// Copyright (C) 2003, Fernando Luis Cacciola Carballal.

// Copyright (C) 2014, 2015 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)) ;

#elif defined BOOST_OPTIONAL_USE_SINGLETON_DEFINITION_OF_NONE

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; 

}

#else

const none_t none ((none_t::init_tag()));

#endif // older definitions

} // namespace boost

#endif // header guard