Chris@16: // -----------------------------------------------------------
Chris@16: // lowest_bit.hpp
Chris@16: //
Chris@16: //           Position of the lowest bit 'on'
Chris@16: //
Chris@16: //         Copyright (c) 2003-2004, 2008 Gennaro Prota
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0.
Chris@16: //    (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: //          http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // -----------------------------------------------------------
Chris@16: 
Chris@16: #ifndef BOOST_LOWEST_BIT_HPP_GP_20030301
Chris@16: #define BOOST_LOWEST_BIT_HPP_GP_20030301
Chris@16: 
Chris@16: #include <assert.h>
Chris@16: #include "boost/pending/integer_log2.hpp"
Chris@16: 
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16:     template <typename T>
Chris@16:     int lowest_bit(T x) {
Chris@16: 
Chris@16:         assert(x >= 1); // PRE
Chris@16: 
Chris@16:         // clear all bits on except the rightmost one,
Chris@16:         // then calculate the logarithm base 2
Chris@16:         //
Chris@16:         return boost::integer_log2<T>( x - ( x & (x-1) ) );
Chris@16: 
Chris@16:     }
Chris@16: 
Chris@16: 
Chris@16: }
Chris@16: 
Chris@16: 
Chris@16: #endif // include guard