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Diffstat (limited to 'boost/hana/ext/std/tuple.hpp')
| -rw-r--r-- | boost/hana/ext/std/tuple.hpp | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/boost/hana/ext/std/tuple.hpp b/boost/hana/ext/std/tuple.hpp new file mode 100644 index 0000000000..b2e95d7f30 --- /dev/null +++ b/boost/hana/ext/std/tuple.hpp @@ -0,0 +1,190 @@ +/*! +@file +Adapts `std::tuple` for use with Hana. + +@copyright Louis Dionne 2013-2016 +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_EXT_STD_TUPLE_HPP +#define BOOST_HANA_EXT_STD_TUPLE_HPP + +#include <boost/hana/bool.hpp> +#include <boost/hana/config.hpp> +#include <boost/hana/fwd/at.hpp> +#include <boost/hana/fwd/core/make.hpp> +#include <boost/hana/fwd/core/tag_of.hpp> +#include <boost/hana/fwd/drop_front.hpp> +#include <boost/hana/fwd/empty.hpp> +#include <boost/hana/fwd/flatten.hpp> +#include <boost/hana/fwd/front.hpp> +#include <boost/hana/fwd/is_empty.hpp> +#include <boost/hana/fwd/length.hpp> +#include <boost/hana/fwd/lift.hpp> +#include <boost/hana/integral_constant.hpp> + +#include <cstddef> +#include <tuple> +#include <type_traits> +#include <utility> + + +#ifdef BOOST_HANA_CONFIG_HAS_NO_STD_TUPLE_ADAPTER +# error The adapter for std::tuple is not supported with versions of \ + libc++ prior to the one shipped with Clang 3.7 because of a bug \ + in the tuple implementation. +#endif + + +#ifdef BOOST_HANA_DOXYGEN_INVOKED +namespace std { + //! @ingroup group-ext-std + //! Adapter for `std::tuple`s. + //! + //! + //! Modeled concepts + //! ---------------- + //! A `std::tuple` is a model of the `Sequence` concept, and all the + //! concepts it refines. That makes it essentially the same as a Hana + //! tuple, although the complexity of some operations might differ from + //! that of Hana's tuple. + //! + //! @include example/ext/std/tuple.cpp + template <typename ...T> + struct tuple { }; +} +#endif + + +BOOST_HANA_NAMESPACE_BEGIN + namespace ext { namespace std { struct tuple_tag; }} + + template <typename ...Xs> + struct tag_of<std::tuple<Xs...>> { + using type = ext::std::tuple_tag; + }; + + ////////////////////////////////////////////////////////////////////////// + // make + ////////////////////////////////////////////////////////////////////////// + template <> + struct make_impl<ext::std::tuple_tag> { + template <typename ...Xs> + static constexpr decltype(auto) apply(Xs&& ...xs) { + return std::make_tuple(static_cast<Xs&&>(xs)...); + } + }; + + ////////////////////////////////////////////////////////////////////////// + // Applicative + ////////////////////////////////////////////////////////////////////////// + template <> + struct lift_impl<ext::std::tuple_tag> { + template <typename X> + static constexpr auto apply(X&& x) { + return std::tuple<typename std::decay<X>::type>{ + static_cast<X&&>(x)}; + } + }; + + ////////////////////////////////////////////////////////////////////////// + // Monad + ////////////////////////////////////////////////////////////////////////// + template <> + struct flatten_impl<ext::std::tuple_tag> { + template <typename Xs, std::size_t ...i> + static constexpr decltype(auto) + flatten_helper(Xs&& xs, std::index_sequence<i...>) { +#if defined(BOOST_HANA_CONFIG_LIBCPP_HAS_BUG_22806) + return std::tuple_cat(std::get<i>(xs)...); +#else + return std::tuple_cat(std::get<i>(static_cast<Xs&&>(xs))...); +#endif + } + + template <typename Xs> + static constexpr decltype(auto) apply(Xs&& xs) { + using Raw = typename std::remove_reference<Xs>::type; + constexpr std::size_t Length = std::tuple_size<Raw>::value; + return flatten_helper(static_cast<Xs&&>(xs), + std::make_index_sequence<Length>{}); + } + }; + + ////////////////////////////////////////////////////////////////////////// + // MonadPlus + ////////////////////////////////////////////////////////////////////////// + template <> + struct empty_impl<ext::std::tuple_tag> { + static constexpr auto apply() + { return std::tuple<>{}; } + }; + + ////////////////////////////////////////////////////////////////////////// + // Iterable + ////////////////////////////////////////////////////////////////////////// + template <> + struct front_impl<ext::std::tuple_tag> { + template <typename Xs> + static constexpr decltype(auto) apply(Xs&& xs) { + return std::get<0>(static_cast<Xs&&>(xs)); + } + }; + + template <> + struct drop_front_impl<ext::std::tuple_tag> { + template <std::size_t n, typename Xs, std::size_t ...i> + static constexpr auto drop_front_helper(Xs&& xs, std::index_sequence<i...>) { + return std::make_tuple( + hana::at_c<n + i>(static_cast<Xs&&>(xs))... + ); + } + + template <typename Xs, typename N> + static constexpr auto apply(Xs&& xs, N const&) { + using Raw = typename std::remove_reference<Xs>::type; + constexpr std::size_t n = N::value; + constexpr auto len = std::tuple_size<Raw>::value; + return drop_front_helper<n>(static_cast<Xs&&>(xs), + std::make_index_sequence<(n < len ? len - n : 0)>{}); + } + }; + + template <> + struct is_empty_impl<ext::std::tuple_tag> { + template <typename ...Xs> + static constexpr auto apply(std::tuple<Xs...> const&) + { return hana::bool_c<sizeof...(Xs) == 0>; } + }; + + template <> + struct at_impl<ext::std::tuple_tag> { + template <typename Xs, typename N> + static constexpr decltype(auto) apply(Xs&& xs, N const&) { + constexpr std::size_t index = N::value; + return std::get<index>(static_cast<Xs&&>(xs)); + } + }; + + ////////////////////////////////////////////////////////////////////////// + // Foldable + ////////////////////////////////////////////////////////////////////////// + template <> + struct length_impl<ext::std::tuple_tag> { + template <typename ...Xs> + static constexpr auto apply(std::tuple<Xs...> const&) { + return hana::size_c<sizeof...(Xs)>; + } + }; + + ////////////////////////////////////////////////////////////////////////// + // Sequence + ////////////////////////////////////////////////////////////////////////// + template <> + struct Sequence<ext::std::tuple_tag> { + static constexpr bool value = true; + }; +BOOST_HANA_NAMESPACE_END + +#endif // !BOOST_HANA_EXT_STD_TUPLE_HPP |