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, c++20
10 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
11 
12 // template <bool OtherConst>
13 // requires(sized_sentinel_for<sentinel_t<maybe-const<Const, Views>>,
14 //                             iterator_t<maybe-const<OtherConst, Views>>>&&...)
15 // friend constexpr common_type_t<range_difference_t<maybe-const<OtherConst, Views>>...>
16 // 	operator-(const iterator<OtherConst>&, const sentinel&)
17 //
18 // template <bool OtherConst>
19 // requires(sized_sentinel_for<sentinel_t<maybe-const<Const, Views>>,
20 //                             iterator_t<maybe-const<OtherConst, Views>>>&&...)
21 // friend constexpr common_type_t<range_difference_t<maybe-const<OtherConst, Views>>...>
22 //   operator-(const sentinel&, const iterator<OtherConst>&)
23 
24 #include <cassert>
25 #include <concepts>
26 #include <functional>
27 #include <ranges>
28 #include <tuple>
29 
30 #include "../types.h"
31 
32 template <class Base = int*>
33 struct convertible_forward_sized_iterator {
34   Base it_ = nullptr;
35 
36   using iterator_category = std::forward_iterator_tag;
37   using value_type = int;
38   using difference_type = intptr_t;
39 
40   convertible_forward_sized_iterator() = default;
41   constexpr convertible_forward_sized_iterator(Base it) : it_(it) {}
42 
43   template <std::convertible_to<Base> U>
44   constexpr convertible_forward_sized_iterator(const convertible_forward_sized_iterator<U>& it) : it_(it.it_) {}
45 
46   constexpr decltype(*Base{}) operator*() const { return *it_; }
47 
48   constexpr convertible_forward_sized_iterator& operator++() {
49     ++it_;
50     return *this;
51   }
52   constexpr convertible_forward_sized_iterator operator++(int) { return forward_sized_iterator(it_++); }
53 
54   friend constexpr bool operator==(const convertible_forward_sized_iterator&,
55                                    const convertible_forward_sized_iterator&) = default;
56 
57   friend constexpr difference_type operator-(const convertible_forward_sized_iterator& x,
58                                              const convertible_forward_sized_iterator& y) {
59     return x.it_ - y.it_;
60   }
61 };
62 static_assert(std::forward_iterator<convertible_forward_sized_iterator<>>);
63 
64 template <class Base>
65 struct convertible_sized_sentinel {
66   Base base_;
67   explicit convertible_sized_sentinel() = default;
68   constexpr convertible_sized_sentinel(const Base& it) : base_(it) {}
69 
70   template <std::convertible_to<Base> U>
71   constexpr convertible_sized_sentinel(const convertible_sized_sentinel<U>& other) : base_(other.base_) {}
72 
73   template <class U>
74     requires(std::convertible_to<Base, U> || std::convertible_to<U, Base>)
75   friend constexpr bool operator==(const convertible_sized_sentinel& s, const U& base) {
76     return s.base_ == base;
77   }
78   template <class U>
79     requires(std::convertible_to<Base, U> || std::convertible_to<U, Base>)
80   friend constexpr auto operator-(const convertible_sized_sentinel& s, const U& i) {
81     return s.base_ - i;
82   }
83 
84   template <class U>
85     requires(std::convertible_to<Base, U> || std::convertible_to<U, Base>)
86   friend constexpr auto operator-(const U& i, const convertible_sized_sentinel& s) {
87     return i - s.base_;
88   }
89 };
90 static_assert(std::sized_sentinel_for<convertible_sized_sentinel<convertible_forward_sized_iterator<>>,
91                                       convertible_forward_sized_iterator<>>);
92 static_assert(std::sized_sentinel_for<convertible_sized_sentinel<convertible_forward_sized_iterator<const int*>>,
93                                       convertible_forward_sized_iterator<int*>>);
94 static_assert(std::sized_sentinel_for<convertible_sized_sentinel<convertible_forward_sized_iterator<int*>>,
95                                       convertible_forward_sized_iterator<const int*>>);
96 
97 struct ConstCompatibleForwardSized : IntBufferView {
98   using IntBufferView::IntBufferView;
99 
100   using iterator = convertible_forward_sized_iterator<int*>;
101   using const_iterator = convertible_forward_sized_iterator<const int*>;
102 
103   constexpr iterator begin() { return {buffer_}; }
104   constexpr const_iterator begin() const { return {buffer_}; }
105   constexpr convertible_sized_sentinel<iterator> end() { return iterator{buffer_ + size_}; }
106   constexpr convertible_sized_sentinel<const_iterator> end() const { return const_iterator{buffer_ + size_}; }
107 };
108 
109 // clang-format off
110 template <class T, class U>
111 concept HasMinus = std::invocable<std::minus<>,const T&, const U&>;
112 
113 template <class T>
114 concept SentinelHasMinus = HasMinus<std::ranges::sentinel_t<T>, std::ranges::iterator_t<T>>;
115 // clang-format on
116 
117 constexpr bool test() {
118   int buffer1[5] = {1, 2, 3, 4, 5};
119 
120   {
121     // simple-view
122     std::ranges::zip_view v{ForwardSizedNonCommon(buffer1)};
123     static_assert(!std::ranges::common_range<decltype(v)>);
124     LIBCPP_STATIC_ASSERT(std::ranges::__simple_view<decltype(v)>);
125 
126     auto it = v.begin();
127     auto st = v.end();
128     assert(st - it == 5);
129     assert(st - std::ranges::next(it, 1) == 4);
130 
131     assert(it - st == -5);
132     assert(std::ranges::next(it, 1) - st == -4);
133     static_assert(SentinelHasMinus<decltype(v)>);
134   }
135 
136   {
137     // shortest range
138     std::ranges::zip_view v(std::views::iota(0, 3), ForwardSizedNonCommon(buffer1));
139     static_assert(!std::ranges::common_range<decltype(v)>);
140     auto it = v.begin();
141     auto st = v.end();
142     assert(st - it == 3);
143     assert(st - std::ranges::next(it, 1) == 2);
144 
145     assert(it - st == -3);
146     assert(std::ranges::next(it, 1) - st == -2);
147     static_assert(SentinelHasMinus<decltype(v)>);
148   }
149 
150   {
151     // underlying sentinel does not model sized_sentinel_for
152     std::ranges::zip_view v(std::views::iota(0), SizedRandomAccessView(buffer1));
153     static_assert(!std::ranges::common_range<decltype(v)>);
154     static_assert(!SentinelHasMinus<decltype(v)>);
155   }
156 
157   {
158     // const imcompatible:
159     // underlying const sentinels cannot substract underlying iterators
160     // underlying sentinels cannot substract underlying const iterators
161     std::ranges::zip_view v(NonSimpleForwardSizedNonCommon{buffer1});
162     static_assert(!std::ranges::common_range<decltype(v)>);
163     LIBCPP_STATIC_ASSERT(!std::ranges::__simple_view<decltype(v)>);
164 
165     using Iter = std::ranges::iterator_t<decltype(v)>;
166     using ConstIter = std::ranges::iterator_t<const decltype(v)>;
167     static_assert(!std::is_same_v<Iter, ConstIter>);
168     using Sentinel = std::ranges::sentinel_t<decltype(v)>;
169     using ConstSentinel = std::ranges::sentinel_t<const decltype(v)>;
170     static_assert(!std::is_same_v<Sentinel, ConstSentinel>);
171 
172     static_assert(HasMinus<Iter, Sentinel>);
173     static_assert(HasMinus<Sentinel, Iter>);
174     static_assert(HasMinus<ConstIter, ConstSentinel>);
175     static_assert(HasMinus<ConstSentinel, ConstIter>);
176     auto it = v.begin();
177     auto const_it = std::as_const(v).begin();
178     auto st = v.end();
179     auto const_st = std::as_const(v).end();
180     assert(it - st == -5);
181     assert(st - it == 5);
182     assert(const_it - const_st == -5);
183     assert(const_st - const_it == 5);
184 
185     static_assert(!HasMinus<Iter, ConstSentinel>);
186     static_assert(!HasMinus<ConstSentinel, Iter>);
187     static_assert(!HasMinus<ConstIter, Sentinel>);
188     static_assert(!HasMinus<Sentinel, ConstIter>);
189   }
190 
191   {
192     // const compatible allow non-const to const conversion
193     std::ranges::zip_view v(ConstCompatibleForwardSized{buffer1});
194     static_assert(!std::ranges::common_range<decltype(v)>);
195     LIBCPP_STATIC_ASSERT(!std::ranges::__simple_view<decltype(v)>);
196 
197     using Iter = std::ranges::iterator_t<decltype(v)>;
198     using ConstIter = std::ranges::iterator_t<const decltype(v)>;
199     static_assert(!std::is_same_v<Iter, ConstIter>);
200     using Sentinel = std::ranges::sentinel_t<decltype(v)>;
201     using ConstSentinel = std::ranges::sentinel_t<const decltype(v)>;
202     static_assert(!std::is_same_v<Sentinel, ConstSentinel>);
203 
204     static_assert(HasMinus<Iter, Sentinel>);
205     static_assert(HasMinus<Sentinel, Iter>);
206     static_assert(HasMinus<ConstIter, ConstSentinel>);
207     static_assert(HasMinus<ConstSentinel, ConstIter>);
208     static_assert(HasMinus<Iter, ConstSentinel>);
209     static_assert(HasMinus<ConstSentinel, Iter>);
210     static_assert(HasMinus<ConstIter, Sentinel>);
211     static_assert(HasMinus<Sentinel, ConstIter>);
212 
213     auto it = v.begin();
214     auto const_it = std::as_const(v).begin();
215     auto st = v.end();
216     auto const_st = std::as_const(v).end();
217 
218     assert(it - st == -5);
219     assert(st - it == 5);
220     assert(const_it - const_st == -5);
221     assert(const_st - const_it == 5);
222     assert(it - const_st == -5);
223     assert(const_st - it == 5);
224     assert(const_it - st == -5);
225     assert(st - const_it == 5);
226   }
227   return true;
228 }
229 
230 int main(int, char**) {
231   test();
232   static_assert(test());
233 
234   return 0;
235 }
236