type'Class (Patient);
   begin
      null;
   end;


   procedure Bill_Patient
     (Doctor : in out Doctor_Type;
      Patient : in out Root_Patient'Class) is

      P : Patient_Type'Class renames Patient_Type'Class (Patient);
   begin
      Pay_Doctor (P, Doctor);
   end;


end Doctors;
with Patients_Forward; use Patients_Forward;

package Doctors is

   type Doctor_Type is tagged limited null record;

   procedure Treat_Patient
     (Doctor : in out Doctor_Type;
      Patient : in out Root_Patient'Class);

   procedure Bill_Patient
     (Doctor : in out Doctor_Type;
      Patient : in out Root_Patient'Class);

end;
   with Doctors; use Doctors;

package body Patients is

   procedure Visit_Doctor
     (Patient : in out Patient_Type;
      Doctor  : in out Doctor_Type) is
   begin
      Treat_Patient (Doctor, P);
   end;

   procedure Pay_Doctor
     (Patient : in out Patient_Type;
      Doctor  : in out Doctor_Type) is
   begin
      null;
   end;

end Patients;
with Patients_Forward; use Patients_Forward;
with Doctors; use Doctors;

package Patients is

   type Patient_Type is new Root_Patient with null record;

   procedure Visit_Doctor
     (Patient : in out Patient_Type;
      Doctor  : in out Doctor_Type);

   procedure Pay_Doctor
     (Patient : in out Patient_Type;
      Doctor  : in out Doctor_Type);

end;
package Patients_Forward is

   type Root_Patient is abstract tagged limited null record;

end;