Re: Can Ada95 features replace the use of Ada 83 Varient records?

[Matthew Heaney <matthew_heaney@acm.org>]

"Mark" <mark@lourow.demon.co.uk> writes:

> -- 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?

Here you go:


package Test is

   type Large_Data_Type is new Integer;     -- large record normally

   type Rec_Type is tagged null record;

   type Changed_Rec_Type is
     new Rec_Type with record
        Data : Large_Data_Type;
     end record;

   function Get return Rec_Type'Class;

end Test;


package body Test is

   Large_Data : Large_Data_Type := 1;

   function Get return Rec_Type'Class is

      Outside_Event : Boolean := false;

   begin
      case Outside_Event is
         when True =>
            return Changed_Rec_Type'(Data => Large_Data);

         when False =>
            return Rec_Type'(null record);

      end case;
   end Get;

end Test;