1 // Copyright Daniel Wallin, David Abrahams 2010.
2 // Distributed under the Boost Software License, Version 1.0.
3 // (See accompanying file LICENSE_1_0.txt or copy at
4 // http://www.boost.org/LICENSE_1_0.txt)
5 
6 #ifndef BOOST_PARAMETER_IS_MAYBE_050329_HPP
7 #define BOOST_PARAMETER_IS_MAYBE_050329_HPP
8 
9 namespace boost { namespace parameter { namespace aux {
10 
11     struct maybe_base
12     {
13     };
14 }}} // namespace boost::parameter::aux
15 
16 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
17 #include <type_traits>
18 
19 namespace boost { namespace parameter { namespace aux {
20 
21     template <typename T>
22     using is_maybe = ::std::is_base_of<
23         ::boost::parameter::aux::maybe_base
24       , typename ::std::remove_const<T>::type
25     >;
26 }}} // namespace boost::parameter::aux
27 
28 #else   // !defined(BOOST_PARAMETER_CAN_USE_MP11)
29 #include <boost/mpl/bool.hpp>
30 #include <boost/mpl/if.hpp>
31 #include <boost/type_traits/is_base_of.hpp>
32 #include <boost/type_traits/remove_const.hpp>
33 
34 namespace boost { namespace parameter { namespace aux {
35 
36     template <typename T>
37     struct is_maybe
38       : ::boost::mpl::if_<
39             ::boost::is_base_of<
40                 ::boost::parameter::aux::maybe_base
41               , typename ::boost::remove_const<T>::type
42             >
43           , ::boost::mpl::true_
44           , ::boost::mpl::false_
45         >::type
46     {
47     };
48 }}} // namespace boost::parameter::aux
49 
50 #endif  // BOOST_PARAMETER_CAN_USE_MP11
51 #endif  // include guard
52 
53