| /////////////////////////////////////////////////////////////////////////////// |
| // moment.hpp |
| // |
| // Copyright 2005 Eric Niebler. Distributed under the Boost |
| // Software License, Version 1.0. (See accompanying file |
| // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
| |
| #ifndef BOOST_ACCUMULATORS_STATISTICS_MOMENT_HPP_EAN_15_11_2005 |
| #define BOOST_ACCUMULATORS_STATISTICS_MOMENT_HPP_EAN_15_11_2005 |
| |
| #include <boost/config/no_tr1/cmath.hpp> |
| #include <boost/mpl/int.hpp> |
| #include <boost/mpl/assert.hpp> |
| #include <boost/mpl/placeholders.hpp> |
| #include <boost/accumulators/framework/accumulator_base.hpp> |
| #include <boost/accumulators/framework/extractor.hpp> |
| #include <boost/accumulators/numeric/functional.hpp> |
| #include <boost/accumulators/framework/parameters/sample.hpp> |
| #include <boost/accumulators/framework/depends_on.hpp> |
| #include <boost/accumulators/statistics_fwd.hpp> |
| #include <boost/accumulators/statistics/count.hpp> |
| |
| namespace boost { namespace numeric |
| { |
| /// INTERNAL ONLY |
| /// |
| template<typename T> |
| T const &pow(T const &x, mpl::int_<1>) |
| { |
| return x; |
| } |
| |
| /// INTERNAL ONLY |
| /// |
| template<typename T, int N> |
| T pow(T const &x, mpl::int_<N>) |
| { |
| using namespace operators; |
| T y = numeric::pow(x, mpl::int_<N/2>()); |
| T z = y * y; |
| return (N % 2) ? (z * x) : z; |
| } |
| }} |
| |
| namespace boost { namespace accumulators |
| { |
| |
| namespace impl |
| { |
| /////////////////////////////////////////////////////////////////////////////// |
| // moment_impl |
| template<typename N, typename Sample> |
| struct moment_impl |
| : accumulator_base // TODO: also depends_on sum of powers |
| { |
| BOOST_MPL_ASSERT_RELATION(N::value, >, 0); |
| // for boost::result_of |
| typedef typename numeric::functional::average<Sample, std::size_t>::result_type result_type; |
| |
| template<typename Args> |
| moment_impl(Args const &args) |
| : sum(args[sample | Sample()]) |
| { |
| } |
| |
| template<typename Args> |
| void operator ()(Args const &args) |
| { |
| this->sum += numeric::pow(args[sample], N()); |
| } |
| |
| template<typename Args> |
| result_type result(Args const &args) const |
| { |
| return numeric::average(this->sum, count(args)); |
| } |
| |
| private: |
| Sample sum; |
| }; |
| |
| } // namespace impl |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // tag::moment |
| // |
| namespace tag |
| { |
| template<int N> |
| struct moment |
| : depends_on<count> |
| { |
| /// INTERNAL ONLY |
| /// |
| typedef accumulators::impl::moment_impl<mpl::int_<N>, mpl::_1> impl; |
| }; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // extract::moment |
| // |
| namespace extract |
| { |
| BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, moment, (int)) |
| } |
| |
| using extract::moment; |
| |
| // So that moment<N> can be automatically substituted with |
| // weighted_moment<N> when the weight parameter is non-void |
| template<int N> |
| struct as_weighted_feature<tag::moment<N> > |
| { |
| typedef tag::weighted_moment<N> type; |
| }; |
| |
| template<int N> |
| struct feature_of<tag::weighted_moment<N> > |
| : feature_of<tag::moment<N> > |
| { |
| }; |
| |
| }} // namespace boost::accumulators |
| |
| #endif |