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- /*!
- @file
- Forward declares `boost::hana::negate`.
- @copyright Louis Dionne 2013-2017
- 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_NEGATE_HPP
- #define BOOST_HANA_FWD_NEGATE_HPP
- #include <boost/hana/config.hpp>
- #include <boost/hana/core/when.hpp>
- BOOST_HANA_NAMESPACE_BEGIN
- //! Return the inverse of an element of a group.
- //! @ingroup group-Group
- //!
- //!
- //! Example
- //! -------
- //! @include example/negate.cpp
- #ifdef BOOST_HANA_DOXYGEN_INVOKED
- constexpr auto negate = [](auto&& x) -> decltype(auto) {
- return tag-dispatched;
- };
- #else
- template <typename G, typename = void>
- struct negate_impl : negate_impl<G, when<true>> { };
- struct negate_t {
- template <typename X>
- constexpr decltype(auto) operator()(X&& x) const;
- };
- constexpr negate_t negate{};
- #endif
- BOOST_HANA_NAMESPACE_END
- #endif // !BOOST_HANA_FWD_NEGATE_HPP
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