projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | /*! |
| 2 | @file | |
| 3 | Forward declares `boost::hana::one`. | |
| 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_FWD_ONE_HPP | |
| 11 | #define BOOST_HANA_FWD_ONE_HPP | |
| 12 | ||
| 13 | #include <boost/hana/config.hpp> | |
| 14 | #include <boost/hana/core/when.hpp> | |
| 15 | ||
| 16 | ||
| 17 | BOOST_HANA_NAMESPACE_BEGIN | |
| 18 | //! Identity of the `Ring` multiplication. | |
| 19 | //! @ingroup group-Ring | |
| 20 | //! | |
| 21 | //! @tparam R | |
| 22 | //! The tag (must be a model of `Ring`) of the returned identity. | |
| 23 | //! | |
| 24 | //! | |
| 25 | //! Example | |
| 26 | //! ------- | |
| 27 | //! @include example/one.cpp | |
| 28 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
| 29 | template <typename R> | |
| 30 | constexpr auto one = []() -> decltype(auto) { | |
| 31 | return tag-dispatched; | |
| 32 | }; | |
| 33 | #else | |
| 34 | template <typename R, typename = void> | |
| 35 | struct one_impl : one_impl<R, when<true>> { }; | |
| 36 | ||
| 37 | template <typename R> | |
| 38 | struct one_t; | |
| 39 | ||
| 40 | template <typename R> | |
| 41 | constexpr one_t<R> one{}; | |
| 42 | #endif | |
| 43 | BOOST_HANA_NAMESPACE_END | |
| 44 | ||
| 45 | #endif // !BOOST_HANA_FWD_ONE_HPP |