// Copyright 2019 Hans Dembinski
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_HISTOGRAM_DETAIL_ACCUMULATOR_TRAITS_HPP
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#define BOOST_HISTOGRAM_DETAIL_ACCUMULATOR_TRAITS_HPP
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#include <boost/histogram/detail/priority.hpp>
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#include <boost/histogram/fwd.hpp>
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#include <tuple>
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#include <type_traits>
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namespace boost {
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// forward declare accumulator_set so that it can be matched below
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namespace accumulators {
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template <class, class, class>
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struct accumulator_set;
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}
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namespace histogram {
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namespace detail {
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template <bool WeightSupport, class... Ts>
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struct accumulator_traits_holder {
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static constexpr bool weight_support = WeightSupport;
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using args = std::tuple<Ts...>;
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};
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// member function pointer with weight_type as first argument is better match
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template <class R, class T, class U, class... Ts>
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accumulator_traits_holder<true, Ts...> accumulator_traits_impl_call_op(
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R (T::*)(boost::histogram::weight_type<U>, Ts...));
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template <class R, class T, class U, class... Ts>
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accumulator_traits_holder<true, Ts...> accumulator_traits_impl_call_op(
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R (T::*)(boost::histogram::weight_type<U>&, Ts...));
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template <class R, class T, class U, class... Ts>
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accumulator_traits_holder<true, Ts...> accumulator_traits_impl_call_op(
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R (T::*)(boost::histogram::weight_type<U>&&, Ts...));
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template <class R, class T, class U, class... Ts>
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accumulator_traits_holder<true, Ts...> accumulator_traits_impl_call_op(
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R (T::*)(const boost::histogram::weight_type<U>&, Ts...));
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// member function pointer only considered if all specializations above fail
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template <class R, class T, class... Ts>
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accumulator_traits_holder<false, Ts...> accumulator_traits_impl_call_op(R (T::*)(Ts...));
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template <class T>
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auto accumulator_traits_impl(T&, priority<1>)
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-> decltype(accumulator_traits_impl_call_op(&T::operator()));
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template <class T>
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auto accumulator_traits_impl(T&, priority<1>)
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-> decltype(std::declval<T&>() += 0, accumulator_traits_holder<true>{});
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template <class T>
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auto accumulator_traits_impl(T&, priority<0>) -> accumulator_traits_holder<false>;
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// for boost.accumulators compatibility
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template <class S, class F, class W>
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accumulator_traits_holder<false, S> accumulator_traits_impl(
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boost::accumulators::accumulator_set<S, F, W>&, priority<1>) {
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static_assert(std::is_same<W, void>::value,
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"accumulator_set with weights is not directly supported, please use "
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"a wrapper class that implements the Accumulator concept");
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}
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template <class T>
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using accumulator_traits =
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decltype(accumulator_traits_impl(std::declval<T&>(), priority<1>{}));
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} // namespace detail
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} // namespace histogram
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} // namespace boost
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#endif
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