| // Copyright (C) 2003, Fernando Luis Cacciola Carballal. |
| // Copyright (C) 2014 Andrzej Krzemienski. |
| // |
| // Distributed under 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_17SEP2003_HPP |
| #define BOOST_NONE_17SEP2003_HPP |
| |
| #include "boost/none_t.hpp" |
| |
| // NOTE: Borland users have to include this header outside any precompiled headers |
| // (bcc<=5.64 cannot include instance data in a precompiled header) |
| // -- * To be verified, now that there's no unnamed namespace |
| |
| namespace boost { |
| |
| #ifdef BOOST_OPTIONAL_USE_OLD_DEFINITION_OF_NONE |
| none_t const none = (static_cast<none_t>(0)) ; |
| #else |
| |
| namespace detail { namespace optional_detail { |
| |
| // the trick here is to make boost::none defined once as a global but in a header file |
| template <typename T> |
| struct none_instance |
| { |
| static const T instance; |
| }; |
| |
| template <typename T> |
| const T none_instance<T>::instance = T(); // global, but because 'tis a template, no cpp file required |
| |
| } } // namespace detail::optional_detail |
| |
| |
| namespace { |
| // TU-local |
| const none_t& none = detail::optional_detail::none_instance<none_t>::instance; |
| } |
| |
| #endif |
| |
| } // namespace boost |
| |
| #endif |
| |