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+/*!
+@file
+Defines `boost::hana::detail::variadic::take`.
+
+@copyright Louis Dionne 2013-2016
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+ */
+
+#ifndef BOOST_HANA_DETAIL_VARIADIC_TAKE_HPP
+#define BOOST_HANA_DETAIL_VARIADIC_TAKE_HPP
+
+#include <boost/hana/config.hpp>
+#include <boost/hana/detail/variadic/split_at.hpp>
+#include <boost/hana/functional/always.hpp>
+#include <boost/hana/functional/reverse_partial.hpp>
+
+#include <cstddef>
+
+
+BOOST_HANA_NAMESPACE_BEGIN namespace detail { namespace variadic {
+ struct take_impl2 {
+ template <typename F, typename ...Xs>
+ constexpr decltype(auto) operator()(F&& f, Xs&& ...xs) const {
+ return static_cast<F&&>(f)(static_cast<Xs&&>(xs)...);
+ }
+ };
+
+ struct take_impl1 {
+ template <typename ...Xs>
+ constexpr auto operator()(Xs&& ...xs) const {
+ return hana::always(
+ reverse_partial(take_impl2{},
+ static_cast<Xs&&>(xs)...)
+ );
+ }
+ };
+
+ template <std::size_t n>
+ struct take_t {
+ template <typename ...Xs>
+ constexpr decltype(auto) operator()(Xs&& ...xs) const {
+ return variadic::split_at<n>(static_cast<Xs&&>(xs)...)(take_impl1{});
+ }
+ };
+
+ template <std::size_t n>
+ constexpr take_t<n> take{};
+}} BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_DETAIL_VARIADIC_TAKE_HPP