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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 | ||
36 | static T zero() | |
37 | { return T(); } | |
38 | ||
39 | 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 |