v1/__iterator/next.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___ITERATOR_NEXT_H
0011 #define _LIBCPP___ITERATOR_NEXT_H
0012
0013 #include <__assert>
0014 #include <__config>
0015 #include <__iterator/advance.h>
0016 #include <__iterator/concepts.h>
0017 #include <__iterator/incrementable_traits.h>
0018 #include <__iterator/iterator_traits.h>
0019 #include <__type_traits/enable_if.h>
0020
0021 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0022 #  pragma GCC system_header
0023 #endif
0024
0025 _LIBCPP_BEGIN_NAMESPACE_STD
0026
0027 template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
0028 [[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _InputIter
0029 next(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
0030   // Calling `advance` with a negative value on a non-bidirectional iterator is a no-op in the current implementation.
0031   // Note that this check duplicates the similar check in `std::advance`.
0032   _LIBCPP_ASSERT_PEDANTIC(__n >= 0 || __has_bidirectional_iterator_category<_InputIter>::value,
0033                           "Attempt to next(it, n) with negative n on a non-bidirectional iterator");
0034
0035   std::advance(__x, __n);
0036   return __x;
0037 }
0038
0039 #if _LIBCPP_STD_VER >= 20
0040
0041 // [range.iter.op.next]
0042
0043 namespace ranges {
0044 struct __next {
0045   template <input_or_output_iterator _Ip>
0046   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x) const {
0047     ++__x;
0048     return __x;
0049   }
0050
0051   template <input_or_output_iterator _Ip>
0052   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
0053     ranges::advance(__x, __n);
0054     return __x;
0055   }
0056
0057   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
0058   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, _Sp __bound_sentinel) const {
0059     ranges::advance(__x, __bound_sentinel);
0060     return __x;
0061   }
0062
0063   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
0064   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip
0065   operator()(_Ip __x, iter_difference_t<_Ip> __n, _Sp __bound_sentinel) const {
0066     ranges::advance(__x, __n, __bound_sentinel);
0067     return __x;
0068   }
0069 };
0070
0071 inline namespace __cpo {
0072 inline constexpr auto next = __next{};
0073 } // namespace __cpo
0074 } // namespace ranges
0075
0076 #endif // _LIBCPP_STD_VER >= 20
0077
0078 _LIBCPP_END_NAMESPACE_STD
0079
0080 #endif // _LIBCPP___ITERATOR_NEXT_H