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From: "Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org>
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Newsgroups: comp.lang.ada
Subject: Re: How do you bitwise operations in Ada '83 and '95
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Date: 2006-07-18T19:21:38+00:00
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In Ada 83, you use packed arrays of Boolean or call a small C or 
assembler operation. In Ada 95, in addition to this, you can use modular 
types.

function "and" (Left : Integer; Right : Integer) return Integer;
-- Returns the bitwise logical and of Left and Right.

-- Ada 83:
function "and" (Left : Integer; Right : Integer) return Integer is
    type Bit_Set is array (1 .. Integer'Size) of Boolean;
    pragma Pack (Bit_Set);

    function To_Bit is new Unchecked_Conversion
       (Source => Integer, Target => Bit_Set);
    function To_Integer is new Unchecked_Conversion
       (Source => Bit_Set, Target => Integer);

    LB : constant Bit_Set := To_Bit (Left);
    RB : constant Bit_Set := To_Bit (Right);
begin -- "and"
    return To_Integer (LB and RB);
end "and";

Note the the language does not define whether LB (LB'First) is the LSB 
or MSB of Left.

-- Ada 95:
function "and" (Left : Integer; Right : Integer) return Integer is
    type Mod_Int is mod 2 ** Integer'Size;

    function To_Mod is new Ada.Unchecked_Conversion
       (Source => Integer, Target => Mod_Int);
    funtion To_Integer is new Ada.Unchecked_Conversion
       (Source => Mod_Int, Target => Integer);

    LM : constant Mod_Int := To_Mod (Left);
    RM : constant Mod_Int := To_Mod (Right);
begin -- "and"
    return To_Integer (LM and RM);
end "and";

-- 
Jeff Carter
"I'm a lumberjack and I'm OK."
Monty Python's Flying Circus
54