If I turn on gcc's -Wextra option when compiling code that uses an accumulator with tag::max, I get a screen full of compiler warnings: [wheeler@cib: /var/tmp/acc] cat acc.cpp #include <iostream> #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics/stats.hpp> #include <boost/accumulators/statistics/max.hpp> using namespace boost::accumulators; int main() { accumulator_set<double, stats<tag::max> > acc; acc(1.2); acc(2.3); acc(3.4); acc(4.5); std::cout << "Max: " << max(acc) << std::endl; return 0; } [wheeler@cib: /var/tmp/acc] g++ -W -I /opt/ros/include/boost-1_37/ acc.cpp -o acc /opt/ros/include/boost-1_37/boost/concept_check.hpp: In instantiation of ‘boost::UnaryFunction<boost::numeric::functional::as_min<const double, void>, double, const double&>’: /opt/ros/include/boost-1_37/boost/concept/detail/has_constraints.hpp:40: instantiated from ‘const bool boost::concept::not_satisfied<boost::UnaryFunction<boost::numeric::functional::as_min<const double, void>, double, const double&> >::value’ /opt/ros/include/boost-1_37/boost/concept/detail/has_constraints.hpp:43: instantiated from ‘boost::concept::not_satisfied<boost::UnaryFunction<boost::numeric::functional::as_min<const double, void>, double, const double&> >’ /opt/ros/include/boost-1_37/boost/mpl/if.hpp:67: instantiated from ‘boost::mpl::if_<boost::concept::not_satisfied<boost::UnaryFunction<boost::numeric::functional::as_min<const double, void>, double, const double&> >, boost::concept::constraint<boost::UnaryFunction<boost::numeric::functional::as_min<const double, void>, double, const double&> >, boost::concept::requirement<boost::UnaryFunction<boost::numeric::functional::as_min<const double, void>, double, const double&> > >’ /opt/ros/include/boost-1_37/boost/concept/detail/general.hpp:19: instantiated from ‘boost::concept::requirement_<void (*)(boost::UnaryFunction<boost::numeric::functional::as_min<const double, void>, double, const double&>)>’ /opt/ros/include/boost-1_37/boost/accumulators/numeric/detail/function1.hpp:67: instantiated from ‘typename boost::detail::function1<F>::result<boost::detail::function1<F> ()(const A0&)>::type boost::detail::function1<F>::operator()(const A0&) const [with A0 = double, F = boost::numeric::functional::as_min<mpl_::arg<-0x00000000000000001>, boost::numeric::functional::tag<mpl_::arg<-0x00000000000000001> > >]’ /opt/ros/include/boost-1_37/boost/accumulators/statistics/max.hpp:36: instantiated from ‘boost::accumulators::impl::max_impl<Sample>::max_impl(const Args&) [with Args = boost::parameter::aux::arg_list<boost::parameter::aux::tagged_argument<boost::accumulators::tag::accumulator, boost::accumulators::accumulator_set<double, boost::accumulators::stats<boost::accumulators::tag::max, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, void> >, boost::parameter::aux::empty_arg_list>, Sample = double]’ /opt/ros/include/boost-1_37/boost/accumulators/framework/depends_on.hpp:282: instantiated from ‘boost::accumulators::detail::accumulator_wrapper<Accumulator, Feature>::accumulator_wrapper(const Args&) [with Args = boost::parameter::aux::arg_list<boost::parameter::aux::tagged_argument<boost::accumulators::tag::accumulator, boost::accumulators::accumulator_set<double, boost::accumulators::stats<boost::accumulators::tag::max, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, void> >, boost::parameter::aux::empty_arg_list>, Accumulator = boost::accumulators::impl::max_impl<double>, Feature = boost::accumulators::tag::max]’ /opt/ros/include/boost-1_37/boost/accumulators/framework/depends_on.hpp:215: instantiated from ‘static boost::fusion::cons<typename boost::fusion::result_of::value_of<Iterator>::type, typename boost::accumulators::detail::build_acc_list<typename boost::fusion::result_of::next<Iterator>::type, Last, boost::fusion::result_of::equal_to<typename boost::fusion::result_of::next<Iterator>::type,Last>::value>::type> boost::accumulators::detail::build_acc_list<First, Last, false>::call(const Args&, const First&, const Last&) [with Args = boost::parameter::aux::arg_list<boost::parameter::aux::tagged_argument<boost::accumulators::tag::accumulator, boost::accumulators::accumulator_set<double, boost::accumulators::stats<boost::accumulators::tag::max, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, void> >, boost::parameter::aux::empty_arg_list>, First = boost::fusion::mpl_iterator<boost::mpl::v_iter<boost::mpl::v_item<boost::accumulators::detail::accumulator_wrapper<boost::accumulators::impl::max_impl<double>, boost::accumulators::tag::max>, boost::mpl::vector0<mpl_::na>, 0>, 0l> >, Last = boost::fusion::mpl_iterator<boost::mpl::v_iter<boost::mpl::v_item<boost::accumulators::detail::accumulator_wrapper<boost::accumulators::impl::max_impl<double>, boost::accumulators::tag::max>, boost::mpl::vector0<mpl_::na>, 0>, 1l> >]’ /opt/ros/include/boost-1_37/boost/accumulators/framework/depends_on.hpp:234: instantiated from ‘typename boost::accumulators::detail::meta::make_acc_list<Sequence>::type boost::accumulators::detail::make_acc_list(const Sequence&, const Args&) [with Sequence = boost::mpl::v_item<boost::accumulators::detail::accumulator_wrapper<boost::accumulators::impl::max_impl<double>, boost::accumulators::tag::max>, boost::mpl::vector0<mpl_::na>, 0>, Args = boost::parameter::aux::arg_list<boost::parameter::aux::tagged_argument<boost::accumulators::tag::accumulator, boost::accumulators::accumulator_set<double, boost::accumulators::stats<boost::accumulators::tag::max, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, void> >, boost::parameter::aux::empty_arg_list>]’ /opt/ros/include/boost-1_37/boost/accumulators/framework/accumulator_set.hpp:145: instantiated from ‘boost::accumulators::accumulator_set<Sample, Features, Weight>::accumulator_set() [with Sample = double, Features = boost::accumulators::stats<boost::accumulators::tag::max, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, Weight = void]’ acc.cpp:9: instantiated from here /opt/ros/include/boost-1_37/boost/concept_check.hpp:325: warning: non-static reference ‘const double& boost::UnaryFunction<boost::numeric::functional::as_min<const double, void>, double, const double&>::arg’ in class without a constructor