// 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_ARGUMENT_TRAITS_HPP
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#define BOOST_HISTOGRAM_DETAIL_ARGUMENT_TRAITS_HPP
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#include <boost/histogram/fwd.hpp>
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#include <boost/mp11/algorithm.hpp>
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#include <boost/mp11/integral.hpp>
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#include <boost/mp11/list.hpp>
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#include <tuple>
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namespace boost {
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namespace histogram {
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namespace detail {
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template <class T>
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struct is_weight_impl : mp11::mp_false {};
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template <class T>
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struct is_weight_impl<weight_type<T>> : mp11::mp_true {};
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template <class T>
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using is_weight = is_weight_impl<T>;
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template <class T>
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struct is_sample_impl : mp11::mp_false {};
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template <class T>
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struct is_sample_impl<sample_type<T>> : mp11::mp_true {};
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template <class T>
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using is_sample = is_sample_impl<T>;
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template <int Idx, class L>
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struct sample_args_impl {
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using type = mp11::mp_first<std::decay_t<mp11::mp_at_c<L, (Idx >= 0 ? Idx : 0)>>>;
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};
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template <class L>
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struct sample_args_impl<-1, L> {
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using type = std::tuple<>;
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};
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template <std::size_t NArgs, std::size_t Start, int WeightPos, int SamplePos,
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class SampleArgs>
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struct argument_traits_holder {
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using nargs = mp11::mp_size_t<NArgs>;
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using start = mp11::mp_size_t<Start>;
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using wpos = mp11::mp_int<WeightPos>;
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using spos = mp11::mp_int<SamplePos>;
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using sargs = SampleArgs;
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};
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template <class... Ts>
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struct argument_traits_impl {
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using list_ = mp11::mp_list<Ts...>;
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static constexpr std::size_t size_ = sizeof...(Ts);
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static constexpr std::size_t weight_ = mp11::mp_find_if<list_, is_weight>::value;
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static constexpr std::size_t sample_ = mp11::mp_find_if<list_, is_sample>::value;
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static constexpr int spos_ = (sample_ < size_ ? static_cast<int>(sample_) : -1);
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static constexpr int wpos_ = (weight_ < size_ ? static_cast<int>(weight_) : -1);
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using type =
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argument_traits_holder<(size_ - (weight_ < size_) - (sample_ < size_)),
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(weight_ < size_ && sample_ < size_ &&
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(weight_ + sample_ < 2)
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? 2
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: ((weight_ == 0 || sample_ == 0) ? 1 : 0)),
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wpos_, spos_, typename sample_args_impl<spos_, list_>::type>;
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};
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template <class... Ts>
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using argument_traits = typename argument_traits_impl<Ts...>::type;
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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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