1 // (C) Copyright 2007-2009 Andrew Sutton 2 // 3 // Use, modification and distribution are subject to the 4 // Boost Software License, Version 1.0 (See accompanying file 5 // LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt) 6 7 #ifndef BOOST_GRAPH_NUMERIC_VALUES_HPP 8 #define BOOST_GRAPH_NUMERIC_VALUES_HPP 9 10 #include <limits> 11 12 namespace boost 13 { 14 15 #define BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(type) \ 16 template <> struct numeric_values<type> { \ 17 typedef type value_type; \ 18 static type zero() { return 0.0; } \ 19 static type infinity() { return std::numeric_limits<type>::infinity(); } \ 20 }; 21 22 /** 23 * This generic type reports various numeric values for some type. In the 24 * general case, numeric values simply treat their maximum value as infinity 25 * and the default-constructed value as 0. 26 * 27 * Specializations of this template can redefine the notions of zero and 28 * infinity for various types. For example, the class is specialized for 29 * floating point types to use the built in notion of infinity. 30 */ 31 template <typename T> 32 struct numeric_values 33 { 34 typedef T value_type; 35 zeroboost::numeric_values36 static T zero() 37 { return T(); } 38 infinityboost::numeric_values39 static T infinity() 40 { return (std::numeric_limits<T>::max)(); } 41 }; 42 43 // Specializations for floating point types refer to 0.0 and their infinity 44 // value defined by numeric_limits. 45 BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(float) 46 BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(double) 47 BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(long double) 48 49 #undef BOOST_GRAPH_SPECIALIZE_NUMERIC_VALUE 50 } 51 52 #endif 53