projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | /*! |
| 2 | @file | |
| 3 | Defines `boost::hana::detail::variadic::at`. | |
| 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_DETAIL_VARIADIC_AT_HPP | |
| 11 | #define BOOST_HANA_DETAIL_VARIADIC_AT_HPP | |
| 12 | ||
| 13 | #include <boost/hana/config.hpp> | |
| 14 | ||
| 15 | #include <cstddef> | |
| 16 | #include <utility> | |
| 17 | ||
| 18 | ||
| 19 | BOOST_HANA_NAMESPACE_BEGIN namespace detail { namespace variadic { | |
| 20 | template <std::size_t n, typename = std::make_index_sequence<n>> | |
| 21 | struct at_type; | |
| 22 | ||
| 23 | template <std::size_t n, std::size_t ...ignore> | |
| 24 | struct at_type<n, std::index_sequence<ignore...>> { | |
| 25 | private: | |
| 26 | template <typename Nth> | |
| 27 | static constexpr auto go(decltype(ignore, (void*)0)..., Nth nth, ...) | |
| 28 | { return nth; } | |
| 29 | ||
| 30 | public: | |
| 31 | template <typename ...Xs> | |
| 32 | constexpr auto operator()(Xs ...xs) const | |
| 33 | { return *go(&xs...); } | |
| 34 | }; | |
| 35 | ||
| 36 | template <std::size_t n> | |
| 37 | constexpr at_type<n> at{}; | |
| 38 | }} BOOST_HANA_NAMESPACE_END | |
| 39 | ||
| 40 | #endif // !BOOST_HANA_DETAIL_VARIADIC_AT_HPP |