boost/hana/tuple.hpp
/*! @file Defines `boost::hana::tuple`. Copyright Louis Dionne 2013-2022 Copyright Jason Rice 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_TUPLE_HPP #define BOOST_HANA_TUPLE_HPP #include <boost/hana/fwd/tuple.hpp> #include <boost/hana/basic_tuple.hpp> #include <boost/hana/bool.hpp> #include <boost/hana/config.hpp> #include <boost/hana/detail/decay.hpp> #include <boost/hana/detail/fast_and.hpp> #include <boost/hana/detail/index_if.hpp> #include <boost/hana/detail/intrinsics.hpp> #include <boost/hana/detail/operators/adl.hpp> #include <boost/hana/detail/operators/comparable.hpp> #include <boost/hana/detail/operators/iterable.hpp> #include <boost/hana/detail/operators/monad.hpp> #include <boost/hana/detail/operators/orderable.hpp> #include <boost/hana/fwd/at.hpp> #include <boost/hana/fwd/core/make.hpp> #include <boost/hana/fwd/drop_front.hpp> #include <boost/hana/fwd/index_if.hpp> #include <boost/hana/fwd/is_empty.hpp> #include <boost/hana/fwd/length.hpp> #include <boost/hana/fwd/optional.hpp> #include <boost/hana/fwd/unpack.hpp> #include <boost/hana/type.hpp> // required by fwd decl of tuple_t #include <cstddef> #include <type_traits> #include <utility> namespace boost { namespace hana { namespace detail { template <typename Xs, typename Ys, std::size_t ...n> constexpr void assign(Xs& xs, Ys&& ys, std::index_sequence<n...>) { int sequence[] = {int{}, ((void)( hana::at_c<n>(xs) = hana::at_c<n>(static_cast<Ys&&>(ys)) ), int{})...}; (void)sequence; } struct from_index_sequence_t { }; template <typename Tuple, typename ...Yn> struct is_same_tuple : std::false_type { }; template <typename Tuple> struct is_same_tuple<typename detail::decay<Tuple>::type, Tuple> : std::true_type { }; template <bool SameTuple, bool SameNumberOfElements, typename Tuple, typename ...Yn> struct enable_tuple_variadic_ctor; template <typename ...Xn, typename ...Yn> struct enable_tuple_variadic_ctor<false, true, hana::tuple<Xn...>, Yn...> : std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Yn&&)...>::value > { }; } ////////////////////////////////////////////////////////////////////////// // tuple ////////////////////////////////////////////////////////////////////////// template <> #ifdef BOOST_HANA_WORKAROUND_MSVC_EMPTYBASE struct __declspec(empty_bases) tuple<> final #else struct tuple<> final #endif : detail::operators::adl<tuple<>> , detail::iterable_operators<tuple<>> { constexpr tuple() { } using hana_tag = tuple_tag; }; template <typename ...Xn> #ifdef BOOST_HANA_WORKAROUND_MSVC_EMPTYBASE struct __declspec(empty_bases) tuple final #else struct tuple final #endif : detail::operators::adl<tuple<Xn...>> , detail::iterable_operators<tuple<Xn...>> { basic_tuple<Xn...> storage_; using hana_tag = tuple_tag; private: template <typename Other, std::size_t ...n> explicit constexpr tuple(detail::from_index_sequence_t, std::index_sequence<n...>, Other&& other) : storage_(hana::at_c<n>(static_cast<Other&&>(other))...) { } public: template <typename ...dummy, typename = typename std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, dummy...)...>::value >::type> constexpr tuple() : storage_() { } template <typename ...dummy, typename = typename std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Xn const&, dummy...)...>::value >::type> constexpr tuple(Xn const& ...xn) : storage_(xn...) { } template <typename ...Yn, typename = typename detail::enable_tuple_variadic_ctor< detail::is_same_tuple<tuple, Yn...>::value, sizeof...(Xn) == sizeof...(Yn), tuple, Yn... >::type> constexpr tuple(Yn&& ...yn) : storage_(static_cast<Yn&&>(yn)...) { } template <typename ...Yn, typename = typename std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Yn const&)...>::value >::type> constexpr tuple(tuple<Yn...> const& other) : tuple(detail::from_index_sequence_t{}, std::make_index_sequence<sizeof...(Xn)>{}, other.storage_) { } template <typename ...Yn, typename = typename std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Yn&&)...>::value >::type> constexpr tuple(tuple<Yn...>&& other) : tuple(detail::from_index_sequence_t{}, std::make_index_sequence<sizeof...(Xn)>{}, static_cast<tuple<Yn...>&&>(other).storage_) { } // The three following constructors are required to make sure that // the tuple(Yn&&...) constructor is _not_ preferred over the copy // constructor for unary tuples containing a type that is constructible // from tuple<...>. See test/tuple/cnstr.trap.cpp template <typename ...dummy, typename = typename std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Xn const&, dummy...)...>::value >::type> constexpr tuple(tuple const& other) : tuple(detail::from_index_sequence_t{}, std::make_index_sequence<sizeof...(Xn)>{}, other.storage_) { } template <typename ...dummy, typename = typename std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Xn const&, dummy...)...>::value >::type> constexpr tuple(tuple& other) : tuple(const_cast<tuple const&>(other)) { } template <typename ...dummy, typename = typename std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Xn&&, dummy...)...>::value >::type> constexpr tuple(tuple&& other) : tuple(detail::from_index_sequence_t{}, std::make_index_sequence<sizeof...(Xn)>{}, static_cast<tuple&&>(other).storage_) { } template <typename ...Yn, typename = typename std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_ASSIGNABLE(Xn&, Yn const&)...>::value >::type> constexpr tuple& operator=(tuple<Yn...> const& other) { detail::assign(this->storage_, other.storage_, std::make_index_sequence<sizeof...(Xn)>{}); return *this; } template <typename ...Yn, typename = typename std::enable_if< detail::fast_and<BOOST_HANA_TT_IS_ASSIGNABLE(Xn&, Yn&&)...>::value >::type> constexpr tuple& operator=(tuple<Yn...>&& other) { detail::assign(this->storage_, static_cast<tuple<Yn...>&&>(other).storage_, std::make_index_sequence<sizeof...(Xn)>{}); return *this; } }; ////////////////////////////////////////////////////////////////////////// // Operators ////////////////////////////////////////////////////////////////////////// namespace detail { template <> struct comparable_operators<tuple_tag> { static constexpr bool value = true; }; template <> struct orderable_operators<tuple_tag> { static constexpr bool value = true; }; template <> struct monad_operators<tuple_tag> { static constexpr bool value = true; }; } ////////////////////////////////////////////////////////////////////////// // Foldable ////////////////////////////////////////////////////////////////////////// template <> struct unpack_impl<tuple_tag> { template <typename F> static constexpr decltype(auto) apply(tuple<>&&, F&& f) { return static_cast<F&&>(f)(); } template <typename F> static constexpr decltype(auto) apply(tuple<>&, F&& f) { return static_cast<F&&>(f)(); } template <typename F> static constexpr decltype(auto) apply(tuple<> const&, F&& f) { return static_cast<F&&>(f)(); } template <typename Xs, typename F> static constexpr decltype(auto) apply(Xs&& xs, F&& f) { return hana::unpack(static_cast<Xs&&>(xs).storage_, static_cast<F&&>(f)); } }; template <> struct length_impl<tuple_tag> { template <typename ...Xs> static constexpr auto apply(tuple<Xs...> const&) { return hana::size_c<sizeof...(Xs)>; } }; ////////////////////////////////////////////////////////////////////////// // Iterable ////////////////////////////////////////////////////////////////////////// template <> struct at_impl<tuple_tag> { template <typename Xs, typename N> static constexpr decltype(auto) apply(Xs&& xs, N const&) { constexpr std::size_t index = N::value; return hana::at_c<index>(static_cast<Xs&&>(xs).storage_); } }; template <> struct drop_front_impl<tuple_tag> { template <std::size_t N, typename Xs, std::size_t ...i> static constexpr auto helper(Xs&& xs, std::index_sequence<i...>) { return hana::make<tuple_tag>(hana::at_c<i+N>(static_cast<Xs&&>(xs))...); } template <typename Xs, typename N> static constexpr auto apply(Xs&& xs, N const&) { constexpr std::size_t len = decltype(hana::length(xs))::value; return helper<N::value>(static_cast<Xs&&>(xs), std::make_index_sequence< (N::value < len) ? len - N::value : 0 >{}); } }; template <> struct is_empty_impl<tuple_tag> { template <typename ...Xs> static constexpr auto apply(tuple<Xs...> const&) { return hana::bool_c<sizeof...(Xs) == 0>; } }; // compile-time optimizations (to reduce the # of function instantiations) template <std::size_t n, typename ...Xs> constexpr decltype(auto) at_c(tuple<Xs...> const& xs) { return hana::at_c<n>(xs.storage_); } template <std::size_t n, typename ...Xs> constexpr decltype(auto) at_c(tuple<Xs...>& xs) { return hana::at_c<n>(xs.storage_); } template <std::size_t n, typename ...Xs> constexpr decltype(auto) at_c(tuple<Xs...>&& xs) { return hana::at_c<n>(static_cast<tuple<Xs...>&&>(xs).storage_); } template <> struct index_if_impl<tuple_tag> { template <typename ...Xs, typename Pred> static constexpr auto apply(tuple<Xs...> const&, Pred const&) -> typename detail::index_if<Pred, Xs...>::type { return {}; } }; ////////////////////////////////////////////////////////////////////////// // Sequence ////////////////////////////////////////////////////////////////////////// template <> struct Sequence<tuple_tag> { static constexpr bool value = true; }; template <> struct make_impl<tuple_tag> { template <typename ...Xs> static constexpr tuple<typename detail::decay<Xs>::type...> apply(Xs&& ...xs) { return {static_cast<Xs&&>(xs)...}; } }; }} // end namespace boost::hana #endif // !BOOST_HANA_TUPLE_HPP