1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___ITERATOR_NEXT_H
11#define _LIBCPP___ITERATOR_NEXT_H
12
13#include <__assert>
14#include <__config>
15#include <__iterator/advance.h>
16#include <__iterator/concepts.h>
17#include <__iterator/incrementable_traits.h>
18#include <__iterator/iterator_traits.h>
19#include <__type_traits/enable_if.h>
20
21#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
22#  pragma GCC system_header
23#endif
24
25_LIBCPP_BEGIN_NAMESPACE_STD
26
27template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
28inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _InputIter
29next(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
30  // Calling `advance` with a negative value on a non-bidirectional iterator is a no-op in the current implementation.
31  // Note that this check duplicates the similar check in `std::advance`.
32  _LIBCPP_ASSERT_PEDANTIC(__n >= 0 || __has_bidirectional_iterator_category<_InputIter>::value,
33                          "Attempt to next(it, n) with negative n on a non-bidirectional iterator");
34
35  std::advance(__x, __n);
36  return __x;
37}
38
39#if _LIBCPP_STD_VER >= 20
40
41// [range.iter.op.next]
42
43namespace ranges {
44namespace __next {
45
46struct __fn {
47  template <input_or_output_iterator _Ip>
48  _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x) const {
49    ++__x;
50    return __x;
51  }
52
53  template <input_or_output_iterator _Ip>
54  _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
55    ranges::advance(__x, __n);
56    return __x;
57  }
58
59  template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
60  _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, _Sp __bound_sentinel) const {
61    ranges::advance(__x, __bound_sentinel);
62    return __x;
63  }
64
65  template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
66  _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Sp __bound_sentinel) const {
67    ranges::advance(__x, __n, __bound_sentinel);
68    return __x;
69  }
70};
71
72} // namespace __next
73
74inline namespace __cpo {
75inline constexpr auto next = __next::__fn{};
76} // namespace __cpo
77} // namespace ranges
78
79#endif // _LIBCPP_STD_VER >= 20
80
81_LIBCPP_END_NAMESPACE_STD
82
83#endif // _LIBCPP___ITERATOR_NEXT_H
84