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1 | // Copyright Louis Dionne 2013-2016 |
2 | // Distributed under the Boost Software License, Version 1.0. | |
3 | // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) | |
4 | ||
5 | #include <boost/hana/assert.hpp> | |
6 | #include <boost/hana/first.hpp> | |
7 | #include <boost/hana/pair.hpp> | |
8 | #include <boost/hana/second.hpp> | |
9 | ||
10 | #include <utility> | |
11 | namespace hana = boost::hana; | |
12 | ||
13 | ||
14 | struct MoveOnly { | |
15 | int data_; | |
16 | MoveOnly(MoveOnly const&) = delete; | |
17 | MoveOnly& operator=(MoveOnly const&) = delete; | |
18 | MoveOnly(int data = 1) : data_(data) { } | |
19 | MoveOnly(MoveOnly&& x) : data_(x.data_) { x.data_ = 0; } | |
20 | ||
21 | MoveOnly& operator=(MoveOnly&& x) | |
22 | { data_ = x.data_; x.data_ = 0; return *this; } | |
23 | ||
24 | bool operator==(const MoveOnly& x) const { return data_ == x.data_; } | |
25 | }; | |
26 | ||
27 | struct MoveOnlyDerived : MoveOnly { | |
28 | MoveOnlyDerived(MoveOnlyDerived&&) = default; | |
29 | MoveOnlyDerived(int data = 1) : MoveOnly(data) { } | |
30 | }; | |
31 | ||
32 | constexpr auto in_constexpr_context(int a, short b) { | |
33 | hana::pair<int, short> p1(a, b); | |
34 | hana::pair<int, short> p2; | |
35 | hana::pair<double, long> p3; | |
36 | p2 = std::move(p1); | |
37 | p3 = std::move(p2); | |
38 | return p3; | |
39 | } | |
40 | ||
41 | int main() { | |
42 | // from pair<T, U> to pair<T, U> | |
43 | { | |
44 | hana::pair<MoveOnly, short> p1(MoveOnly{3}, 4); | |
45 | hana::pair<MoveOnly, short> p2; | |
46 | p2 = std::move(p1); | |
47 | BOOST_HANA_RUNTIME_CHECK(hana::first(p2) == MoveOnly{3}); | |
48 | BOOST_HANA_RUNTIME_CHECK(hana::second(p2) == 4); | |
49 | } | |
50 | ||
51 | // from pair<T, U> to pair<V, W> | |
52 | { | |
53 | hana::pair<MoveOnlyDerived, short> p1(MoveOnlyDerived{3}, 4); | |
54 | hana::pair<MoveOnly, long> p2; | |
55 | p2 = std::move(p1); | |
56 | BOOST_HANA_RUNTIME_CHECK(hana::first(p2) == MoveOnly{3}); | |
57 | BOOST_HANA_RUNTIME_CHECK(hana::second(p2) == 4); | |
58 | } | |
59 | ||
60 | // make sure that also works in a constexpr context | |
61 | { | |
62 | constexpr auto p = in_constexpr_context(3, 4); | |
63 | static_assert(hana::first(p) == 3, ""); | |
64 | static_assert(hana::second(p) == 4, ""); | |
65 | } | |
66 | } |