// // cpp14/can_prefer_free_prefer.cpp // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // // Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com) // // Distributed under the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // #include "asio/prefer.hpp" #include <cassert> template <int> struct prop { template <typename> static constexpr bool is_applicable_property_v = true; static constexpr bool is_preferable = true; }; template <int> struct object { template <int N> friend constexpr object<N> prefer(const object&, prop<N>) { return object<N>(); } }; int main() { static_assert(asio::can_prefer_v<object<1>, prop<2>>, ""); static_assert(asio::can_prefer_v<object<1>, prop<2>, prop<3>>, ""); static_assert(asio::can_prefer_v<object<1>, prop<2>, prop<3>, prop<4>>, ""); static_assert(asio::can_prefer_v<const object<1>, prop<2>>, ""); static_assert(asio::can_prefer_v<const object<1>, prop<2>, prop<3>>, ""); static_assert(asio::can_prefer_v<const object<1>, prop<2>, prop<3>, prop<4>>, ""); }