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