// In header: <boost/accumulators/statistics/rolling_mean.hpp>
template<typename Sample> 
struct lazy_rolling_mean_impl : public accumulator_base {
  // types
  typedef numeric::functional::fdiv< Sample, std::size_t, void, void >::result_type result_type;
  // construct/copy/destruct
  lazy_rolling_mean_impl(dont_care);
  // public member functions
  template<typename Args> result_type result(Args const &) const;
};