| // Copyright (C) 2003, Fernando Luis Cacciola Carballal. |
| // Copyright (C) 2014, 2015 Andrzej Krzemienski. |
| // |
| // Use, modification, and distribution is subject to the Boost Software |
| // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| // http://www.boost.org/LICENSE_1_0.txt) |
| // |
| // See http://www.boost.org/libs/optional for documentation. |
| // |
| // You are welcome to contact the author at: |
| // fernando_cacciola@hotmail.com |
| // |
| #ifndef BOOST_NONE_T_17SEP2003_HPP |
| #define BOOST_NONE_T_17SEP2003_HPP |
| |
| #include <boost/config.hpp> |
| |
| namespace boost { |
| |
| #ifdef BOOST_OPTIONAL_USE_OLD_DEFINITION_OF_NONE |
| |
| namespace detail { struct none_helper{}; } |
| typedef int detail::none_helper::*none_t ; |
| |
| #elif defined BOOST_OPTIONAL_USE_SINGLETON_DEFINITION_OF_NONE |
| |
| class none_t {}; |
| |
| #else |
| |
| struct none_t |
| { |
| struct init_tag{}; |
| explicit BOOST_CONSTEXPR none_t(init_tag){} // to disable default constructor |
| }; |
| |
| #endif // old implementation workarounds |
| |
| } // namespace boost |
| |
| #endif // header guard |
