ceph/src/boost/libs/optional/include/boost/none_t.hpp

   1 // Copyright (C) 2003, Fernando Luis Cacciola Carballal.
   2 // Copyright (C) 2014, 2015 Andrzej Krzemienski.
   3 //
   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)
   7 //
   8 // See http://www.boost.org/libs/optional for documentation.
   9 //
  10 // You are welcome to contact the author at:
  11 //  fernando_cacciola@hotmail.com
  12 //
  13 #ifndef BOOST_NONE_T_17SEP2003_HPP
  14 #define BOOST_NONE_T_17SEP2003_HPP
  15
  16 namespace boost {
  17
  18 #ifdef BOOST_OPTIONAL_USE_OLD_DEFINITION_OF_NONE
  19
  20 namespace detail { struct none_helper{}; }
  21 typedef int detail::none_helper::*none_t ;
  22
  23 #elif defined BOOST_OPTIONAL_USE_SINGLETON_DEFINITION_OF_NONE
  24
  25 class none_t {};
  26
  27 #else
  28
  29 struct none_t
  30 {
  31   struct init_tag{};
  32   explicit none_t(init_tag){} // to disable default constructor
  33 };
  34
  35 #endif // old implementation workarounds
  36
  37 } // namespace boost
  38
  39 #endif // header guard