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- /*!
- @file
- Forward declares `boost::hana::union_`.
- @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_UNION_HPP
- #define BOOST_HANA_FWD_UNION_HPP
- #include <boost/hana/config.hpp>
- #include <boost/hana/core/when.hpp>
- BOOST_HANA_NAMESPACE_BEGIN
- //! Returns the union of two sets.
- //! @relates hana::set
- //!
- //! Given two sets `xs` and `ys`, `union_(xs, ys)` is a new set containing
- //! all the elements of `xs` and all the elements of `ys`, without
- //! duplicates. For any object `x`, the following holds:
- //! @code
- //! x ^in^ union_(xs, ys) if and only if x ^in^ xs || x ^in^ ys
- //! @endcode
- //!
- //!
- //! @param xs, ys
- //! Two sets to compute the union of.
- //!
- //!
- //! Example
- //! -------
- //! @include example/union.cpp
- //!
- //!
- //! Benchmarks
- //! ----------
- //! <div class="benchmark-chart"
- //! style="min-width: 310px; height: 400px; margin: 0 auto"
- //! data-dataset="benchmark.union.compile.json">
- //! </div>
- #ifdef BOOST_HANA_DOXYGEN_INVOKED
- constexpr auto union_ = [](auto&& xs, auto&& ys) {
- return tag-dispatched;
- };
- #else
- template <typename S, typename = void>
- struct union_impl : union_impl<S, when<true>> { };
- struct union_t {
- template <typename Xs, typename Ys>
- constexpr auto operator()(Xs&& xs, Ys&& ys) const;
- };
- constexpr union_t union_{};
- #endif
- BOOST_HANA_NAMESPACE_END
- #endif // !BOOST_HANA_FWD_UNION_HPP
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