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1 | /*! |
2 | @file | |
3 | Forward declares `boost::hana::negate`. | |
4 | ||
5 | @copyright Louis Dionne 2013-2016 | |
6 | Distributed under the Boost Software License, Version 1.0. | |
7 | (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) | |
8 | */ | |
9 | ||
10 | #ifndef BOOST_HANA_FWD_NEGATE_HPP | |
11 | #define BOOST_HANA_FWD_NEGATE_HPP | |
12 | ||
13 | #include <boost/hana/config.hpp> | |
14 | #include <boost/hana/core/when.hpp> | |
15 | ||
16 | ||
17 | BOOST_HANA_NAMESPACE_BEGIN | |
18 | //! Return the inverse of an element of a group. | |
19 | //! @ingroup group-Group | |
20 | //! | |
21 | //! | |
22 | //! Example | |
23 | //! ------- | |
24 | //! @include example/negate.cpp | |
25 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
26 | constexpr auto negate = [](auto&& x) -> decltype(auto) { | |
27 | return tag-dispatched; | |
28 | }; | |
29 | #else | |
30 | template <typename G, typename = void> | |
31 | struct negate_impl : negate_impl<G, when<true>> { }; | |
32 | ||
33 | struct negate_t { | |
34 | template <typename X> | |
35 | constexpr decltype(auto) operator()(X&& x) const; | |
36 | }; | |
37 | ||
38 | constexpr negate_t negate{}; | |
39 | #endif | |
40 | BOOST_HANA_NAMESPACE_END | |
41 | ||
42 | #endif // !BOOST_HANA_FWD_NEGATE_HPP |