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