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