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 // <iterator>
10 
11 // template <InputIterator Iter>
12 //   Iter next(Iter x, Iter::difference_type n = 1);
13 
14 // LWG #2353 relaxed the requirement on next from ForwardIterator to InputIterator
15 
16 #include <iterator>
17 #include <cassert>
18 
19 #include "test_macros.h"
20 #include "test_iterators.h"
21 
22 template <class It>
23 void
24 test(It i, typename std::iterator_traits<It>::difference_type n, It x)
25 {
26     assert(std::next(i, n) == x);
27 
28     It (*next)(It, typename std::iterator_traits<It>::difference_type) = std::next;
29     assert(next(i, n) == x);
30 }
31 
32 template <class It>
33 void
34 test(It i, It x)
35 {
36     assert(std::next(i) == x);
37 }
38 
39 #if TEST_STD_VER > 14
40 template <class It>
41 constexpr bool
42 constexpr_test(It i, typename std::iterator_traits<It>::difference_type n, It x)
43 {
44     return std::next(i, n) == x;
45 }
46 
47 template <class It>
48 constexpr bool
49 constexpr_test(It i, It x)
50 {
51     return std::next(i) == x;
52 }
53 #endif
54 
55 int main(int, char**)
56 {
57     {
58     const char* s = "1234567890";
59     test(input_iterator<const char*>(s),             10, input_iterator<const char*>(s+10));
60     test(forward_iterator<const char*>(s),           10, forward_iterator<const char*>(s+10));
61     test(bidirectional_iterator<const char*>(s),     10, bidirectional_iterator<const char*>(s+10));
62     test(bidirectional_iterator<const char*>(s+10), -10, bidirectional_iterator<const char*>(s));
63     test(random_access_iterator<const char*>(s),     10, random_access_iterator<const char*>(s+10));
64     test(random_access_iterator<const char*>(s+10), -10, random_access_iterator<const char*>(s));
65     test(s, 10, s+10);
66 
67     test(input_iterator<const char*>(s), input_iterator<const char*>(s+1));
68     test(forward_iterator<const char*>(s), forward_iterator<const char*>(s+1));
69     test(bidirectional_iterator<const char*>(s), bidirectional_iterator<const char*>(s+1));
70     test(random_access_iterator<const char*>(s), random_access_iterator<const char*>(s+1));
71     test(s, s+1);
72     }
73 #if TEST_STD_VER > 14
74     {
75     constexpr const char* s = "1234567890";
76     static_assert( constexpr_test(input_iterator<const char*>(s),             10, input_iterator<const char*>(s+10)), "" );
77     static_assert( constexpr_test(forward_iterator<const char*>(s),           10, forward_iterator<const char*>(s+10)), "" );
78     static_assert( constexpr_test(bidirectional_iterator<const char*>(s),     10, bidirectional_iterator<const char*>(s+10)), "" );
79     static_assert( constexpr_test(bidirectional_iterator<const char*>(s+10), -10, bidirectional_iterator<const char*>(s)), "" );
80     static_assert( constexpr_test(random_access_iterator<const char*>(s),     10, random_access_iterator<const char*>(s+10)), "" );
81     static_assert( constexpr_test(random_access_iterator<const char*>(s+10), -10, random_access_iterator<const char*>(s)), "" );
82     static_assert( constexpr_test(s, 10, s+10), "" );
83 
84     static_assert( constexpr_test(input_iterator<const char*>(s), input_iterator<const char*>(s+1)), "" );
85     static_assert( constexpr_test(forward_iterator<const char*>(s), forward_iterator<const char*>(s+1)), "" );
86     static_assert( constexpr_test(bidirectional_iterator<const char*>(s), bidirectional_iterator<const char*>(s+1)), "" );
87     static_assert( constexpr_test(random_access_iterator<const char*>(s), random_access_iterator<const char*>(s+1)), "" );
88     static_assert( constexpr_test(s, s+1), "" );
89     }
90 #endif
91 
92   return 0;
93 }
94