Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // moment.hpp
Chris@16: //
Chris@16: //  Copyright 2005 Eric Niebler. Distributed under the Boost
Chris@16: //  Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_ACCUMULATORS_STATISTICS_MOMENT_HPP_EAN_15_11_2005
Chris@16: #define BOOST_ACCUMULATORS_STATISTICS_MOMENT_HPP_EAN_15_11_2005
Chris@16: 
Chris@16: #include <boost/config/no_tr1/cmath.hpp>
Chris@16: #include <boost/mpl/int.hpp>
Chris@16: #include <boost/mpl/assert.hpp>
Chris@16: #include <boost/mpl/placeholders.hpp>
Chris@16: #include <boost/accumulators/framework/accumulator_base.hpp>
Chris@16: #include <boost/accumulators/framework/extractor.hpp>
Chris@16: #include <boost/accumulators/numeric/functional.hpp>
Chris@16: #include <boost/accumulators/framework/parameters/sample.hpp>
Chris@16: #include <boost/accumulators/framework/depends_on.hpp>
Chris@16: #include <boost/accumulators/statistics_fwd.hpp>
Chris@16: #include <boost/accumulators/statistics/count.hpp>
Chris@16: 
Chris@16: namespace boost { namespace numeric
Chris@16: {
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<typename T>
Chris@16:     T const &pow(T const &x, mpl::int_<1>)
Chris@16:     {
Chris@16:         return x;
Chris@16:     }
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<typename T, int N>
Chris@16:     T pow(T const &x, mpl::int_<N>)
Chris@16:     {
Chris@16:         using namespace operators;
Chris@16:         T y = numeric::pow(x, mpl::int_<N/2>());
Chris@16:         T z = y * y;
Chris@16:         return (N % 2) ? (z * x) : z;
Chris@16:     }
Chris@16: }}
Chris@16: 
Chris@16: namespace boost { namespace accumulators
Chris@16: {
Chris@16: 
Chris@16: namespace impl
Chris@16: {
Chris@16:     ///////////////////////////////////////////////////////////////////////////////
Chris@16:     // moment_impl
Chris@16:     template<typename N, typename Sample>
Chris@16:     struct moment_impl
Chris@16:       : accumulator_base // TODO: also depends_on sum of powers
Chris@16:     {
Chris@16:         BOOST_MPL_ASSERT_RELATION(N::value, >, 0);
Chris@16:         // for boost::result_of
Chris@16:         typedef typename numeric::functional::fdiv<Sample, std::size_t>::result_type result_type;
Chris@16: 
Chris@16:         template<typename Args>
Chris@16:         moment_impl(Args const &args)
Chris@16:           : sum(args[sample | Sample()])
Chris@16:         {
Chris@16:         }
Chris@16: 
Chris@16:         template<typename Args>
Chris@16:         void operator ()(Args const &args)
Chris@16:         {
Chris@16:             this->sum += numeric::pow(args[sample], N());
Chris@16:         }
Chris@16: 
Chris@16:         template<typename Args>
Chris@16:         result_type result(Args const &args) const
Chris@16:         {
Chris@16:             return numeric::fdiv(this->sum, count(args));
Chris@16:         }
Chris@16: 
Chris@16:     private:
Chris@16:         Sample sum;
Chris@16:     };
Chris@16: 
Chris@16: } // namespace impl
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // tag::moment
Chris@16: //
Chris@16: namespace tag
Chris@16: {
Chris@16:     template<int N>
Chris@16:     struct moment
Chris@16:       : depends_on<count>
Chris@16:     {
Chris@16:         /// INTERNAL ONLY
Chris@16:         ///
Chris@16:         typedef accumulators::impl::moment_impl<mpl::int_<N>, mpl::_1> impl;
Chris@16:     };
Chris@16: }
Chris@16: 
Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: // extract::moment
Chris@16: //
Chris@16: namespace extract
Chris@16: {
Chris@16:     BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, moment, (int))
Chris@16: }
Chris@16: 
Chris@16: using extract::moment;
Chris@16: 
Chris@16: // So that moment<N> can be automatically substituted with
Chris@16: // weighted_moment<N> when the weight parameter is non-void
Chris@16: template<int N>
Chris@16: struct as_weighted_feature<tag::moment<N> >
Chris@16: {
Chris@16:     typedef tag::weighted_moment<N> type;
Chris@16: };
Chris@16: 
Chris@16: template<int N>
Chris@16: struct feature_of<tag::weighted_moment<N> >
Chris@16:   : feature_of<tag::moment<N> >
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: }} // namespace boost::accumulators
Chris@16: 
Chris@16: #endif