// Copyright 2019 Hans Dembinski // // 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_HISTOGRAM_DETAIL_ACCUMULATOR_TRAITS_HPP #define BOOST_HISTOGRAM_DETAIL_ACCUMULATOR_TRAITS_HPP #include <boost/histogram/detail/priority.hpp> #include <boost/histogram/fwd.hpp> #include <tuple> #include <type_traits> namespace boost { // forward declare accumulator_set so that it can be matched below namespace accumulators { template <class, class, class> struct accumulator_set; } namespace histogram { namespace detail { template <bool WeightSupport, class... Ts> struct accumulator_traits_holder { static constexpr bool weight_support = WeightSupport; using args = std::tuple<Ts...>; }; // member function pointer with weight_type as first argument is better match template <class R, class T, class U, class... Ts> accumulator_traits_holder<true, Ts...> accumulator_traits_impl_call_op( R (T::*)(boost::histogram::weight_type<U>, Ts...)); template <class R, class T, class U, class... Ts> accumulator_traits_holder<true, Ts...> accumulator_traits_impl_call_op( R (T::*)(boost::histogram::weight_type<U>&, Ts...)); template <class R, class T, class U, class... Ts> accumulator_traits_holder<true, Ts...> accumulator_traits_impl_call_op( R (T::*)(boost::histogram::weight_type<U>&&, Ts...)); template <class R, class T, class U, class... Ts> accumulator_traits_holder<true, Ts...> accumulator_traits_impl_call_op( R (T::*)(const boost::histogram::weight_type<U>&, Ts...)); // member function pointer only considered if all specializations above fail template <class R, class T, class... Ts> accumulator_traits_holder<false, Ts...> accumulator_traits_impl_call_op(R (T::*)(Ts...)); template <class T> auto accumulator_traits_impl(T&, priority<2>) -> decltype(accumulator_traits_impl_call_op(&T::operator())); template <class T> auto accumulator_traits_impl(T&, priority<2>) -> decltype(std::declval<T&>() += std::declval<boost::histogram::weight_type<int>>(), accumulator_traits_holder<true>{}); // fallback for simple arithmetic types that do not implement adding a weight_type template <class T> auto accumulator_traits_impl(T&, priority<1>) -> decltype(std::declval<T&>() += 0, accumulator_traits_holder<true>{}); template <class T> auto accumulator_traits_impl(T&, priority<0>) -> accumulator_traits_holder<false>; // for boost.accumulators compatibility template <class S, class F, class W> accumulator_traits_holder<false, S> accumulator_traits_impl( boost::accumulators::accumulator_set<S, F, W>&, priority<2>) { static_assert(std::is_same<W, void>::value, "accumulator_set with weights is not directly supported, please use " "a wrapper class that implements the Accumulator concept"); } template <class T> using accumulator_traits = decltype(accumulator_traits_impl(std::declval<T&>(), priority<2>{})); } // namespace detail } // namespace histogram } // namespace boost #endif