// Copyright (c) 2016-2020 Antony Polukhin
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_PFR_CORE_HPP
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#define BOOST_PFR_CORE_HPP
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#pragma once
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#include <boost/pfr/detail/config.hpp>
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#include <boost/pfr/detail/core.hpp>
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#include <boost/pfr/detail/sequence_tuple.hpp>
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#include <boost/pfr/detail/stdtuple.hpp>
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#include <boost/pfr/detail/for_each_field_impl.hpp>
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#include <boost/pfr/detail/make_integer_sequence.hpp>
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#include <boost/pfr/detail/tie_from_structure_tuple.hpp>
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#include <type_traits>
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#include <utility> // metaprogramming stuff
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#include <boost/pfr/tuple_size.hpp>
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/// \file boost/pfr/core.hpp
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/// Contains all the basic tuple-like interfaces \forcedlink{get}, \forcedlink{tuple_size}, \forcedlink{tuple_element_t}, and others.
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///
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/// \b Synopsis:
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namespace boost { namespace pfr {
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/// \brief Returns reference or const reference to a field with index `I` in \aggregate `val`.
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///
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/// \b Example:
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/// \code
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/// struct my_struct { int i, short s; };
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/// my_struct s {10, 11};
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/// assert(boost::pfr::get<0>(s) == 10);
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/// boost::pfr::get<1>(s) = 0;
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/// \endcode
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template <std::size_t I, class T>
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constexpr decltype(auto) get(const T& val) noexcept {
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return detail::sequence_tuple::get<I>( detail::tie_as_tuple(val) );
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}
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/// \overload get
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template <std::size_t I, class T>
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constexpr decltype(auto) get(T& val
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#if !BOOST_PFR_USE_CPP17
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, std::enable_if_t<std::is_assignable<T, T>::value>* = nullptr
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#endif
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) noexcept {
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return detail::sequence_tuple::get<I>( detail::tie_as_tuple(val) );
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}
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#if !BOOST_PFR_USE_CPP17
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/// \overload get
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template <std::size_t I, class T>
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constexpr auto get(T&, std::enable_if_t<!std::is_assignable<T, T>::value>* = nullptr) noexcept {
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static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::get on non const non assignable type is allowed only in C++17");
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return 0;
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}
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#endif
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/// \overload get
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template <std::size_t I, class T>
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constexpr auto get(T&& val, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = 0) noexcept {
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return std::move(detail::sequence_tuple::get<I>( detail::tie_as_tuple(val) ));
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}
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/// \brief `tuple_element` has a member typedef `type` that returns the type of a field with index I in \aggregate T.
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///
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/// \b Example:
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/// \code
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/// std::vector< boost::pfr::tuple_element<0, my_structure>::type > v;
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/// \endcode
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template <std::size_t I, class T>
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using tuple_element = detail::sequence_tuple::tuple_element<I, decltype( ::boost::pfr::detail::tie_as_tuple(std::declval<T&>()) ) >;
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/// \brief Type of a field with index `I` in \aggregate `T`.
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///
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/// \b Example:
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/// \code
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/// std::vector< boost::pfr::tuple_element_t<0, my_structure> > v;
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/// \endcode
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template <std::size_t I, class T>
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using tuple_element_t = typename tuple_element<I, T>::type;
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/// \brief Creates a `std::tuple` from fields of an \aggregate `val`.
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///
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/// \b Example:
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/// \code
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/// struct my_struct { int i, short s; };
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/// my_struct s {10, 11};
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/// std::tuple<int, short> t = make_tuple(s);
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/// assert(get<0>(t) == 10);
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/// \endcode
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template <class T>
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constexpr auto structure_to_tuple(const T& val) noexcept {
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return detail::make_stdtuple_from_tietuple(
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detail::tie_as_tuple(val),
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detail::make_index_sequence< tuple_size_v<T> >()
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);
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}
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/// \brief std::tie` like function that ties fields of a structure.
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///
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/// \returns a `std::tuple` with lvalue and const lvalue references to fields of an \aggregate `val`.
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///
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/// \b Example:
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/// \code
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/// void foo(const int&, const short&);
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/// struct my_struct { int i, short s; };
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///
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/// const my_struct const_s{1, 2};
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/// std::apply(foo, structure_tie(const_s));
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///
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/// my_struct s;
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/// structure_tie(s) = std::tuple<int, short>{10, 11};
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/// assert(s.s == 11);
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/// \endcode
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template <class T>
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constexpr auto structure_tie(const T& val) noexcept {
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return detail::make_conststdtiedtuple_from_tietuple(
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detail::tie_as_tuple(const_cast<T&>(val)),
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detail::make_index_sequence< tuple_size_v<T> >()
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);
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}
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/// \overload structure_tie
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template <class T>
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constexpr auto structure_tie(T& val
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#if !BOOST_PFR_USE_CPP17
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, std::enable_if_t<std::is_assignable<T, T>::value>* = nullptr
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#endif
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) noexcept {
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return detail::make_stdtiedtuple_from_tietuple(
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detail::tie_as_tuple(val),
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detail::make_index_sequence< tuple_size_v<T> >()
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);
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}
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#if !BOOST_PFR_USE_CPP17
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/// \overload structure_tie
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template <class T>
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constexpr auto structure_tie(T&, std::enable_if_t<!std::is_assignable<T, T>::value>* = nullptr) noexcept {
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static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::structure_tie on non const non assignable type is allowed only in C++17");
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return 0;
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}
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#endif
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/// \overload structure_tie
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template <class T>
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constexpr auto structure_tie(T&&, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = 0) noexcept {
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static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::structure_tie on rvalue references is forbidden");
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return 0;
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}
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/// Calls `func` for each field of a `value`.
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///
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/// \param func must have one of the following signatures:
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/// * any_return_type func(U&& field) // field of value is perfect forwarded to function
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/// * any_return_type func(U&& field, std::size_t i)
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/// * any_return_type func(U&& value, I i) // Here I is an `std::integral_constant<size_t, field_index>`
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///
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/// \param value To each field of this variable will be the `func` applied.
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///
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/// \b Example:
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/// \code
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/// struct my_struct { int i, short s; };
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/// int sum = 0;
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/// for_each_field(my_struct{20, 22}, [&sum](const auto& field) { sum += field; });
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/// assert(sum == 42);
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/// \endcode
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template <class T, class F>
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void for_each_field(T&& value, F&& func) {
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constexpr std::size_t fields_count_val = boost::pfr::detail::fields_count<std::remove_reference_t<T>>();
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::boost::pfr::detail::for_each_field_dispatcher(
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value,
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[f = std::forward<F>(func)](auto&& t) mutable {
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// MSVC related workaround. Its lambdas do not capture constexprs.
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constexpr std::size_t fields_count_val_in_lambda
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= boost::pfr::detail::fields_count<std::remove_reference_t<T>>();
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::boost::pfr::detail::for_each_field_impl(
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t,
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std::forward<F>(f),
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detail::make_index_sequence<fields_count_val_in_lambda>{},
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std::is_rvalue_reference<T&&>{}
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);
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},
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detail::make_index_sequence<fields_count_val>{}
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);
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}
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/// \brief std::tie-like function that allows assigning to tied values from aggregates.
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///
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/// \returns an object with lvalue references to `args...`; on assignment of an \aggregate value to that
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/// object each field of an aggregate is assigned to the corresponding `args...` reference.
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///
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/// \b Example:
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/// \code
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/// auto f() {
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/// struct { struct { int x, y } p; short s; } res { { 4, 5 }, 6 };
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/// return res;
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/// }
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/// auto [p, s] = f();
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/// tie_from_structure(p, s) = f();
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/// \endcode
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template <typename... Elements>
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constexpr detail::tie_from_structure_tuple<Elements...> tie_from_structure(Elements&... args) noexcept {
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return detail::tie_from_structure_tuple<Elements...>(args...);
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}
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}} // namespace boost::pfr
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#endif // BOOST_PFR_CORE_HPP
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