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1 | // |
2 | // cpp03/can_prefer_not_preferable_member_prefer.cpp | |
3 | // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2003-2020 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 | static const bool is_preferable = false; | |
18 | }; | |
19 | ||
20 | template <int> | |
21 | struct object | |
22 | { | |
23 | template <int N> | |
24 | object<N> prefer(prop<N>) const | |
25 | { | |
26 | return object<N>(); | |
27 | } | |
28 | }; | |
29 | ||
30 | namespace boost { | |
31 | namespace asio { | |
32 | ||
33 | template<int N, int M> | |
34 | struct is_applicable_property<object<N>, prop<M> > | |
35 | { | |
36 | static const bool value = true; | |
37 | }; | |
38 | ||
39 | namespace traits { | |
40 | ||
41 | template<int N, int M> | |
42 | struct prefer_member<object<N>, prop<M> > | |
43 | { | |
44 | static const bool is_valid = true; | |
45 | static const bool is_noexcept = true; | |
46 | typedef object<M> result_type; | |
47 | }; | |
48 | ||
49 | } // namespace traits | |
50 | } // namespace asio | |
51 | } // namespace boost | |
52 | ||
53 | int main() | |
54 | { | |
55 | assert((!boost::asio::can_prefer<object<1>, prop<2> >::value)); | |
56 | assert((!boost::asio::can_prefer<object<1>, prop<2>, prop<3> >::value)); | |
57 | assert((!boost::asio::can_prefer<object<1>, prop<2>, prop<3>, prop<4> >::value)); | |
58 | assert((!boost::asio::can_prefer<const object<1>, prop<2> >::value)); | |
59 | assert((!boost::asio::can_prefer<const object<1>, prop<2>, prop<3> >::value)); | |
60 | assert((!boost::asio::can_prefer<const object<1>, prop<2>, prop<3>, prop<4> >::value)); | |
61 | } |