ceph/src/boost/libs/variant/include/boost/variant/detail/has_result_type.hpp

   1 //-----------------------------------------------------------------------------
   2 // boost variant/detail/has_result_type.hpp header file
   3 // See http://www.boost.org for updates, documentation, and revision history.
   4 //-----------------------------------------------------------------------------
   5 //
   6 // Copyright (c) 2014-2015 Antony Polukhin
   7 //
   8 // Distributed under the Boost Software License, Version 1.0. (See
   9 // accompanying file LICENSE_1_0.txt or copy at
  10 // http://www.boost.org/LICENSE_1_0.txt)
  11
  12 #ifndef BOOST_VARIANT_DETAIL_HAS_RESULT_TYPE_HPP
  13 #define BOOST_VARIANT_DETAIL_HAS_RESULT_TYPE_HPP
  14
  15 #include <boost/config.hpp>
  16 #include <boost/type_traits/remove_reference.hpp>
  17
  18
  19 namespace boost { namespace detail { namespace variant {
  20
  21 template <typename T >
  22 struct has_result_type {
  23 private:
  24     typedef char                      yes;
  25     typedef struct { char array[2]; } no;
  26
  27     template<typename C> static yes test(typename boost::remove_reference<typename C::result_type>::type*);
  28     template<typename C> static no  test(...);
  29
  30 public:
  31     BOOST_STATIC_CONSTANT(bool, value = sizeof(test<T>(0)) == sizeof(yes));
  32 };
  33
  34 }}} // namespace boost::detail::variant
  35
  36 #endif // BOOST_VARIANT_DETAIL_HAS_RESULT_TYPE_HPP
  37