1//
2// cpp03/can_prefer_not_applicable_free_require.cpp
3// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4//
5// Copyright (c) 2003-2024 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
14template <int>
15struct prop
16{
17 static const bool is_preferable = true;
18};
19
20template <int>
21struct object
22{
23 template <int N>
24 friend object<N> require(const object&, prop<N>)
25 {
26 return object<N>();
27 }
28};
29
30namespace boost {
31namespace asio {
32namespace traits {
33
34template<int N, int M>
35struct require_free<object<N>, prop<M> >
36{
37 static const bool is_valid = true;
38 static const bool is_noexcept = true;
39 typedef object<M> result_type;
40};
41
42} // namespace traits
43} // namespace asio
44} // namespace boost
45
46int main()
47{
48 assert((!boost::asio::can_prefer<object<1>, prop<2> >::value));
49 assert((!boost::asio::can_prefer<object<1>, prop<2>, prop<3> >::value));
50 assert((!boost::asio::can_prefer<object<1>, prop<2>, prop<3>, prop<4> >::value));
51 assert((!boost::asio::can_prefer<const object<1>, prop<2> >::value));
52 assert((!boost::asio::can_prefer<const object<1>, prop<2>, prop<3> >::value));
53 assert((!boost::asio::can_prefer<const object<1>, prop<2>, prop<3>, prop<4> >::value));
54}
55

source code of boost/libs/asio/test/properties/cpp03/can_prefer_not_applicable_free_require.cpp