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 decltype(auto) operator[](difference_type n) const
12 // requires random_access_range<Base>
13
14 #include <cassert>
15 #include <ranges>
16 #include <tuple>
17
18 #include "test_iterators.h"
19
20 template <class T, class U>
21 concept CanSubscript = requires(T t, U u) { t[u]; };
22
23 template <class BaseRange>
24 using ElemIter = std::ranges::iterator_t<std::ranges::elements_view<BaseRange, 0>>;
25
26 using RandomAccessRange = std::ranges::subrange<std::tuple<int>*>;
27 static_assert(std::ranges::random_access_range<RandomAccessRange>);
28
29 static_assert(CanSubscript<ElemIter<RandomAccessRange>, int>);
30
31 using BidiRange = std::ranges::subrange<bidirectional_iterator<std::tuple<int>*>>;
32 static_assert(!std::ranges::random_access_range<BidiRange>);
33
34 static_assert(!CanSubscript<ElemIter<BidiRange>, int>);
35
test()36 constexpr bool test() {
37 {
38 // reference
39 std::tuple<int> ts[] = {{1}, {2}, {3}, {4}};
40 auto ev = ts | std::views::elements<0>;
41 auto it = ev.begin();
42
43 assert(&it[0] == &*it);
44 assert(&it[2] == &*(it + 2));
45
46 static_assert(std::is_same_v<decltype(it[2]), int&>);
47 }
48
49 {
50 // value
51 auto ev = std::views::iota(0, 5) | std::views::transform([](int i) { return std::tuple<int>{i}; }) |
52 std::views::elements<0>;
53 auto it = ev.begin();
54 assert(it[0] == *it);
55 assert(it[2] == *(it + 2));
56 assert(it[4] == *(it + 4));
57
58 static_assert(std::is_same_v<decltype(it[2]), int>);
59 }
60
61 return true;
62 }
63
main(int,char **)64 int main(int, char**) {
65 test();
66 static_assert(test());
67
68 return 0;
69 }
70