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From: tmoran@acm.org
Newsgroups: comp.lang.ada
Subject: Re: Variant records..
References: <e8f9995c.0402151451.5bbe03de@posting.google.com>
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Date: Mon, 16 Feb 2004 23:17:10 GMT
Xref: archiver1.google.com comp.lang.ada:5616
Date: 2004-02-16T23:17:10+00:00
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How about instead:
   type Vehicle_Type is abstract tagged null record;

   procedure Set_Speed(This : in out Vehicle_Type; S : in Speeds);
   function State_Of(This : Vehicle_Type) return States;

   type Vehicle_Power is (MANUAL, AUTOMATIC);

   type Car is new Vehicle_Type(Power : Vehicle_Power) with null record;
   procedure Shift_Gears(This : in out Car;
                         New_Gear : Positive);

   type Man is new Vehicle_Type with null record;
   ...

   Audi : CAR(Power => MANUAL);
   John : Man;
   ...
   Set_Speed(Audi, 65);
   Set_Speed(John, 6);
   Shift_Gears(Audi, New_Gear=>2);
   Shift_Gears(John, New_Gear=>2);  -- illegal