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1 | // |
2 | // cpp14/prefer_free_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 | template <typename> static constexpr bool is_applicable_property_v = true; | |
18 | static constexpr bool is_preferable = true; | |
19 | }; | |
20 | ||
21 | template <int> | |
22 | struct object | |
23 | { | |
24 | template <int N> | |
25 | friend constexpr object<N> prefer(const object&, prop<N>) | |
26 | { | |
27 | return object<N>(); | |
28 | } | |
29 | }; | |
30 | ||
31 | int main() | |
32 | { | |
33 | object<1> o1 = {}; | |
34 | object<2> o2 = boost::asio::prefer(o1, prop<2>()); | |
35 | object<3> o3 = boost::asio::prefer(o1, prop<2>(), prop<3>()); | |
36 | object<4> o4 = boost::asio::prefer(o1, prop<2>(), prop<3>(), prop<4>()); | |
37 | (void)o2; | |
38 | (void)o3; | |
39 | (void)o4; | |
40 | ||
41 | const object<1> o5 = {}; | |
42 | object<2> o6 = boost::asio::prefer(o5, prop<2>()); | |
43 | object<3> o7 = boost::asio::prefer(o5, prop<2>(), prop<3>()); | |
44 | object<4> o8 = boost::asio::prefer(o5, prop<2>(), prop<3>(), prop<4>()); | |
45 | (void)o6; | |
46 | (void)o7; | |
47 | (void)o8; | |
48 | ||
49 | constexpr object<2> o9 = boost::asio::prefer(object<1>(), prop<2>()); | |
50 | constexpr object<3> o10 = boost::asio::prefer(object<1>(), prop<2>(), prop<3>()); | |
51 | constexpr object<4> o11 = boost::asio::prefer(object<1>(), prop<2>(), prop<3>(), prop<4>()); | |
52 | (void)o9; | |
53 | (void)o10; | |
54 | (void)o11; | |
55 | } |