1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9// UNSUPPORTED: c++03, c++11, c++14, c++17
10
11// constexpr iterator& operator--() requires bidirectional_range<Base>;
12// constexpr iterator operator--(int) requires bidirectional_range<Base>;
13
14#include <array>
15#include <cassert>
16#include <ranges>
17#include <tuple>
18
19#include "test_iterators.h"
20
21template <class Iter>
22concept CanPreDecrement = requires(Iter it) { --it; };
23
24template <class Iter>
25concept CanPostDecrement = requires(Iter it) { it--; };
26
27template <class Iter, class Sent = sentinel_wrapper<Iter>>
28constexpr void testOne() {
29 using Range = std::ranges::subrange<Iter, Sent>;
30 std::tuple<int> ts[] = {{1}, {2}, {3}};
31 auto ev = Range{Iter{&ts[0]}, Sent{Iter{&ts[0] + 3}}} | std::views::elements<0>;
32
33 using ElementIter = std::ranges::iterator_t<decltype(ev)>;
34
35 if constexpr (!std::bidirectional_iterator<Iter>) {
36 auto it = ev.begin();
37 static_assert(!CanPreDecrement<decltype(it)>);
38 static_assert(!CanPostDecrement<decltype(it)>);
39 } else {
40 // --i
41 {
42 auto it = ev.begin();
43 static_assert(CanPreDecrement<decltype(it)>);
44
45 ++it;
46 assert(base(it.base()) == &ts[1]);
47
48 decltype(auto) result = --it;
49
50 static_assert(std::is_same_v<decltype(result), ElementIter&>);
51 assert(&result == &it);
52
53 assert(base(it.base()) == &ts[0]);
54 }
55
56 // i--
57 {
58 auto it = ev.begin();
59 static_assert(CanPostDecrement<decltype(it)>);
60
61 ++it;
62 assert(base(it.base()) == &ts[1]);
63
64 decltype(auto) result = it--;
65
66 static_assert(std::is_same_v<decltype(result), ElementIter>);
67
68 assert(base(it.base()) == &ts[0]);
69 assert(base(result.base()) == &ts[1]);
70 }
71 }
72}
73
74constexpr bool test() {
75 using Ptr = std::tuple<int>*;
76 testOne<cpp20_input_iterator<Ptr>>();
77 testOne<forward_iterator<Ptr>>();
78 testOne<bidirectional_iterator<Ptr>>();
79 testOne<random_access_iterator<Ptr>>();
80 testOne<contiguous_iterator<Ptr>>();
81 testOne<Ptr>();
82
83 return true;
84}
85
86int main(int, char**) {
87 test();
88 static_assert(test());
89
90 return 0;
91}
92

source code of libcxx/test/std/ranges/range.adaptors/range.elements/iterator/decrement.pass.cpp