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+/*!
+@file
+Defines `boost::hana::insert`.
+
+@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_INSERT_HPP
+#define BOOST_HANA_INSERT_HPP
+
+#include <boost/hana/fwd/insert.hpp>
+
+#include <boost/hana/append.hpp>
+#include <boost/hana/concat.hpp>
+#include <boost/hana/concept/sequence.hpp>
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/dispatch.hpp>
+#include <boost/hana/drop_front.hpp>
+#include <boost/hana/take_front.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+ //! @cond
+ template <typename Set, typename ...Args>
+ constexpr decltype(auto) insert_t::operator()(Set&& set, Args&& ...args) const {
+ return insert_impl<typename hana::tag_of<Set>::type>::apply(
+ static_cast<Set&&>(set),
+ static_cast<Args&&>(args)...
+ );
+ }
+ //! @endcond
+
+ template <typename T, bool condition>
+ struct insert_impl<T, when<condition>> : default_ {
+ template <typename ...Args>
+ static constexpr auto apply(Args&& ...) = delete;
+ };
+
+ template <typename S>
+ struct insert_impl<S, when<Sequence<S>::value>> {
+ template <typename Xs, typename N, typename Element>
+ static constexpr auto apply(Xs&& xs, N const& n, Element&& e) {
+ return hana::concat(hana::append(hana::take_front(xs, n),
+ static_cast<Element&&>(e)),
+ hana::drop_front(xs, n));
+ }
+ };
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_INSERT_HPP