1 // -------------------------------------

     2 // lowest_bit.hpp

     3 //

     4 //           Position of the lowest bit 'on'

     5 //

     6 //       (C) Copyright Gennaro Prota 2003 - 2004.

     7 //

     8 // Distributed under the Boost Software License, Version 1.0.

     9 //    (See accompanying file LICENSE_1_0.txt or copy at

    10 //          http://www.boost.org/LICENSE_1_0.txt)

    11 //

    12 // ------------------------------------------------------

    13 

    14 #ifndef BOOST_LOWEST_BIT_HPP_GP_20030301

    15 #define BOOST_LOWEST_BIT_HPP_GP_20030301

    16 

    17 #include <cassert>

    18 #include "boost/pending/integer_log2.hpp"

    19 

    20 

    21 namespace boost {

    22 

    23     template <typename T>

    24     int lowest_bit(T x) {

    25 

    26         assert(x >= 1); // PRE

    27 

    28         // clear all bits on except the rightmost one,

    29         // then calculate the logarithm base 2

    30         //

    31         return boost::integer_log2<T>( x - ( x & (x-1) ) );

    32 

    33     }

    34 

    35 

    36 }

    37 

    38 

    39 #endif // include guard