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Date: Wed, 3 Oct 2012 02:30:51 -0700 (PDT)
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Subject: Re: highest bit, statically determined
From: kalvink65@gmail.com
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Date: 2012-10-03T02:30:51-07:00
List-Id: <comp.lang.ada>

How about binary search algorithm with constant execution time:

Binary_Search_Highest_Bit_In_Octet_2012 : constant :=
      (if N > (2**4)-1 then -- determine upper or lower nibble
          -- upper nibble
          if N > (2**6)-1
            -- bits 7 and 6
            if N > (2**7)-1 then
                7
            else
                6
          else
            -- bits 5 and 4
            if N > (2**5)-1 then
                5
            else
                4
       else
          -- lower nibble
          if N > (2**2)-1 then
            -- bits 3 and 2
            if N > (2**3)-1 then
                3
            else
                2
          else
            -- bits 1 and 0
            if N > (2**1)-1 then
                1
            else
                0);

Disclaimer: I am not an Ada programmer, so this might not compile, but describes the idea anyway.

- Kalvin