1// Copyright Louis Dionne 2013-2022
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/at.hpp>
6#include <boost/hana/at_key.hpp>
7#include <boost/hana/back.hpp>
8#include <boost/hana/ext/std/tuple.hpp>
9#include <boost/hana/front.hpp>
10#include <boost/hana/integral_constant.hpp>
11
12#include <tuple>
13#include <utility>
14namespace hana = boost::hana;
15
16
17template <typename T>
18T const& cref(T& t) { return t; }
19
20// a non-movable, non-copyable type
21struct RefOnly {
22 RefOnly() = default;
23 RefOnly(RefOnly const&) = delete;
24 RefOnly(RefOnly&&) = delete;
25};
26
27template <int i>
28struct RefOnly_i : hana::int_<i> {
29 RefOnly_i() = default;
30 RefOnly_i(RefOnly_i const&) = delete;
31 RefOnly_i(RefOnly_i&&) = delete;
32};
33
34int main() {
35 std::tuple<RefOnly> t;
36
37 // Make sure that we return the proper reference types from `at`.
38 {
39 RefOnly&& r1 = hana::at_c<0>(xs: std::move(t));
40 RefOnly& r2 = hana::at_c<0>(xs&: t);
41 RefOnly const& r3 = hana::at_c<0>(xs: cref(t));
42
43 (void)r1; (void)r2; (void)r3;
44 }
45
46 // Make sure we return the proper reference types from `front`.
47 {
48 RefOnly&& r1 = hana::front(std::move(t));
49 RefOnly& r2 = hana::front(t);
50 RefOnly const& r3 = hana::front(cref(t));
51
52 (void)r1; (void)r2; (void)r3;
53 }
54
55 // Make sure we return the proper reference types from `back`.
56 {
57 RefOnly&& r1 = hana::back(std::move(t));
58 RefOnly& r2 = hana::back(t);
59 RefOnly const& r3 = hana::back(cref(t));
60
61 (void)r1; (void)r2; (void)r3;
62 }
63
64 // Make sure we return the proper reference types from `at_key`.
65 {
66 std::tuple<RefOnly_i<3>> t{};
67 RefOnly_i<3>& r1 = hana::at_key(t, RefOnly_i<3>{});
68 RefOnly_i<3> const& r2 = hana::at_key(cref(t), RefOnly_i<3>{});
69 RefOnly_i<3>&& r3 = hana::at_key(std::move(t), RefOnly_i<3>{});
70
71 (void)r1; (void)r2; (void)r3;
72 }
73}
74

source code of boost/libs/hana/test/ext/std/tuple/issue_90.cpp