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1 // (C) Copyright 2007-2009 Andrew Sutton
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2 //
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3 // Use, modification and distribution are subject to the
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4 // Boost Software License, Version 1.0 (See accompanying file
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5 // LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
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6
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7 #ifndef BOOST_GRAPH_NUMERIC_VALUES_HPP
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8 #define BOOST_GRAPH_NUMERIC_VALUES_HPP
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9
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10 #include <limits>
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11
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12 namespace boost
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13 {
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14
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15 #define BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(type) \
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16 template <> struct numeric_values<type> { \
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17 typedef type value_type; \
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18 static type zero() { return 0.0; } \
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19 static type infinity() { return std::numeric_limits<type>::infinity(); } \
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20 };
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21
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22 /**
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23 * This generic type reports various numeric values for some type. In the
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24 * general case, numeric values simply treat their maximum value as infinity
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25 * and the default-constructed value as 0.
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26 *
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27 * Specializations of this template can redefine the notions of zero and
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28 * infinity for various types. For example, the class is specialized for
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29 * floating point types to use the built in notion of infinity.
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30 */
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31 template <typename T>
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32 struct numeric_values
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33 {
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34 typedef T value_type;
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35
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36 static T zero()
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37 { return T(); }
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38
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39 static T infinity()
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40 { return (std::numeric_limits<T>::max)(); }
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41 };
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42
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43 // Specializations for floating point types refer to 0.0 and their infinity
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44 // value defined by numeric_limits.
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45 BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(float)
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46 BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(double)
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47 BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(long double)
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48
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49 #undef BOOST_GRAPH_SPECIALIZE_NUMERIC_VALUE
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50 }
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51
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52 #endif
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