ceph/src/boost/libs/mp11/test/mp_defer.cpp

   1
   2 // Copyright 2015-2017 Peter Dimov.
   3 //
   4 // Distributed under the Boost Software License, Version 1.0.
   5 //
   6 // See accompanying file LICENSE_1_0.txt or copy at
   7 // http://www.boost.org/LICENSE_1_0.txt
   8
   9
  10 #include <boost/mp11/utility.hpp>
  11 #include <boost/mp11/integral.hpp>
  12 #include <boost/core/lightweight_test_trait.hpp>
  13 #include <type_traits>
  14
  15 using boost::mp11::mp_identity;
  16 using boost::mp11::mp_true;
  17 using boost::mp11::mp_false;
  18
  19 template<class T> struct has_type
  20 {
  21     template<class U> static mp_true f( mp_identity<typename U::type>* );
  22     template<class U> static mp_false f( ... );
  23
  24     using type = decltype( f<T>(0) );
  25
  26     static const bool value = type::value;
  27 };
  28
  29 using boost::mp11::mp_defer;
  30
  31 template<class T> using add_pointer = T*;
  32 template<class... T> using add_pointer_impl = mp_defer<add_pointer, T...>;
  33
  34 int main()
  35 {
  36     BOOST_TEST_TRAIT_TRUE((has_type<add_pointer_impl<void>>));
  37     BOOST_TEST_TRAIT_TRUE((std::is_same<add_pointer_impl<void>::type, void*>));
  38
  39     BOOST_TEST_TRAIT_TRUE((has_type<add_pointer_impl<int>>));
  40     BOOST_TEST_TRAIT_TRUE((std::is_same<add_pointer_impl<int>::type, int*>));
  41
  42     BOOST_TEST_TRAIT_FALSE((has_type<add_pointer_impl<>>));
  43     BOOST_TEST_TRAIT_FALSE((has_type<add_pointer_impl<void, void>>));
  44
  45     return boost::report_errors();
  46 }