projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | /*! |
| 2 | @file | |
| 3 | Defines `boost::hana::flip`. | |
| 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_FUNCTIONAL_FLIP_HPP | |
| 11 | #define BOOST_HANA_FUNCTIONAL_FLIP_HPP | |
| 12 | ||
| 13 | #include <boost/hana/config.hpp> | |
| 14 | #include <boost/hana/detail/create.hpp> | |
| 15 | ||
| 16 | #include <utility> | |
| 17 | ||
| 18 | ||
| 19 | BOOST_HANA_NAMESPACE_BEGIN | |
| 20 | //! @ingroup group-functional | |
| 21 | //! Invoke a function with its two first arguments reversed. | |
| 22 | //! | |
| 23 | //! Specifically, `flip(f)` is a function such that | |
| 24 | //! @code | |
| 25 | //! flip(f)(x, y, z...) == f(y, x, z...) | |
| 26 | //! @endcode | |
| 27 | //! | |
| 28 | //! ### Example | |
| 29 | //! @include example/functional/flip.cpp | |
| 30 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
| 31 | constexpr auto flip = [](auto&& f) { | |
| 32 | return [perfect-capture](auto&& x, auto&& y, auto&& ...z) -> decltype(auto) { | |
| 33 | return forwarded(f)(forwarded(y), forwarded(x), forwarded(z)...); | |
| 34 | }; | |
| 35 | }; | |
| 36 | #else | |
| 37 | template <typename F> | |
| 38 | struct flip_t { | |
| 39 | F f; | |
| 40 | ||
| 41 | template <typename X, typename Y, typename ...Z> | |
| 42 | constexpr decltype(auto) operator()(X&& x, Y&& y, Z&& ...z) const& { | |
| 43 | return f( | |
| 44 | static_cast<Y&&>(y), | |
| 45 | static_cast<X&&>(x), | |
| 46 | static_cast<Z&&>(z)... | |
| 47 | ); | |
| 48 | } | |
| 49 | ||
| 50 | template <typename X, typename Y, typename ...Z> | |
| 51 | constexpr decltype(auto) operator()(X&& x, Y&& y, Z&& ...z) & { | |
| 52 | return f( | |
| 53 | static_cast<Y&&>(y), | |
| 54 | static_cast<X&&>(x), | |
| 55 | static_cast<Z&&>(z)... | |
| 56 | ); | |
| 57 | } | |
| 58 | ||
| 59 | template <typename X, typename Y, typename ...Z> | |
| 60 | constexpr decltype(auto) operator()(X&& x, Y&& y, Z&& ...z) && { | |
| 61 | return std::move(f)( | |
| 62 | static_cast<Y&&>(y), | |
| 63 | static_cast<X&&>(x), | |
| 64 | static_cast<Z&&>(z)... | |
| 65 | ); | |
| 66 | } | |
| 67 | }; | |
| 68 | ||
| 69 | constexpr detail::create<flip_t> flip{}; | |
| 70 | #endif | |
| 71 | BOOST_HANA_NAMESPACE_END | |
| 72 | ||
| 73 | #endif // !BOOST_HANA_FUNCTIONAL_FLIP_HPP |