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 <__config>
14#include <__iterator/advance.h>
15#include <__iterator/concepts.h>
16#include <__iterator/incrementable_traits.h>
17#include <__iterator/iterator_traits.h>
18#include <__type_traits/enable_if.h>
19
20#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21#  pragma GCC system_header
22#endif
23
24_LIBCPP_BEGIN_NAMESPACE_STD
25
26template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
27[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _InputIter
28next(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
29  std::advance(__x, __n);
30  return __x;
31}
32
33#if _LIBCPP_STD_VER >= 20
34
35// [range.iter.op.next]
36
37namespace ranges {
38struct __next {
39  template <input_or_output_iterator _Ip>
40  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x) const {
41    ++__x;
42    return __x;
43  }
44
45  template <input_or_output_iterator _Ip>
46  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
47    ranges::advance(__x, __n);
48    return __x;
49  }
50
51  template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
52  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, _Sp __bound_sentinel) const {
53    ranges::advance(__x, __bound_sentinel);
54    return __x;
55  }
56
57  template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
58  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip
59  operator()(_Ip __x, iter_difference_t<_Ip> __n, _Sp __bound_sentinel) const {
60    ranges::advance(__x, __n, __bound_sentinel);
61    return __x;
62  }
63};
64
65inline namespace __cpo {
66inline constexpr auto next = __next{};
67} // namespace __cpo
68} // namespace ranges
69
70#endif // _LIBCPP_STD_VER >= 20
71
72_LIBCPP_END_NAMESPACE_STD
73
74#endif // _LIBCPP___ITERATOR_NEXT_H