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); // constexpr in C++17
13
14// LWG #2353 relaxed the requirement on next from ForwardIterator to InputIterator
15
16#include <iterator>
17#include <cassert>
18#include <type_traits>
19
20#include "test_macros.h"
21#include "test_iterators.h"
22
23template <class It>
24TEST_CONSTEXPR_CXX17 void
25check_next_n(It it, typename std::iterator_traits<It>::difference_type n, It result)
26{
27 static_assert(std::is_same<decltype(std::next(it, n)), It>::value, "");
28 assert(std::next(it, n) == result);
29
30 It (*next_ptr)(It, typename std::iterator_traits<It>::difference_type) = std::next;
31 assert(next_ptr(it, n) == result);
32}
33
34template <class It>
35TEST_CONSTEXPR_CXX17 void
36check_next_1(It it, It result)
37{
38 static_assert(std::is_same<decltype(std::next(it)), It>::value, "");
39 assert(std::next(it) == result);
40}
41
42TEST_CONSTEXPR_CXX17 bool tests()
43{
44 const char* s = "1234567890";
45 check_next_n(cpp17_input_iterator<const char*>(s), 10, cpp17_input_iterator<const char*>(s+10));
46 check_next_n(forward_iterator<const char*>(s), 10, forward_iterator<const char*>(s+10));
47 check_next_n(bidirectional_iterator<const char*>(s), 10, bidirectional_iterator<const char*>(s+10));
48 check_next_n(bidirectional_iterator<const char*>(s+10), -10, bidirectional_iterator<const char*>(s));
49 check_next_n(random_access_iterator<const char*>(s), 10, random_access_iterator<const char*>(s+10));
50 check_next_n(random_access_iterator<const char*>(s+10), -10, random_access_iterator<const char*>(s));
51 check_next_n(s, 10, s+10);
52
53 check_next_1(cpp17_input_iterator<const char*>(s), cpp17_input_iterator<const char*>(s+1));
54 check_next_1(forward_iterator<const char*>(s), forward_iterator<const char*>(s+1));
55 check_next_1(bidirectional_iterator<const char*>(s), bidirectional_iterator<const char*>(s+1));
56 check_next_1(random_access_iterator<const char*>(s), random_access_iterator<const char*>(s+1));
57 check_next_1(s, s+1);
58
59 return true;
60}
61
62int main(int, char**)
63{
64 tests();
65#if TEST_STD_VER >= 17
66 static_assert(tests(), "");
67#endif
68 return 0;
69}
70

source code of libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.pass.cpp