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From: "Mark" <mark@lourow.demon.co.uk>
Subject: Can Ada95 features replace the use of Ada 83 Varient records?
Date: 1998/08/21
Message-ID: <01bdcd2f$a7da71f0$0f010180@nc84c>#1/1
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Date: 1998-08-21T00:00:00+00:00
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-- I'm new to Ada95 (Familar with 83) and thought that the use 
-- of varient records in Ada 83 can be replaced by Tagged types.

-- Is it possible to implement the following using Ada 95 features?

package Test is

   type Large_Data_Type is new Integer;     -- large record normally
   type Rec (Changed : Boolean := False) is
   record
      case Changed is
         when TRUE  => 
            Data : Large_Data_Type;
         when FALSE => 
            null;
      end case;
   end record;
   
   function Get return Rec;
   
end Test;



-- with Some_Other_Package;
package body Test is 

   Large_Data : Large_Data_Type := 1;
   
   function Get return Rec is

      Outside_Event : Boolean := false; 
--      Outside_Event : constant Boolean :=
Some_Other_Package.Event_Occured; 
   
   begin 
      case Outside_Event is
         when True =>
            return (
               Changed   => True,
               Data      => Large_Data);
         when False =>
            return (Changed => False);
      end case;
   end Get;
end Test;