301 lines
10 KiB
C++
301 lines
10 KiB
C++
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/*!
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@file
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Defines `boost::hana::basic_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_BASIC_TUPLE_HPP
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#define BOOST_HANA_BASIC_TUPLE_HPP
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#include <boost/hana/fwd/basic_tuple.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/intrinsics.hpp>
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#include <boost/hana/fwd/at.hpp>
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#include <boost/hana/fwd/bool.hpp>
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#include <boost/hana/fwd/concept/sequence.hpp>
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#include <boost/hana/fwd/core/make.hpp>
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#include <boost/hana/fwd/core/tag_of.hpp>
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#include <boost/hana/fwd/drop_front.hpp>
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#include <boost/hana/fwd/is_empty.hpp>
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#include <boost/hana/fwd/transform.hpp>
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#include <boost/hana/fwd/unpack.hpp>
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#if 0 //! @todo Until we strip down headers, this includes too much
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#include <boost/hana/fwd/integral_constant.hpp>
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#include <boost/hana/fwd/length.hpp>
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#endif
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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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//////////////////////////////////////////////////////////////////////
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// elt<n, Xn>
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//
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// `elt` stands for `tuple_element`; the name is compressed to reduce
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// symbol lengths.
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//
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// Wrapper holding the actual elements of a tuple. It takes care of
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// optimizing the storage for empty types.
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//
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// When available, we use compiler intrinsics to reduce the number
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// of instantiations.
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//////////////////////////////////////////////////////////////////////
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template <std::size_t n, typename Xn, bool =
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BOOST_HANA_TT_IS_EMPTY(Xn) && !BOOST_HANA_TT_IS_FINAL(Xn)
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>
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struct elt;
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// Specialize storage for empty types
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template <std::size_t n, typename Xn>
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struct elt<n, Xn, true> : Xn {
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constexpr elt() = default;
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template <typename Yn>
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explicit constexpr elt(Yn&& yn)
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: Xn(static_cast<Yn&&>(yn))
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{ }
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};
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// Specialize storage for non-empty types
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template <std::size_t n, typename Xn>
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struct elt<n, Xn, false> {
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constexpr elt() = default;
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template <typename Yn>
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explicit constexpr elt(Yn&& yn)
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: data_(static_cast<Yn&&>(yn))
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{ }
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Xn data_;
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};
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}
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//////////////////////////////////////////////////////////////////////////
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// get_impl
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//////////////////////////////////////////////////////////////////////////
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template <std::size_t n, typename Xn>
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constexpr Xn const& get_impl(detail::elt<n, Xn, true> const& xn)
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{ return xn; }
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template <std::size_t n, typename Xn>
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constexpr Xn& get_impl(detail::elt<n, Xn, true>& xn)
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{ return xn; }
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template <std::size_t n, typename Xn>
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constexpr Xn&& get_impl(detail::elt<n, Xn, true>&& xn)
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{ return static_cast<Xn&&>(xn); }
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template <std::size_t n, typename Xn>
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constexpr Xn const& get_impl(detail::elt<n, Xn, false> const& xn)
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{ return xn.data_; }
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template <std::size_t n, typename Xn>
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constexpr Xn& get_impl(detail::elt<n, Xn, false>& xn)
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{ return xn.data_; }
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template <std::size_t n, typename Xn>
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constexpr Xn&& get_impl(detail::elt<n, Xn, false>&& xn)
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{ return static_cast<Xn&&>(xn.data_); }
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namespace detail {
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//////////////////////////////////////////////////////////////////////
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// basic_tuple_impl<n, Xn>
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//////////////////////////////////////////////////////////////////////
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struct from_other { };
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template <typename Indices, typename ...Xn>
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struct basic_tuple_impl;
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template <std::size_t ...n, typename ...Xn>
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struct basic_tuple_impl<std::index_sequence<n...>, Xn...>
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: detail::elt<n, Xn>...
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{
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static constexpr std::size_t size_ = sizeof...(Xn);
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constexpr basic_tuple_impl() = default;
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template <typename Other>
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explicit constexpr basic_tuple_impl(detail::from_other, Other&& other)
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: detail::elt<n, Xn>(get_impl<n>(static_cast<Other&&>(other)))...
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{ }
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template <typename ...Yn>
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explicit constexpr basic_tuple_impl(Yn&& ...yn)
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: detail::elt<n, Xn>(static_cast<Yn&&>(yn))...
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{ }
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};
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}
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//////////////////////////////////////////////////////////////////////////
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// basic_tuple
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//////////////////////////////////////////////////////////////////////////
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//! @cond
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template <typename ...Xn>
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struct basic_tuple final
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: detail::basic_tuple_impl<std::make_index_sequence<sizeof...(Xn)>, Xn...>
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{
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using Base = detail::basic_tuple_impl<std::make_index_sequence<sizeof...(Xn)>, Xn...>;
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constexpr basic_tuple() = default;
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// copy constructor
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template <typename Other, typename = typename std::enable_if<
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std::is_same<typename detail::decay<Other>::type, basic_tuple>::value
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>::type>
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constexpr basic_tuple(Other&& other)
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: Base(detail::from_other{}, static_cast<Other&&>(other))
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{ }
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template <typename ...Yn>
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explicit constexpr basic_tuple(Yn&& ...yn)
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: Base(static_cast<Yn&&>(yn)...)
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{ }
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};
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//! @endcond
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template <typename ...Xn>
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struct tag_of<basic_tuple<Xn...>> {
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using type = basic_tuple_tag;
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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<basic_tuple_tag> {
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template <std::size_t ...i, typename ...Xn, typename F>
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static constexpr decltype(auto)
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apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...> const& xs, F&& f) {
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return static_cast<F&&>(f)(
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get_impl<i>(static_cast<detail::elt<i, Xn> const&>(xs))...
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);
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}
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template <std::size_t ...i, typename ...Xn, typename F>
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static constexpr decltype(auto)
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apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...>& xs, F&& f) {
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return static_cast<F&&>(f)(
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get_impl<i>(static_cast<detail::elt<i, Xn>&>(xs))...
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);
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}
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template <std::size_t ...i, typename ...Xn, typename F>
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static constexpr decltype(auto)
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apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...>&& xs, F&& f) {
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return static_cast<F&&>(f)(
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get_impl<i>(static_cast<detail::elt<i, Xn>&&>(xs))...
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);
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}
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};
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//////////////////////////////////////////////////////////////////////////
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// Functor
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//////////////////////////////////////////////////////////////////////////
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template <>
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struct transform_impl<basic_tuple_tag> {
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template <std::size_t ...i, typename ...Xn, typename F>
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static constexpr auto
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apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...> const& xs, F const& f) {
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return hana::make_basic_tuple(
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f(get_impl<i>(static_cast<detail::elt<i, Xn> const&>(xs)))...
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);
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}
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template <std::size_t ...i, typename ...Xn, typename F>
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static constexpr auto
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apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...>& xs, F const& f) {
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return hana::make_basic_tuple(
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f(get_impl<i>(static_cast<detail::elt<i, Xn>&>(xs)))...
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);
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}
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template <std::size_t ...i, typename ...Xn, typename F>
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static constexpr auto
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apply(detail::basic_tuple_impl<std::index_sequence<i...>, Xn...>&& xs, F const& f) {
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return hana::make_basic_tuple(
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f(get_impl<i>(static_cast<detail::elt<i, Xn>&&>(xs)))...
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);
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}
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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<basic_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));
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}
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};
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template <>
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struct drop_front_impl<basic_tuple_tag> {
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template <std::size_t N, typename Xs, std::size_t ...i>
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static constexpr auto drop_front_helper(Xs&& xs, std::index_sequence<i...>) {
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return hana::make_basic_tuple(hana::get_impl<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 = detail::decay<Xs>::type::size_;
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return drop_front_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<basic_tuple_tag> {
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template <typename ...Xs>
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static constexpr hana::bool_<sizeof...(Xs) == 0>
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apply(basic_tuple<Xs...> const&)
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{ return {}; }
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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<basic_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<basic_tuple_tag> {
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template <typename ...Xn>
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static constexpr basic_tuple<typename detail::decay<Xn>::type...>
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apply(Xn&& ...xn) {
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return basic_tuple<typename detail::decay<Xn>::type...>{
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static_cast<Xn&&>(xn)...
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};
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}
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};
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#if 0
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//////////////////////////////////////////////////////////////////////////
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// length
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//////////////////////////////////////////////////////////////////////////
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template <>
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struct length_impl<basic_tuple_tag> {
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template <typename ...Xn>
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static constexpr auto apply(basic_tuple<Xn...> const&) {
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return hana::size_c<sizeof...(Xn)>;
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}
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};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_BASIC_TUPLE_HPP
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