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