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From: Hyman Rosen <hyrosen@mail.com>
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Newsgroups: comp.lang.ada
Subject: Re: Question about OO programming in Ada
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Date: Tue, 09 Dec 2003 04:52:31 GMT
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Date: 2003-12-09T04:52:31+00:00
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Chad Bremmon wrote:
> The state of the boolean is not kept in a variable.  The code I wrote 
> actually changes the register to turn the light on and off.  A boolean 
> is not necessary to keep track of the light.  Either the damn light is 
> on or off.

I quote from your article:

     type Object is tagged record
           Address : System.Address;
           Mask    : Opsys.Unsignedshort;
           Is_On   : Boolean := False;
         end record;

     procedure Turn_Off (This : in out Object) is
         Register : Opsys.Unsignedshort;
         for Register'Address use This.Address;
     begin
         if This.Is_On then
             Register := Register xor This.Mask;
         end if;
     end Turn_Off;
     procedure Turn_On (This : in out Object) is
         Register : Opsys.Unsignedshort;
         for Register'Address use This.Address;
     begin
         if not This.Is_On then
             Register := Register xor This.Mask;
         end if;
     end Turn_On;

What changes Is_On?