[libcxx][iterator] adds `std::ranges::prev`
Implements part of P0896 'The One Ranges Proposal'.
Implements [range.iter.op.prev].
Depends on D102563.
Differential Revision: https://reviews.llvm.org/D102564
NOKEYCHECK=True
GitOrigin-RevId: 0dc7fd1bc1670e9f7e58b08b51b478a6334c8b01
diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index 0dd1d9c..f752fab 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -20,6 +20,7 @@
__iterator/iter_move.h
__iterator/iterator_traits.h
__iterator/next.h
+ __iterator/prev.h
__iterator/readable_traits.h
__libcpp_version
__locale
diff --git a/include/__iterator/prev.h b/include/__iterator/prev.h
new file mode 100644
index 0000000..a6d2f59
--- /dev/null
+++ b/include/__iterator/prev.h
@@ -0,0 +1,62 @@
+// -*- 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_PREV_H
+#define _LIBCPP___ITERATOR_PREV_H
+
+#include <__config>
+#include <__function_like.h>
+#include <__iterator/advance.h>
+#include <__iterator/concepts.h>
+#include <__iterator/incrementable_traits.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+namespace ranges {
+struct __prev_fn final : private __function_like {
+ constexpr explicit __prev_fn(__tag __x) noexcept : __function_like(__x) {}
+
+ template <bidirectional_iterator _Ip>
+ constexpr _Ip operator()(_Ip __x) const {
+ --__x;
+ return __x;
+ }
+
+ template <bidirectional_iterator _Ip>
+ constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
+ ranges::advance(__x, -__n);
+ return __x;
+ }
+
+ template <bidirectional_iterator _Ip>
+ constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Ip __bound) const {
+ ranges::advance(__x, -__n, __bound);
+ return __x;
+ }
+};
+
+inline constexpr auto prev = __prev_fn(__function_like::__tag());
+} // namespace ranges
+
+#endif // !defined(_LIBCPP_HAS_NO_RANGES)
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___ITERATOR_PREV_H
diff --git a/include/iterator b/include/iterator
index a094049..8dbcc9d 100644
--- a/include/iterator
+++ b/include/iterator
@@ -489,6 +489,7 @@
#include <__iterator/iter_move.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/next.h>
+#include <__iterator/prev.h>
#include <__iterator/readable_traits.h>
#include <__memory/addressof.h>
#include <__memory/pointer_traits.h>