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 | |
39 | static T zero() { return T(); } |
40 | |
41 | 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 | |