libcxx/include/__iterator/next.h

   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
  27 template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
  28 [[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _InputIter
  29 next(_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
  43 namespace ranges {
  44 struct __next {
  45   template <input_or_output_iterator _Ip>
  46   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x) const {
  47     ++__x;
  48     return __x;
  49   }
  50
  51   template <input_or_output_iterator _Ip>
  52   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI 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   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, _Sp __bound_sentinel) const {
  59     ranges::advance(__x, __bound_sentinel);
  60     return __x;
  61   }
  62
  63   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
  64   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip
  65   operator()(_Ip __x, iter_difference_t<_Ip> __n, _Sp __bound_sentinel) const {
  66     ranges::advance(__x, __n, __bound_sentinel);
  67     return __x;
  68   }
  69 };
  70
  71 inline namespace __cpo {
  72 inline constexpr auto next = __next{};
  73 } // namespace __cpo
  74 } // namespace ranges
  75
  76 #endif // _LIBCPP_STD_VER >= 20
  77
  78 _LIBCPP_END_NAMESPACE_STD
  79
  80 #endif // _LIBCPP___ITERATOR_NEXT_H