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 <__function_like.h>
15 #include <__iterator/advance.h>
16 #include <__iterator/concepts.h>
17 #include <__iterator/incrementable_traits.h>
18 
19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20 #pragma GCC system_header
21 #endif
22 
23 _LIBCPP_PUSH_MACROS
24 #include <__undef_macros>
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 namespace ranges {
42 struct __next_fn final : private __function_like {
43   constexpr explicit __next_fn(__tag __x) noexcept : __function_like(__x) {}
44 
45   template <input_or_output_iterator _Ip>
46   constexpr _Ip operator()(_Ip __x) const {
47     ++__x;
48     return __x;
49   }
50 
51   template <input_or_output_iterator _Ip>
52   constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
53     ranges::advance(__x, __n);
54     return __x;
55   }
56 
57   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
58   constexpr _Ip operator()(_Ip __x, _Sp __bound) const {
59     ranges::advance(__x, __bound);
60     return __x;
61   }
62 
63   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
64   constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Sp __bound) const {
65     ranges::advance(__x, __n, __bound);
66     return __x;
67   }
68 };
69 
70 inline constexpr auto next = __next_fn(__function_like::__tag());
71 } // namespace ranges
72 
73 #endif // !defined(_LIBCPP_HAS_NO_RANGES)
74 
75 _LIBCPP_END_NAMESPACE_STD
76 
77 _LIBCPP_POP_MACROS
78 
79 #endif // _LIBCPP___ITERATOR_PRIMITIVES_H
80