1 files changed, 87 insertions, 0 deletions
diff --git a/libcxx/include/__iterator/next.h b/libcxx/include/__iterator/next.h
new file mode 100644
index 000000000000..1eecaa9750ba
--- /dev/null
+++ b/libcxx/include/__iterator/next.h
@@ -0,0 +1,87 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ITERATOR_NEXT_H
+#define _LIBCPP___ITERATOR_NEXT_H
+
+#include <__config>
+#include <__debug>
+#include <__function_like.h>
+#include <__iterator/advance.h>
+#include <__iterator/concepts.h>
+#include <__iterator/incrementable_traits.h>
+#include <__iterator/iterator_traits.h>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _InputIter>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    typename enable_if<__is_cpp17_input_iterator<_InputIter>::value, _InputIter>::type
+    next(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
+  _LIBCPP_ASSERT(__n >= 0 || __is_cpp17_bidirectional_iterator<_InputIter>::value,
+                 "Attempt to next(it, n) with negative n on a non-bidirectional iterator");
+
+  _VSTD::advance(__x, __n);
+  return __x;
+}
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+namespace ranges {
+struct __next_fn final : private __function_like {
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr explicit __next_fn(__tag __x) noexcept : __function_like(__x) {}
+
+  template <input_or_output_iterator _Ip>
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr _Ip operator()(_Ip __x) const {
+    ++__x;
+    return __x;
+  }
+
+  template <input_or_output_iterator _Ip>
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
+    ranges::advance(__x, __n);
+    return __x;
+  }
+
+  template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr _Ip operator()(_Ip __x, _Sp __bound) const {
+    ranges::advance(__x, __bound);
+    return __x;
+  }
+
+  template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Sp __bound) const {
+    ranges::advance(__x, __n, __bound);
+    return __x;
+  }
+};
+
+inline constexpr auto next = __next_fn(__function_like::__tag());
+} // namespace ranges
+
+#endif // !defined(_LIBCPP_HAS_NO_RANGES)
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___ITERATOR_PRIMITIVES_H