projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | /*! |
| 2 | @file | |
| 3 | Defines `boost::hana::detail::has_[nontrivial_]common_embedding`. | |
| 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_DETAIL_HAS_COMMON_EMBEDDING_HPP | |
| 11 | #define BOOST_HANA_DETAIL_HAS_COMMON_EMBEDDING_HPP | |
| 12 | ||
| 13 | #include <boost/hana/config.hpp> | |
| 14 | #include <boost/hana/core/common.hpp> | |
| 15 | #include <boost/hana/core/to.hpp> | |
| 16 | #include <boost/hana/detail/void_t.hpp> | |
| 17 | ||
| 18 | #include <type_traits> | |
| 19 | ||
| 20 | ||
| 21 | BOOST_HANA_NAMESPACE_BEGIN namespace detail { | |
| 22 | template <template <typename...> class Concept, typename T, typename U, typename = void> | |
| 23 | struct has_common_embedding_impl : std::false_type { }; | |
| 24 | ||
| 25 | template <template <typename...> class Concept, typename T, typename U> | |
| 26 | struct has_common_embedding_impl<Concept, T, U, detail::void_t< | |
| 27 | typename common<T, U>::type | |
| 28 | >> { | |
| 29 | using Common = typename common<T, U>::type; | |
| 30 | using type = std::integral_constant<bool, | |
| 31 | Concept<T>::value && | |
| 32 | Concept<U>::value && | |
| 33 | Concept<Common>::value && | |
| 34 | is_embedded<T, Common>::value && | |
| 35 | is_embedded<U, Common>::value | |
| 36 | >; | |
| 37 | }; | |
| 38 | ||
| 39 | //! @ingroup group-details | |
| 40 | //! Returns whether `T` and `U` both have an embedding into a | |
| 41 | //! common type. | |
| 42 | //! | |
| 43 | //! If `T` and `U` do not have a common-type, this metafunction returns | |
| 44 | //! false. | |
| 45 | template <template <typename...> class Concept, typename T, typename U> | |
| 46 | using has_common_embedding = typename has_common_embedding_impl<Concept, T, U>::type; | |
| 47 | ||
| 48 | template <template <typename...> class Concept, typename T, typename U> | |
| 49 | struct has_nontrivial_common_embedding_impl | |
| 50 | : has_common_embedding_impl<Concept, T, U> | |
| 51 | { }; | |
| 52 | ||
| 53 | template <template <typename...> class Concept, typename T> | |
| 54 | struct has_nontrivial_common_embedding_impl<Concept, T, T> | |
| 55 | : std::false_type | |
| 56 | { }; | |
| 57 | ||
| 58 | //! @ingroup group-details | |
| 59 | //! Returns whether `T` and `U` are distinct and both have an embedding | |
| 60 | //! into a common type. | |
| 61 | //! | |
| 62 | //! If `T` and `U` do not have a common-type, this metafunction returns | |
| 63 | //! false. | |
| 64 | template <template <typename...> class Concept, typename T, typename U> | |
| 65 | using has_nontrivial_common_embedding = | |
| 66 | typename has_nontrivial_common_embedding_impl<Concept, T, U>::type; | |
| 67 | } BOOST_HANA_NAMESPACE_END | |
| 68 | ||
| 69 | #endif // !BOOST_HANA_DETAIL_HAS_COMMON_EMBEDDING_HPP |