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+/*!
+@file
+Forward declares `boost::hana::intersection`.
+
+@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_FWD_INTERSECTION_HPP
+#define BOOST_HANA_FWD_INTERSECTION_HPP
+
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/when.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+ //! Returns the intersection of two sets.
+ //! @relates hana::set
+ //!
+ //! Given two sets `xs` and `ys`, `intersection(xs, ys)` is a new set
+ //! containing exactly those elements that are present both in `xs` and
+ //! in `ys`. In other words, the following holds for any object `x`:
+ //! @code
+ //! x ^in^ intersection(xs, ys) if and only if x ^in^ xs && x ^in^ ys
+ //! @endcode
+ //!
+ //!
+ //! @param xs, ys
+ //! Two sets to intersect.
+ //!
+ //!
+ //! Example
+ //! -------
+ //! @include example/intersection.cpp
+ //!
+ //!
+ //! Benchmarks
+ //! ----------
+ //! <div class="benchmark-chart"
+ //! style="min-width: 310px; height: 400px; margin: 0 auto"
+ //! data-dataset="benchmark.intersection.compile.json">
+ //! </div>
+#ifdef BOOST_HANA_DOXYGEN_INVOKED
+ constexpr auto intersection = [](auto&& xs, auto&& ys) {
+ return tag-dispatched;
+ };
+#else
+ template <typename S, typename = void>
+ struct intersection_impl : intersection_impl<S, when<true>> { };
+
+ struct intersection_t {
+ template <typename Xs, typename Ys>
+ constexpr auto operator()(Xs&& xs, Ys&& ys) const;
+ };
+
+ constexpr intersection_t intersection{};
+#endif
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_FWD_INTERSECTION_HPP