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Date: Sat, 29 Sep 2012 19:34:09 +0200
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: highest bit, statically determined
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Date: 2012-09-29T19:34:09+02:00
List-Id: <comp.lang.ada>

Is there a shorter/better way of having the compiler
find the highest bit = 1 in a static numeric constant?

If N is such a constant, e.g. Some_Type'Last where
Some_Type'Size = 8 and its bound are static, then

    Highest_Bit_In_Octet : constant :=
      Natural'Max
      (8 * Boolean'Pos (N / 2**7 > 0),
       Natural'Max
       (7 * Boolean'Pos (N / 2**6 > 0),
        Natural'Max
        (6 * Boolean'Pos (N / 2**5 > 0),
         Natural'Max
         (5 * Boolean'Pos (N / 2**4 > 0),
          Natural'Max
          (4 * Boolean'Pos (N / 2**3 > 0),
           Natural'Max
           (3 * Boolean'Pos (N / 2**2 > 0),
            Natural'Max
            (2 * Boolean'Pos (N / 2**1 > 0),
             Natural'Max
             (1 * Boolean'Pos (N / 2**0 > 0), 0))))))));