// In header: <boost/accumulators/framework/accumulators/value_accumulator.hpp>

template<typename ValueType, typename Tag> 
struct value_accumulator_impl : public boost::accumulators::accumulator_base {
  // types
  typedef ValueType result_type;

  // construct/copy/destruct
  template<typename Args> value_accumulator_impl(Args const &);

  // public member functions
  result_type result(dont_care) const;
};