/////////////////////////////////////////////////////////////////////////////// | |
// 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 |