1 //
2 // cpp14/can_prefer_member_require.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 template <typename> static constexpr bool is_applicable_property_v = true;
18 static constexpr bool is_preferable = true;
19 };
20
21 template <int>
22 struct object
23 {
24 template <int N>
requireobject25 constexpr object<N> require(prop<N>) const
26 {
27 return object<N>();
28 }
29 };
30
main()31 int main()
32 {
33 static_assert(boost::asio::can_prefer_v<object<1>, prop<2>>, "");
34 static_assert(boost::asio::can_prefer_v<object<1>, prop<2>, prop<3>>, "");
35 static_assert(boost::asio::can_prefer_v<object<1>, prop<2>, prop<3>, prop<4>>, "");
36 static_assert(boost::asio::can_prefer_v<const object<1>, prop<2>>, "");
37 static_assert(boost::asio::can_prefer_v<const object<1>, prop<2>, prop<3>>, "");
38 static_assert(boost::asio::can_prefer_v<const object<1>, prop<2>, prop<3>, prop<4>>, "");
39 }
40