1 // Copyright (C) 2003, Fernando Luis Cacciola Carballal.
2 // Copyright (C) 2014 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
18 #ifdef BOOST_OPTIONAL_USE_OLD_DEFINITION_OF_NONE
20 namespace detail { struct none_helper{}; }
21 typedef int detail::none_helper::*none_t ;
23 #elif defined BOOST_OPTIONAL_USE_SINGLETON_DEFINITION_OF_NONE
32 explicit none_t(init_tag){} // to prevent default constructor
35 #endif // old implementation workarounds
39 #endif // header guard