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 // <algorithm>
10 
11 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
12 
13 // template<input_iterator I1, sentinel_for<I1> S1, input_iterator I2, sentinel_for<I2> S2,
14 //          class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
15 //   requires indirectly_comparable<I1, I2, Pred, Proj1, Proj2>
16 //   constexpr bool ranges::starts_with(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
17 //                                      Proj1 proj1 = {}, Proj2 proj2 = {});
18 // template<input_range R1, input_range R2, class Pred = ranges::equal_to, class Proj1 = identity,
19 //          class Proj2 = identity>
20 //   requires indirectly_comparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
21 //   constexpr bool ranges::starts_with(R1&& r1, R2&& r2, Pred pred = {},
22 //                                      Proj1 proj1 = {}, Proj2 proj2 = {});
23 
24 #include <algorithm>
25 #include <array>
26 #include <ranges>
27 
28 #include "almost_satisfies_types.h"
29 #include "test_iterators.h"
30 
31 template <class Iter1, class Sent1 = Iter1, class Iter2 = int*, class Sent2 = Iter2>
32 concept HasStartsWithIt = requires(Iter1 first1, Sent1 last1, Iter2 first2, Sent2 last2) {
33   std::ranges::starts_with(first1, last1, first2, last2);
34 };
35 
36 static_assert(HasStartsWithIt<int*>);
37 static_assert(HasStartsWithIt<ForwardIteratorNotDerivedFrom>);
38 static_assert(HasStartsWithIt<ForwardIteratorNotIncrementable>);
39 static_assert(!HasStartsWithIt<int*, SentinelForNotSemiregular>);
40 static_assert(!HasStartsWithIt<int*, int*, int**>); // not indirectly comparable
41 static_assert(!HasStartsWithIt<int*, SentinelForNotWeaklyEqualityComparableWith>);
42 static_assert(HasStartsWithIt<int*, int*, ForwardIteratorNotDerivedFrom>);
43 static_assert(HasStartsWithIt<int*, int*, ForwardIteratorNotIncrementable>);
44 static_assert(!HasStartsWithIt<int*, int*, int*, SentinelForNotSemiregular>);
45 static_assert(!HasStartsWithIt<int*, int*, int*, SentinelForNotWeaklyEqualityComparableWith>);
46 
47 template <class Range1, class Range2 = UncheckedRange<int*>>
48 concept HasStartsWithR = requires(Range1 range1, Range2 range2) { std::ranges::starts_with(range1, range2); };
49 
50 static_assert(HasStartsWithR<UncheckedRange<int*>>);
51 static_assert(HasStartsWithR<ForwardRangeNotDerivedFrom>);
52 static_assert(!HasStartsWithR<ForwardIteratorNotIncrementable>);
53 static_assert(!HasStartsWithR<ForwardRangeNotSentinelSemiregular>);
54 static_assert(!HasStartsWithR<ForwardRangeNotSentinelEqualityComparableWith>);
55 static_assert(!HasStartsWithR<UncheckedRange<int*>, UncheckedRange<int**>>); // not indirectly comparable
56 static_assert(HasStartsWithR<UncheckedRange<int*>, ForwardRangeNotDerivedFrom>);
57 static_assert(HasStartsWithR<UncheckedRange<int*>, ForwardRangeNotIncrementable>);
58 static_assert(!HasStartsWithR<UncheckedRange<int*>, ForwardRangeNotSentinelSemiregular>);
59 static_assert(!HasStartsWithR<UncheckedRange<int*>, ForwardRangeNotSentinelEqualityComparableWith>);
60 
61 // clang-format off
62 template <class Iter1, class Sent1 = Iter1, class Iter2, class Sent2 = Iter2>
63 constexpr void test_iterators() {
64   {  // simple tests
65     {
66       int a[] = {1, 2, 3, 4, 5, 6};
67       int p[] = {1, 2};
68       std::same_as<bool> decltype(auto) ret =
69         std::ranges::starts_with(Iter1(a), Sent1(Iter1(a + 6)), Iter2(p), Sent2(Iter2(p + 2)));
70       assert(ret);
71     }
72     {
73       int a[]                               = {1, 2, 3, 4, 5, 6};
74       int p[]                               = {1, 2};
75       auto whole                            = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
76       auto prefix                           = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 2)));
77       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(whole, prefix);
78       assert(ret);
79     }
80   }
81 
82   { // prefix doesn't match
83     {
84       int a[] = {1, 2, 3, 4, 5, 6};
85       int p[] = {4, 5, 6};
86       std::same_as<bool> decltype(auto) ret =
87           std::ranges::starts_with(Iter1(a), Sent1(Iter1(a + 6)), Iter2(p), Sent2(Iter2(p + 3)));
88       assert(!ret);
89     }
90     {
91       int a[]                               = {1, 2, 3, 4, 5, 6};
92       int p[]                               = {4, 5, 6};
93       auto whole                            = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
94       auto prefix                           = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 3)));
95       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(whole, prefix);
96       assert(!ret);
97     }
98   }
99 
100   { // range and prefix are identical
101     {
102       int a[] = {1, 2, 3, 4, 5, 6};
103       int p[] = {1, 2, 3, 4, 5, 6};
104       std::same_as<bool> decltype(auto) ret =
105           std::ranges::starts_with(Iter1(a), Sent1(Iter1(a + 6)), Iter2(p), Sent2(Iter2(p + 6)));
106       assert(ret);
107     }
108     {
109       int a[]                               = {1, 2, 3, 4, 5, 6};
110       int p[]                               = {1, 2, 3, 4, 5, 6};
111       auto whole                            = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
112       auto prefix                           = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 6)));
113       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(whole, prefix);
114       assert(ret);
115     }
116   }
117 
118   { // prefix is longer than range
119     {
120       int a[] = {1, 2, 3, 4, 5, 6};
121       int p[] = {1, 2, 3, 4, 5, 6, 7, 8};
122       std::same_as<bool> decltype(auto) ret =
123           std::ranges::starts_with(Iter1(a), Sent1(Iter1(a + 6)), Iter2(p), Sent2(Iter2(p + 8)));
124       assert(!ret);
125     }
126     {
127       int a[]                               = {1, 2, 3, 4, 5, 6};
128       int p[]                               = {1, 2, 3, 4, 5, 6, 7, 8};
129       auto whole                            = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
130       auto prefix                           = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 8)));
131       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(whole, prefix);
132       assert(!ret);
133     }
134   }
135 
136   { // prefix has zero length
137     {
138       int a[] = {1, 2, 3, 4, 5, 6};
139       int p[] = {};
140       std::same_as<bool> decltype(auto) ret =
141           std::ranges::starts_with(Iter1(a), Sent1(Iter1(a + 6)), Iter2(p), Sent2(Iter2(p)));
142       assert(ret);
143     }
144     {
145       int a[]                               = {1, 2, 3, 4, 5, 6};
146       int p[]                               = {};
147       auto whole                            = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
148       auto prefix                           = std::ranges::subrange(Iter2(p), Sent2(Iter2(p)));
149       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(whole, prefix);
150       assert(ret);
151     }
152   }
153 
154   { // range has zero length
155     {
156       int a[] = {};
157       int p[] = {1, 2, 3, 4, 5, 6, 7, 8};
158       std::same_as<bool> decltype(auto) ret =
159           std::ranges::starts_with(Iter1(a), Sent1(Iter1(a)), Iter2(p), Sent2(Iter2(p + 8)));
160       assert(!ret);
161     }
162     {
163       int a[]                               = {};
164       int p[]                               = {1, 2, 3, 4, 5, 6, 7, 8};
165       auto whole                            = std::ranges::subrange(Iter1(a), Sent1(Iter1(a)));
166       auto prefix                           = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 8)));
167       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(whole, prefix);
168       assert(!ret);
169     }
170   }
171 
172   { // check that the predicate is used
173     {
174       int a[] = {11, 8, 3, 4, 0, 6};
175       int p[]                               = {1, 12};
176       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(
177           Iter1(a), Sent1(Iter1(a + 6)), Iter2(p), Sent2(Iter2(p + 2)), [](int l, int r) { return l > r; });
178       assert(!ret);
179     }
180     {
181       int a[]                               = {11, 8, 3, 4, 0, 6};
182       int p[]                               = {1, 12};
183       auto whole                            = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
184       auto prefix                           = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 2)));
185       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(whole, prefix, [](int l, int r) { return l > r; });
186       assert(!ret);
187     }
188   }
189 
190   { // check that the projections are used
191     {
192       int a[]                               = {1, 3, 5, 1, 5, 6};
193       int p[]                               = {2, 3, 4};
194       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(
195           Iter1(a),
196           Sent1(Iter1(a + 6)),
197           Iter2(p),
198           Sent2(Iter2(p + 3)),
199           {},
200           [](int i) { return i + 3; },
201           [](int i) { return i * 2; });
202       assert(ret);
203     }
204     {
205       int a[]                               = {1, 3, 5, 1, 5, 6};
206       int p[]                               = {2, 3, 4};
207       auto whole                            = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
208       auto prefix                           = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 3)));
209       std::same_as<bool> decltype(auto) ret = std::ranges::starts_with(
210           whole, prefix, {}, [](int i) { return i + 3; }, [](int i) { return i * 2; });
211       assert(ret);
212     }
213   }
214 }
215 
216 constexpr bool test() {
217   types::for_each(types::cpp20_input_iterator_list<int*>{}, []<class Iter2>() {
218     types::for_each(types::cpp20_input_iterator_list<int*>{}, []<class Iter1>() {
219       if constexpr (std::forward_iterator<Iter1> && std::forward_iterator<Iter2>)
220         test_iterators<Iter1, Iter1, Iter2, Iter2>();
221       if constexpr (std::forward_iterator<Iter2>)
222         test_iterators<Iter1, sized_sentinel<Iter1>, Iter2, Iter2>();
223       if constexpr (std::forward_iterator<Iter1>)
224         test_iterators<Iter1, Iter1, Iter2, sized_sentinel<Iter2>>();
225       test_iterators<Iter1, sized_sentinel<Iter1>, Iter2, sized_sentinel<Iter2>>();
226     });
227   });
228 
229   { // check that std::invoke is used
230     struct S {
231       int i;
232 
233       constexpr S identity() { return *this; }
234 
235       constexpr bool compare(const S& s) { return i == s.i; }
236     };
237     {
238       S a[]    = {{1}, {2}, {3}, {4}};
239       S p[]    = {{1}, {2}};
240       auto ret = std::ranges::starts_with(a, a + 4, p, p + 2, &S::compare, &S::identity, &S::identity);
241       assert(ret);
242     }
243     {
244       S a[]    = {{1}, {2}, {3}, {4}};
245       S p[]    = {{1}, {2}};
246       auto ret = std::ranges::starts_with(a, p, &S::compare, &S::identity, &S::identity);
247       assert(ret);
248     }
249   }
250 
251   return true;
252 }
253 
254 int main(int, char**) {
255   test();
256   static_assert(test());
257 
258   return 0;
259 }
260