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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: bit operations on integers
Date: 1999/05/03
Message-ID: <m34slut6ur.fsf@mheaney.ni.net>#1/1
X-Deja-AN: 473567487
References: <7gkhr7$5kr$1@nnrp1.dejanews.com>
NNTP-Posting-Date: Mon, 03 May 1999 10:07:50 PDT
Newsgroups: comp.lang.ada
Date: 1999-05-03T00:00:00+00:00
List-Id: <comp.lang.ada>

phadreus@iname.com writes:

> How do I test, set, and clear individual bits in an integer
> in Ada 83?

Convert the object to an array of Booleans:

 type Integer_8 is range 0 .. 255;

 for Integer_8'Size use 8;


 type Boolean_Array is (Natural range <>) of Boolean;
 pragma Pack (Boolean_Array);

 subtype Boolean_Array_8 is Boolean_Array (0 .. 7);

 function To_Boolean_Array is 
   new Unchecked_Conversion (Integer_8, Boolean_Array_8);

 function To_Integer_8 is
   new Unchecked_Conversion (Boolean_Array_8, Integer_8);


 procedure Set_Bit (I : in out Integer_8; N : in Natural) is

    BA : Boolean_Array_8 := To_Boolean_Array (I);

 begin

    BA (N) := True;   -- BA (7 - N) on a big endian machine

    I := To_Integer_8 (BA);

  end Set_Bit;


  procedure Clear_Bit ...

  function Get_Bit ...


 declare
   I : Integer_8;
 begin

   Set_Bit (I, 2);