projects / ceph.git / blame
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1 | /*! |
| 2 | @file | |
| 3 | Defines `boost::hana::basic_tuple`. | |
| 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_BASIC_TUPLE_HPP | |
| 11 | #define BOOST_HANA_BASIC_TUPLE_HPP | |
| 12 | ||
| 13 | #include <boost/hana/fwd/basic_tuple.hpp> | |
| 14 | ||
| 15 | #include <boost/hana/config.hpp> | |
| 16 | #include <boost/hana/detail/decay.hpp> | |
| 17 | #include <boost/hana/detail/intrinsics.hpp> | |
| 18 | #include <boost/hana/fwd/at.hpp> | |
| 19 | #include <boost/hana/fwd/bool.hpp> | |
| 20 | #include <boost/hana/fwd/concept/sequence.hpp> | |
| 21 | #include <boost/hana/fwd/core/make.hpp> | |
| 22 | #include <boost/hana/fwd/core/tag_of.hpp> | |
| 23 | #include <boost/hana/fwd/drop_front.hpp> | |
| 24 | #include <boost/hana/fwd/is_empty.hpp> | |
| 25 | #include <boost/hana/fwd/transform.hpp> | |
| 26 | #include <boost/hana/fwd/unpack.hpp> | |
| 27 | ||
| 28 | #if 0 //! @todo Until we strip down headers, this includes too much | |
| 29 | #include <boost/hana/fwd/integral_constant.hpp> | |
| 30 | #include <boost/hana/fwd/length.hpp> | |
| 31 | #endif | |
| 32 | ||
| 33 | #include <cstddef> | |
| 34 | #include <type_traits> | |
| 35 | #include <utility> | |
| 36 | ||
| 37 | ||
| 38 | BOOST_HANA_NAMESPACE_BEGIN | |
| 39 | namespace detail { | |
| 40 | ////////////////////////////////////////////////////////////////////// | |
| 41 | // elt<n, Xn> | |
| 42 | // | |
| 43 | // `elt` stands for `tuple_element`; the name is compressed to reduce | |
| 44 | // symbol lengths. | |
| 45 | // | |
| 46 | // Wrapper holding the actual elements of a tuple. It takes care of | |
| 47 | // optimizing the storage for empty types. | |
| 48 | // | |
| 49 | // When available, we use compiler intrinsics to reduce the number | |
| 50 | // of instantiations. | |
| 51 | ////////////////////////////////////////////////////////////////////// | |
| 52 | template <std::size_t n, typename Xn, bool = | |
| 53 | BOOST_HANA_TT_IS_EMPTY(Xn) && !BOOST_HANA_TT_IS_FINAL(Xn) | |
| 54 | > | |
| 55 | struct elt; | |
| 56 | ||
| 57 | // Specialize storage for empty types | |
| 58 | template <std::size_t n, typename Xn> | |
| 59 | struct elt<n, Xn, true> : Xn { | |
| 60 | constexpr elt() = default; | |
| 61 | ||
| 62 | template <typename Yn> | |
| 63 | explicit constexpr elt(Yn&& yn) | |
| 64 | : Xn(static_cast<Yn&&>(yn)) | |
| 65 | { } | |
| 66 | }; | |
| 67 | ||
| 68 | // Specialize storage for non-empty types | |
| 69 | template <std::size_t n, typename Xn> | |
| 70 | struct elt<n, Xn, false> { | |
| 71 | constexpr elt() = default; | |
| 72 | ||
| 73 | template <typename Yn> | |
| 74 | explicit constexpr elt(Yn&& yn) | |
| 75 | : data_(static_cast<Yn&&>(yn)) | |
| 76 | { } | |
| 77 | ||
| 78 | Xn data_; | |
| 79 | }; | |
| 80 | } | |
| 81 | ||
| 82 | ////////////////////////////////////////////////////////////////////////// | |
| 83 | // get_impl | |
| 84 | ////////////////////////////////////////////////////////////////////////// | |
| 85 | template <std::size_t n, typename Xn> | |
| 86 | constexpr Xn const& get_impl(detail::elt<n, Xn, true> const& xn) | |
| 87 | { return xn; } | |
| 88 | ||
| 89 | template <std::size_t n, typename Xn> | |
| 90 | constexpr Xn& get_impl(detail::elt<n, Xn, true>& xn) | |
| 91 | { return xn; } | |
| 92 | ||
| 93 | template <std::size_t n, typename Xn> | |
| 94 | constexpr Xn&& get_impl(detail::elt<n, Xn, true>&& xn) | |
| 95 | { return static_cast<Xn&&>(xn); } | |
| 96 | ||
| 97 | ||
| 98 | template <std::size_t n, typename Xn> | |
| 99 | constexpr Xn const& get_impl(detail::elt<n, Xn, false> const& xn) | |
| 100 | { return xn.data_; } | |
| 101 | ||
| 102 | template <std::size_t n, typename Xn> | |
| 103 | constexpr Xn& get_impl(detail::elt<n, Xn, false>& xn) | |
| 104 | { return xn.data_; } | |
| 105 | ||
| 106 | template <std::size_t n, typename Xn> | |
| 107 | constexpr Xn&& get_impl(detail::elt<n, Xn, false>&& xn) | |
| 108 | { return static_cast<Xn&&>(xn.data_); } | |
| 109 | ||
| 110 | namespace detail { | |
| 111 | ////////////////////////////////////////////////////////////////////// | |
| 112 | // basic_tuple_impl<n, Xn> | |
| 113 | ////////////////////////////////////////////////////////////////////// | |
| 114 | struct from_other { }; | |
| 115 | ||
| 116 | template <typename Indices, typename ...Xn> | |
| 117 | struct basic_tuple_impl; | |
| 118 | ||
| 119 | template <std::size_t ...n, typename ...Xn> | |
| 120 | struct basic_tuple_impl<std::index_sequence<n...>, Xn...> | |
| 121 | : detail::elt<n, Xn>... | |
| 122 | { | |
| 123 | static constexpr std::size_t size_ = sizeof...(Xn); | |
| 124 | ||
| 125 | constexpr basic_tuple_impl() = default; | |
| 126 | ||
| 127 | template <typename Other> | |
| 128 | explicit constexpr basic_tuple_impl(detail::from_other, Other&& other) | |
| 129 | : detail::elt<n, Xn>(get_impl<n>(static_cast<Other&&>(other)))... | |
| 130 | { } | |
| 131 | ||
| 132 | template <typename ...Yn> | |
| 133 | explicit constexpr basic_tuple_impl(Yn&& ...yn) | |
| 134 | : detail::elt<n, Xn>(static_cast<Yn&&>(yn))... | |
| 135 | { } | |
| 136 | }; | |
| 137 | } | |
| 138 | ||
| 139 | ////////////////////////////////////////////////////////////////////////// | |
| 140 | // basic_tuple | |
| 141 | ////////////////////////////////////////////////////////////////////////// | |
| 142 | //! @cond | |
| 143 | template <typename ...Xn> | |
| 144 | struct basic_tuple final | |
| 145 | : detail::basic_tuple_impl<std::make_index_sequence<sizeof...(Xn)>, Xn...> | |
| 146 | { | |
| 147 | using Base = detail::basic_tuple_impl<std::make_index_sequence<sizeof...(Xn)>, Xn...>; | |
| 148 | ||
| 149 | constexpr basic_tuple() = default; | |
| 150 | ||
| 151 | // copy constructor | |
| 152 | template <typename Other, typename = typename std::enable_if< | |
| 153 | std::is_same<typename detail::decay<Other>::type, basic_tuple>::value | |
| 154 | >::type> | |
| 155 | constexpr basic_tuple(Other&& other) | |
| 156 | : Base(detail::from_other{}, static_cast<Other&&>(other)) | |
| 157 | { } | |
| 158 | ||
| 159 | template <typename ...Yn> | |
| 160 | explicit constexpr basic_tuple(Yn&& ...yn) | |
| 161 | : Base(static_cast<Yn&&>(yn)...) | |
| 162 | { } | |
| 163 | }; | |
| 164 | //! @endcond | |
| 165 | ||
| 166 | template <typename ...Xn> | |
| 167 | struct tag_of<basic_tuple<Xn...>> { | |
| 168 | using type = basic_tuple_tag; | |
| 169 | }; | |
| 170 | ||
| 171 | ////////////////////////////////////////////////////////////////////////// | |
| 172 | // Foldable | |
| 173 | ////////////////////////////////////////////////////////////////////////// | |
| 174 | template <> | |
| 175 | struct unpack_impl<basic_tuple_tag> { | |
| 176 | template <std::size_t ...i, typename ...Xn, typename F> | |
| 177 | static constexpr decltype(auto) | |
| 178 | apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...> const& xs, F&& f) { | |
| 179 | return static_cast<F&&>(f)( | |
| 180 | get_impl<i>(static_cast<detail::elt<i, Xn> const&>(xs))... | |
| 181 | ); | |
| 182 | } | |
| 183 | ||
| 184 | template <std::size_t ...i, typename ...Xn, typename F> | |
| 185 | static constexpr decltype(auto) | |
| 186 | apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...>& xs, F&& f) { | |
| 187 | return static_cast<F&&>(f)( | |
| 188 | get_impl<i>(static_cast<detail::elt<i, Xn>&>(xs))... | |
| 189 | ); | |
| 190 | } | |
| 191 | ||
| 192 | template <std::size_t ...i, typename ...Xn, typename F> | |
| 193 | static constexpr decltype(auto) | |
| 194 | apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...>&& xs, F&& f) { | |
| 195 | return static_cast<F&&>(f)( | |
| 196 | get_impl<i>(static_cast<detail::elt<i, Xn>&&>(xs))... | |
| 197 | ); | |
| 198 | } | |
| 199 | }; | |
| 200 | ||
| 201 | ////////////////////////////////////////////////////////////////////////// | |
| 202 | // Functor | |
| 203 | ////////////////////////////////////////////////////////////////////////// | |
| 204 | template <> | |
| 205 | struct transform_impl<basic_tuple_tag> { | |
| 206 | template <std::size_t ...i, typename ...Xn, typename F> | |
| 207 | static constexpr auto | |
| 208 | apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...> const& xs, F const& f) { | |
| 209 | return hana::make_basic_tuple( | |
| 210 | f(get_impl<i>(static_cast<detail::elt<i, Xn> const&>(xs)))... | |
| 211 | ); | |
| 212 | } | |
| 213 | ||
| 214 | template <std::size_t ...i, typename ...Xn, typename F> | |
| 215 | static constexpr auto | |
| 216 | apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...>& xs, F const& f) { | |
| 217 | return hana::make_basic_tuple( | |
| 218 | f(get_impl<i>(static_cast<detail::elt<i, Xn>&>(xs)))... | |
| 219 | ); | |
| 220 | } | |
| 221 | ||
| 222 | template <std::size_t ...i, typename ...Xn, typename F> | |
| 223 | static constexpr auto | |
| 224 | apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...>&& xs, F const& f) { | |
| 225 | return hana::make_basic_tuple( | |
| 226 | f(get_impl<i>(static_cast<detail::elt<i, Xn>&&>(xs)))... | |
| 227 | ); | |
| 228 | } | |
| 229 | }; | |
| 230 | ||
| 231 | ////////////////////////////////////////////////////////////////////////// | |
| 232 | // Iterable | |
| 233 | ////////////////////////////////////////////////////////////////////////// | |
| 234 | template <> | |
| 235 | struct at_impl<basic_tuple_tag> { | |
| 236 | template <typename Xs, typename N> | |
| 237 | static constexpr decltype(auto) apply(Xs&& xs, N const&) { | |
| 238 | constexpr std::size_t index = N::value; | |
| 239 | return hana::get_impl<index>(static_cast<Xs&&>(xs)); | |
| 240 | } | |
| 241 | }; | |
| 242 | ||
| 243 | template <> | |
| 244 | struct drop_front_impl<basic_tuple_tag> { | |
| 245 | template <std::size_t N, typename Xs, std::size_t ...i> | |
| 246 | static constexpr auto drop_front_helper(Xs&& xs, std::index_sequence<i...>) { | |
| 247 | return hana::make_basic_tuple(hana::get_impl<i+N>(static_cast<Xs&&>(xs))...); | |
| 248 | } | |
| 249 | ||
| 250 | template <typename Xs, typename N> | |
| 251 | static constexpr auto apply(Xs&& xs, N const&) { | |
| 252 | constexpr std::size_t len = detail::decay<Xs>::type::size_; | |
| 253 | return drop_front_helper<N::value>(static_cast<Xs&&>(xs), std::make_index_sequence< | |
| 254 | N::value < len ? len - N::value : 0 | |
| 255 | >{}); | |
| 256 | } | |
| 257 | }; | |
| 258 | ||
| 259 | template <> | |
| 260 | struct is_empty_impl<basic_tuple_tag> { | |
| 261 | template <typename ...Xs> | |
| 262 | static constexpr hana::bool_<sizeof...(Xs) == 0> | |
| 263 | apply(basic_tuple<Xs...> const&) | |
| 264 | { return {}; } | |
| 265 | }; | |
| 266 | ||
| 267 | ////////////////////////////////////////////////////////////////////////// | |
| 268 | // Sequence | |
| 269 | ////////////////////////////////////////////////////////////////////////// | |
| 270 | template <> | |
| 271 | struct Sequence<basic_tuple_tag> { | |
| 272 | static constexpr bool value = true; | |
| 273 | }; | |
| 274 | ||
| 275 | template <> | |
| 276 | struct make_impl<basic_tuple_tag> { | |
| 277 | template <typename ...Xn> | |
| 278 | static constexpr basic_tuple<typename detail::decay<Xn>::type...> | |
| 279 | apply(Xn&& ...xn) { | |
| 280 | return basic_tuple<typename detail::decay<Xn>::type...>{ | |
| 281 | static_cast<Xn&&>(xn)... | |
| 282 | }; | |
| 283 | } | |
| 284 | }; | |
| 285 | ||
| 286 | #if 0 | |
| 287 | ////////////////////////////////////////////////////////////////////////// | |
| 288 | // length | |
| 289 | ////////////////////////////////////////////////////////////////////////// | |
| 290 | template <> | |
| 291 | struct length_impl<basic_tuple_tag> { | |
| 292 | template <typename ...Xn> | |
| 293 | static constexpr auto apply(basic_tuple<Xn...> const&) { | |
| 294 | return hana::size_c<sizeof...(Xn)>; | |
| 295 | } | |
| 296 | }; | |
| 297 | #endif | |
| 298 | BOOST_HANA_NAMESPACE_END | |
| 299 | ||
| 300 | #endif // !BOOST_HANA_BASIC_TUPLE_HPP |