306 lines
11 KiB
C++
306 lines
11 KiB
C++
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/*!
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@file
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Defines `boost::hana::tuple`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_TUPLE_HPP
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#define BOOST_HANA_TUPLE_HPP
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#include <boost/hana/fwd/tuple.hpp>
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#include <boost/hana/basic_tuple.hpp>
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#include <boost/hana/bool.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/detail/decay.hpp>
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#include <boost/hana/detail/fast_and.hpp>
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#include <boost/hana/detail/index_if.hpp>
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#include <boost/hana/detail/intrinsics.hpp>
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#include <boost/hana/detail/operators/adl.hpp>
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#include <boost/hana/detail/operators/comparable.hpp>
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#include <boost/hana/detail/operators/iterable.hpp>
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#include <boost/hana/detail/operators/monad.hpp>
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#include <boost/hana/detail/operators/orderable.hpp>
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#include <boost/hana/fwd/at.hpp>
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#include <boost/hana/fwd/core/make.hpp>
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#include <boost/hana/fwd/drop_front.hpp>
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#include <boost/hana/fwd/find_if.hpp>
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#include <boost/hana/fwd/is_empty.hpp>
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#include <boost/hana/fwd/length.hpp>
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#include <boost/hana/fwd/optional.hpp>
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#include <boost/hana/fwd/unpack.hpp>
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#include <boost/hana/type.hpp> // required by fwd decl of tuple_t
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#include <cstddef>
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#include <type_traits>
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#include <utility>
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BOOST_HANA_NAMESPACE_BEGIN
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namespace detail {
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template <typename Xs, typename Ys, std::size_t ...n>
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constexpr void assign(Xs& xs, Ys&& ys, std::index_sequence<n...>) {
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int sequence[] = {int{}, ((void)(
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hana::get_impl<n>(xs) = hana::get_impl<n>(static_cast<Ys&&>(ys))
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), int{})...};
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(void)sequence;
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}
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struct from_index_sequence_t { };
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}
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//////////////////////////////////////////////////////////////////////////
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// tuple
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//////////////////////////////////////////////////////////////////////////
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template <>
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struct tuple<>
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: detail::operators::adl<tuple<>>
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, detail::iterable_operators<tuple<>>
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{
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constexpr tuple() { }
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using hana_tag = tuple_tag;
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};
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template <typename ...Xn>
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struct tuple
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: detail::operators::adl<tuple<Xn...>>
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, detail::iterable_operators<tuple<Xn...>>
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{
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basic_tuple<Xn...> storage_;
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using hana_tag = tuple_tag;
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private:
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template <typename Other, std::size_t ...n>
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explicit constexpr tuple(detail::from_index_sequence_t, std::index_sequence<n...>, Other&& other)
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: storage_(hana::get_impl<n>(static_cast<Other&&>(other))...)
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{ }
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public:
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template <typename ...dummy, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, dummy...)...>::value
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>::type>
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constexpr tuple()
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: storage_()
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{ }
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template <typename ...dummy, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Xn const&, dummy...)...>::value
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>::type>
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constexpr tuple(Xn const& ...xn)
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: storage_(xn...)
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{ }
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template <typename ...Yn, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Yn&&)...>::value
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>::type>
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constexpr tuple(Yn&& ...yn)
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: storage_(static_cast<Yn&&>(yn)...)
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{ }
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template <typename ...Yn, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Yn const&)...>::value
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>::type>
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constexpr tuple(tuple<Yn...> const& other)
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: tuple(detail::from_index_sequence_t{},
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std::make_index_sequence<sizeof...(Xn)>{},
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other.storage_)
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{ }
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template <typename ...Yn, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Yn&&)...>::value
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>::type>
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constexpr tuple(tuple<Yn...>&& other)
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: tuple(detail::from_index_sequence_t{},
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std::make_index_sequence<sizeof...(Xn)>{},
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static_cast<tuple<Yn...>&&>(other).storage_)
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{ }
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// The three following constructors are required to make sure that
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// the tuple(Yn&&...) constructor is _not_ preferred over the copy
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// constructor for unary tuples containing a type that is constructible
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// from tuple<...>. See test/tuple/trap_construct.cpp
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template <typename ...dummy, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Xn const&, dummy...)...>::value
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>::type>
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constexpr tuple(tuple const& other)
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: tuple(detail::from_index_sequence_t{},
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std::make_index_sequence<sizeof...(Xn)>{},
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other.storage_)
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{ }
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template <typename ...dummy, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Xn const&, dummy...)...>::value
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>::type>
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constexpr tuple(tuple& other)
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: tuple(const_cast<tuple const&>(other))
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{ }
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template <typename ...dummy, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_CONSTRUCTIBLE(Xn, Xn&&, dummy...)...>::value
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>::type>
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constexpr tuple(tuple&& other)
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: tuple(detail::from_index_sequence_t{},
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std::make_index_sequence<sizeof...(Xn)>{},
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static_cast<tuple&&>(other).storage_)
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{ }
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template <typename ...Yn, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_ASSIGNABLE(Xn&, Yn const&)...>::value
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>::type>
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constexpr tuple& operator=(tuple<Yn...> const& other) {
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detail::assign(this->storage_, other.storage_,
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std::make_index_sequence<sizeof...(Xn)>{});
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return *this;
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}
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template <typename ...Yn, typename = typename std::enable_if<
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detail::fast_and<BOOST_HANA_TT_IS_ASSIGNABLE(Xn&, Yn&&)...>::value
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>::type>
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constexpr tuple& operator=(tuple<Yn...>&& other) {
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detail::assign(this->storage_, static_cast<tuple<Yn...>&&>(other).storage_,
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std::make_index_sequence<sizeof...(Xn)>{});
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return *this;
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}
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};
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//////////////////////////////////////////////////////////////////////////
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// Operators
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//////////////////////////////////////////////////////////////////////////
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namespace detail {
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template <>
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struct comparable_operators<tuple_tag> {
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static constexpr bool value = true;
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};
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template <>
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struct orderable_operators<tuple_tag> {
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static constexpr bool value = true;
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};
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template <>
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struct monad_operators<tuple_tag> {
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static constexpr bool value = true;
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};
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}
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//////////////////////////////////////////////////////////////////////////
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// Foldable
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//////////////////////////////////////////////////////////////////////////
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template <>
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struct unpack_impl<tuple_tag> {
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template <typename F>
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static constexpr decltype(auto) apply(tuple<>&&, F&& f)
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{ return static_cast<F&&>(f)(); }
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template <typename F>
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static constexpr decltype(auto) apply(tuple<>&, F&& f)
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{ return static_cast<F&&>(f)(); }
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template <typename F>
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static constexpr decltype(auto) apply(tuple<> const&, F&& f)
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{ return static_cast<F&&>(f)(); }
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template <typename Xs, typename F>
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static constexpr decltype(auto) apply(Xs&& xs, F&& f) {
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return hana::unpack(static_cast<Xs&&>(xs).storage_, static_cast<F&&>(f));
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}
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};
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template <>
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struct length_impl<tuple_tag> {
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template <typename ...Xs>
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static constexpr auto apply(tuple<Xs...> const&)
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{ return hana::size_c<sizeof...(Xs)>; }
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};
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//////////////////////////////////////////////////////////////////////////
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// Iterable
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//////////////////////////////////////////////////////////////////////////
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template <>
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struct at_impl<tuple_tag> {
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template <typename Xs, typename N>
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static constexpr decltype(auto) apply(Xs&& xs, N const&) {
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constexpr std::size_t index = N::value;
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return hana::get_impl<index>(static_cast<Xs&&>(xs).storage_);
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}
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};
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template <>
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struct drop_front_impl<tuple_tag> {
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template <std::size_t N, typename Xs, std::size_t ...i>
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static constexpr auto helper(Xs&& xs, std::index_sequence<i...>) {
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return hana::make<tuple_tag>(hana::at_c<i+N>(static_cast<Xs&&>(xs))...);
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}
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template <typename Xs, typename N>
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static constexpr auto apply(Xs&& xs, N const&) {
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constexpr std::size_t len = decltype(hana::length(xs))::value;
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return helper<N::value>(static_cast<Xs&&>(xs), std::make_index_sequence<
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N::value < len ? len - N::value : 0
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>{});
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}
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};
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template <>
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struct is_empty_impl<tuple_tag> {
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template <typename ...Xs>
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static constexpr auto apply(tuple<Xs...> const&)
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{ return hana::bool_c<sizeof...(Xs) == 0>; }
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};
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// compile-time optimizations (to reduce the # of function instantiations)
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template <std::size_t n, typename ...Xs>
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constexpr decltype(auto) at_c(tuple<Xs...> const& xs) {
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return hana::get_impl<n>(xs.storage_);
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}
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template <std::size_t n, typename ...Xs>
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constexpr decltype(auto) at_c(tuple<Xs...>& xs) {
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return hana::get_impl<n>(xs.storage_);
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}
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template <std::size_t n, typename ...Xs>
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constexpr decltype(auto) at_c(tuple<Xs...>&& xs) {
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return hana::get_impl<n>(static_cast<tuple<Xs...>&&>(xs).storage_);
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}
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//////////////////////////////////////////////////////////////////////////
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// Sequence
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//////////////////////////////////////////////////////////////////////////
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template <>
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struct Sequence<tuple_tag> {
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static constexpr bool value = true;
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};
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template <>
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struct make_impl<tuple_tag> {
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template <typename ...Xs>
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static constexpr
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tuple<typename detail::decay<Xs>::type...> apply(Xs&& ...xs)
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{ return {static_cast<Xs&&>(xs)...}; }
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};
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template <>
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struct find_if_impl<tuple_tag> {
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template <std::size_t index, typename Xs>
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static constexpr auto helper(Xs&&, hana::true_) {
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return hana::nothing;
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}
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template <std::size_t index, typename Xs>
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static constexpr auto helper(Xs&& xs, hana::false_) {
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return hana::just(hana::at_c<index>(static_cast<Xs&&>(xs)));
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}
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template <typename Xs, typename Pred>
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static constexpr auto apply(Xs&& xs, Pred&&) {
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using Pack = typename detail::make_pack<Xs>::type;
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constexpr std::size_t index = detail::index_if<Pred&&, Pack>::value;
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constexpr std::size_t len = Pack::length;
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return helper<index>(static_cast<Xs&&>(xs), hana::bool_c<index == len>);
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_TUPLE_HPP
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