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 <__debug>
15 #include <__function_like.h>
16 #include <__iterator/advance.h>
17 #include <__iterator/concepts.h>
18 #include <__iterator/incrementable_traits.h>
19 #include <__iterator/iterator_traits.h>
20 #include <type_traits>
21 
22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23 #pragma GCC system_header
24 #endif
25 
26 _LIBCPP_BEGIN_NAMESPACE_STD
27 
28 template <class _InputIter>
29 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
30     typename enable_if<__is_cpp17_input_iterator<_InputIter>::value, _InputIter>::type
31     next(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
32   _LIBCPP_ASSERT(__n >= 0 || __is_cpp17_bidirectional_iterator<_InputIter>::value,
33                  "Attempt to next(it, n) with negative n on a non-bidirectional iterator");
34 
35   _VSTD::advance(__x, __n);
36   return __x;
37 }
38 
39 #if !defined(_LIBCPP_HAS_NO_RANGES)
40 
41 // [range.iter.op.next]
42 
43 namespace ranges {
44 namespace __next {
45 
46 struct __fn final : private __function_like {
47   _LIBCPP_HIDE_FROM_ABI
48   constexpr explicit __fn(__tag __x) noexcept : __function_like(__x) {}
49 
50   template <input_or_output_iterator _Ip>
51   _LIBCPP_HIDE_FROM_ABI
52   constexpr _Ip operator()(_Ip __x) const {
53     ++__x;
54     return __x;
55   }
56 
57   template <input_or_output_iterator _Ip>
58   _LIBCPP_HIDE_FROM_ABI
59   constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
60     ranges::advance(__x, __n);
61     return __x;
62   }
63 
64   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
65   _LIBCPP_HIDE_FROM_ABI
66   constexpr _Ip operator()(_Ip __x, _Sp __bound) const {
67     ranges::advance(__x, __bound);
68     return __x;
69   }
70 
71   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
72   _LIBCPP_HIDE_FROM_ABI
73   constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Sp __bound) const {
74     ranges::advance(__x, __n, __bound);
75     return __x;
76   }
77 };
78 
79 } // namespace __next
80 
81 inline namespace __cpo {
82   inline constexpr auto next = __next::__fn(__function_like::__tag());
83 } // namespace __cpo
84 } // namespace ranges
85 
86 #endif // !defined(_LIBCPP_HAS_NO_RANGES)
87 
88 _LIBCPP_END_NAMESPACE_STD
89 
90 #endif // _LIBCPP___ITERATOR_NEXT_H
91