Chris@16: // Copyright (C) 2003, Fernando Luis Cacciola Carballal.
Chris@101: // Copyright (C) 2014 Andrzej Krzemienski.
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0.
Chris@16: // (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // See http://www.boost.org/libs/optional for documentation.
Chris@16: //
Chris@16: // You are welcome to contact the author at:
Chris@16: //  fernando_cacciola@hotmail.com
Chris@16: //
Chris@16: #ifndef BOOST_NONE_17SEP2003_HPP
Chris@16: #define BOOST_NONE_17SEP2003_HPP
Chris@16: 
Chris@16: #include "boost/none_t.hpp"
Chris@16: 
Chris@16: // NOTE: Borland users have to include this header outside any precompiled headers
Chris@16: // (bcc<=5.64 cannot include instance data in a precompiled header)
Chris@16: //  -- * To be verified, now that there's no unnamed namespace
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@101: #ifdef BOOST_OPTIONAL_USE_OLD_DEFINITION_OF_NONE
Chris@16: none_t const none = (static_cast<none_t>(0)) ;
Chris@101: #else
Chris@101: 
Chris@101: namespace detail { namespace optional_detail {
Chris@101: 
Chris@101:   // the trick here is to make boost::none defined once as a global but in a header file
Chris@101:   template <typename T>
Chris@101:   struct none_instance
Chris@101:   {
Chris@101:     static const T instance;
Chris@101:   };
Chris@101:   
Chris@101:   template <typename T>
Chris@101:   const T none_instance<T>::instance = T(); // global, but because 'tis a template, no cpp file required
Chris@101: 
Chris@101: } } // namespace detail::optional_detail
Chris@101: 
Chris@101: 
Chris@101: namespace {
Chris@101:   // TU-local
Chris@101:   const none_t& none = detail::optional_detail::none_instance<none_t>::instance; 
Chris@101: }
Chris@101: 
Chris@101: #endif
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif
Chris@16: