1 | /////////////////////////////////////////////////////////////////////////////// |
2 | // moment.hpp |
3 | // |
4 | // Copyright 2005 Eric Niebler. Distributed under the Boost |
5 | // Software License, Version 1.0. (See accompanying file |
6 | // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
7 | |
8 | #ifndef BOOST_ACCUMULATORS_STATISTICS_MOMENT_HPP_EAN_15_11_2005 |
9 | #define BOOST_ACCUMULATORS_STATISTICS_MOMENT_HPP_EAN_15_11_2005 |
10 | |
11 | #include <boost/config/no_tr1/cmath.hpp> |
12 | #include <boost/mpl/int.hpp> |
13 | #include <boost/mpl/assert.hpp> |
14 | #include <boost/mpl/placeholders.hpp> |
15 | #include <boost/accumulators/framework/accumulator_base.hpp> |
16 | #include <boost/accumulators/framework/extractor.hpp> |
17 | #include <boost/accumulators/numeric/functional.hpp> |
18 | #include <boost/accumulators/framework/parameters/sample.hpp> |
19 | #include <boost/accumulators/framework/depends_on.hpp> |
20 | #include <boost/accumulators/statistics_fwd.hpp> |
21 | #include <boost/accumulators/statistics/count.hpp> |
22 | |
23 | namespace boost { namespace numeric |
24 | { |
25 | /// INTERNAL ONLY |
26 | /// |
27 | template<typename T> |
28 | T const &pow(T const &x, mpl::int_<1>) |
29 | { |
30 | return x; |
31 | } |
32 | |
33 | /// INTERNAL ONLY |
34 | /// |
35 | template<typename T, int N> |
36 | T pow(T const &x, mpl::int_<N>) |
37 | { |
38 | using namespace operators; |
39 | T y = numeric::pow(x, mpl::int_<N/2>()); |
40 | T z = y * y; |
41 | return (N % 2) ? (z * x) : z; |
42 | } |
43 | }} |
44 | |
45 | namespace boost { namespace accumulators |
46 | { |
47 | |
48 | namespace impl |
49 | { |
50 | /////////////////////////////////////////////////////////////////////////////// |
51 | // moment_impl |
52 | template<typename N, typename Sample> |
53 | struct moment_impl |
54 | : accumulator_base // TODO: also depends_on sum of powers |
55 | { |
56 | BOOST_MPL_ASSERT_RELATION(N::value, >, 0); |
57 | // for boost::result_of |
58 | typedef typename numeric::functional::fdiv<Sample, std::size_t>::result_type result_type; |
59 | |
60 | template<typename Args> |
61 | moment_impl(Args const &args) |
62 | : sum(args[sample | Sample()]) |
63 | { |
64 | } |
65 | |
66 | template<typename Args> |
67 | void operator ()(Args const &args) |
68 | { |
69 | this->sum += numeric::pow(args[sample], N()); |
70 | } |
71 | |
72 | template<typename Args> |
73 | result_type result(Args const &args) const |
74 | { |
75 | return numeric::fdiv(this->sum, count(args)); |
76 | } |
77 | |
78 | // make this accumulator serializeable |
79 | template<class Archive> |
80 | void serialize(Archive & ar, const unsigned int file_version) |
81 | { |
82 | ar & sum; |
83 | } |
84 | |
85 | private: |
86 | Sample sum; |
87 | }; |
88 | |
89 | } // namespace impl |
90 | |
91 | /////////////////////////////////////////////////////////////////////////////// |
92 | // tag::moment |
93 | // |
94 | namespace tag |
95 | { |
96 | template<int N> |
97 | struct moment |
98 | : depends_on<count> |
99 | { |
100 | /// INTERNAL ONLY |
101 | /// |
102 | typedef accumulators::impl::moment_impl<mpl::int_<N>, mpl::_1> impl; |
103 | }; |
104 | } |
105 | |
106 | /////////////////////////////////////////////////////////////////////////////// |
107 | // extract::moment |
108 | // |
109 | namespace extract |
110 | { |
111 | BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, , (int)) |
112 | } |
113 | |
114 | using extract::moment; |
115 | |
116 | // So that moment<N> can be automatically substituted with |
117 | // weighted_moment<N> when the weight parameter is non-void |
118 | template<int N> |
119 | struct as_weighted_feature<tag::moment<N> > |
120 | { |
121 | typedef tag::weighted_moment<N> type; |
122 | }; |
123 | |
124 | template<int N> |
125 | struct feature_of<tag::weighted_moment<N> > |
126 | : feature_of<tag::moment<N> > |
127 | { |
128 | }; |
129 | |
130 | }} // namespace boost::accumulators |
131 | |
132 | #endif |
133 | |