1 //
2 // cpp11/can_prefer_member_prefer.cpp
3 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4 //
5 // Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com)
6 //
7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
9 //
10
11 #include <boost/asio/prefer.hpp>
12 #include <cassert>
13
14 template <int>
15 struct prop
16 {
17 static constexpr bool is_preferable = true;
18 };
19
20 template <int>
21 struct object
22 {
23 template <int N>
preferobject24 constexpr object<N> prefer(prop<N>) const
25 {
26 return object<N>();
27 }
28 };
29
30 namespace boost {
31 namespace asio {
32
33 template<int N, int M>
34 struct is_applicable_property<object<N>, prop<M> >
35 {
36 static constexpr bool value = true;
37 };
38
39 } // namespace asio
40 } // namespace boost
41
main()42 int main()
43 {
44 static_assert(boost::asio::can_prefer<object<1>, prop<2>>::value, "");
45 static_assert(boost::asio::can_prefer<object<1>, prop<2>, prop<3>>::value, "");
46 static_assert(boost::asio::can_prefer<object<1>, prop<2>, prop<3>, prop<4>>::value, "");
47 static_assert(boost::asio::can_prefer<const object<1>, prop<2>>::value, "");
48 static_assert(boost::asio::can_prefer<const object<1>, prop<2>, prop<3>>::value, "");
49 static_assert(boost::asio::can_prefer<const object<1>, prop<2>, prop<3>, prop<4>>::value, "");
50 }
51