Last change
on this file since 47 was
29,
checked in by landauf, 16 years ago
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updated boost from 1_33_1 to 1_34_1
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File size:
853 bytes
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1 | // ------------------------------------- |
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2 | // lowest_bit.hpp |
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3 | // |
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4 | // Position of the lowest bit 'on' |
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5 | // |
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6 | // (C) Copyright Gennaro Prota 2003 - 2004. |
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7 | // |
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8 | // Distributed under the Boost Software License, Version 1.0. |
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9 | // (See accompanying file LICENSE_1_0.txt or copy at |
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10 | // http://www.boost.org/LICENSE_1_0.txt) |
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11 | // |
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12 | // ------------------------------------------------------ |
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13 | |
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14 | #ifndef BOOST_LOWEST_BIT_HPP_GP_20030301 |
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15 | #define BOOST_LOWEST_BIT_HPP_GP_20030301 |
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16 | |
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17 | #include <cassert> |
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18 | #include "boost/pending/integer_log2.hpp" |
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19 | |
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20 | |
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21 | namespace boost { |
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22 | |
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23 | template <typename T> |
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24 | int lowest_bit(T x) { |
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25 | |
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26 | assert(x >= 1); // PRE |
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27 | |
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28 | // clear all bits on except the rightmost one, |
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29 | // then calculate the logarithm base 2 |
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30 | // |
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31 | return boost::integer_log2<T>( x - ( x & (x-1) ) ); |
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32 | |
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33 | } |
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34 | |
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35 | |
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36 | } |
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37 | |
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38 | |
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39 | #endif // include guard |
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