| // |
| // cpp11/require_free.cpp |
| // ~~~~~~~~~~~~~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2021 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 <boost/asio/require.hpp> |
| #include <cassert> |
| |
| template <int> |
| struct prop |
| { |
| static constexpr bool is_requirable = true; |
| }; |
| |
| template <int> |
| struct object |
| { |
| template <int N> |
| friend constexpr object<N> require(const object&, prop<N>) |
| { |
| return object<N>(); |
| } |
| }; |
| |
| namespace boost { |
| namespace asio { |
| |
| template<int N, int M> |
| struct is_applicable_property<object<N>, prop<M> > |
| { |
| static constexpr bool value = true; |
| }; |
| |
| } // namespace asio |
| } // namespace boost |
| |
| int main() |
| { |
| object<1> o1 = {}; |
| object<2> o2 = boost::asio::require(o1, prop<2>()); |
| object<3> o3 = boost::asio::require(o1, prop<2>(), prop<3>()); |
| object<4> o4 = boost::asio::require(o1, prop<2>(), prop<3>(), prop<4>()); |
| (void)o2; |
| (void)o3; |
| (void)o4; |
| |
| const object<1> o5 = {}; |
| object<2> o6 = boost::asio::require(o5, prop<2>()); |
| object<3> o7 = boost::asio::require(o5, prop<2>(), prop<3>()); |
| object<4> o8 = boost::asio::require(o5, prop<2>(), prop<3>(), prop<4>()); |
| (void)o6; |
| (void)o7; |
| (void)o8; |
| |
| constexpr object<2> o9 = boost::asio::require(object<1>(), prop<2>()); |
| constexpr object<3> o10 = boost::asio::require(object<1>(), prop<2>(), prop<3>()); |
| constexpr object<4> o11 = boost::asio::require(object<1>(), prop<2>(), prop<3>(), prop<4>()); |
| (void)o9; |
| (void)o10; |
| (void)o11; |
| } |