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 { \ 18 typedef type value_type; \ 19 static type zero() { return 0.0; } \ 20 static type infinity() \ 21 { \ 22 return std::numeric_limits< type >::infinity(); \ 23 } \ 24 }; 25 26 /** 27 * This generic type reports various numeric values for some type. In the 28 * general case, numeric values simply treat their maximum value as infinity 29 * and the default-constructed value as 0. 30 * 31 * Specializations of this template can redefine the notions of zero and 32 * infinity for various types. For example, the class is specialized for 33 * floating point types to use the built in notion of infinity. 34 */ 35 template < typename T > struct numeric_values 36 { 37 typedef T value_type; 38 zeroboost::numeric_values39 static T zero() { return T(); } 40 infinityboost::numeric_values41 static T infinity() { return (std::numeric_limits< T >::max)(); } 42 }; 43 44 // Specializations for floating point types refer to 0.0 and their infinity 45 // value defined by numeric_limits. 46 BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(float) 47 BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(double) 48 BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(long double) 49 50 #undef BOOST_GRAPH_SPECIALIZE_NUMERIC_VALUE 51 } 52 53 #endif 54