// // cpp11/require_concept_free.cpp // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // // Copyright (c) 2003-2024 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/require_concept.hpp" #include template struct prop { static constexpr bool is_requirable_concept = true; }; template struct object { template friend constexpr object require_concept(const object&, prop) { return object(); } }; namespace asio { template struct is_applicable_property, prop > { static constexpr bool value = true; }; } // namespace asio int main() { object<1> o1 = {}; object<2> o2 = asio::require_concept(o1, prop<2>()); (void)o2; const object<1> o3 = {}; object<2> o4 = asio::require_concept(o3, prop<2>()); (void)o4; constexpr object<2> o5 = asio::require_concept(object<1>(), prop<2>()); (void)o5; }