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 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17
  29     _InputIter
  30     next(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
  31   _LIBCPP_ASSERT_UNCATEGORIZED(__n >= 0 || __has_bidirectional_iterator_category<_InputIter>::value,
  32                                "Attempt to next(it, n) with negative n on a non-bidirectional iterator");
  33
  34   _VSTD::advance(__x, __n);
  35   return __x;
  36 }
  37
  38 #if _LIBCPP_STD_VER >= 20
  39
  40 // [range.iter.op.next]
  41
  42 namespace ranges {
  43 namespace __next {
  44
  45 struct __fn {
  46   template <input_or_output_iterator _Ip>
  47   _LIBCPP_HIDE_FROM_ABI
  48   constexpr _Ip operator()(_Ip __x) const {
  49     ++__x;
  50     return __x;
  51   }
  52
  53   template <input_or_output_iterator _Ip>
  54   _LIBCPP_HIDE_FROM_ABI
  55   constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
  56     ranges::advance(__x, __n);
  57     return __x;
  58   }
  59
  60   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
  61   _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, _Sp __bound_sentinel) const {
  62     ranges::advance(__x, __bound_sentinel);
  63     return __x;
  64   }
  65
  66   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
  67   _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Sp __bound_sentinel) const {
  68     ranges::advance(__x, __n, __bound_sentinel);
  69     return __x;
  70   }
  71 };
  72
  73 } // namespace __next
  74
  75 inline namespace __cpo {
  76   inline constexpr auto next = __next::__fn{};
  77 } // namespace __cpo
  78 } // namespace ranges
  79
  80 #endif // _LIBCPP_STD_VER >= 20
  81
  82 _LIBCPP_END_NAMESPACE_STD
  83
  84 #endif // _LIBCPP___ITERATOR_NEXT_H