[libcxx-commits] [libcxx] [libc++][ranges] P2116R9: Implements `views::enumerate` (PR #73617)

via libcxx-commits libcxx-commits at lists.llvm.org
Mon Nov 27 23:34:04 PST 2023


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Hristo Hristov (H-G-Hristov)

<details>
<summary>Changes</summary>



---

Patch is 111.99 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/73617.diff


41 Files Affected:

- (modified) libcxx/docs/FeatureTestMacroTable.rst (+2) 
- (modified) libcxx/docs/Status/Cxx23Papers.csv (+1-1) 
- (modified) libcxx/docs/Status/Cxx2cIssues.csv (+2-2) 
- (modified) libcxx/docs/Status/RangesViews.csv (+1-1) 
- (modified) libcxx/include/CMakeLists.txt (+1) 
- (added) libcxx/include/__ranges/enumerate_view.h (+333) 
- (modified) libcxx/include/module.modulemap.in (+1) 
- (modified) libcxx/include/ranges (+12) 
- (modified) libcxx/include/version (+2) 
- (modified) libcxx/modules/std/ranges.inc (+10-3) 
- (modified) libcxx/test/std/language.support/support.limits/support.limits.general/ranges.version.compile.pass.cpp (+31) 
- (modified) libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp (+31) 
- (modified) libcxx/test/std/ranges/iterator_robust_against_adl.compile.pass.cpp (+1) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/adaptor.pass.cpp (+128) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/base.pass.cpp (+85) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/begin.pass.cpp (+129) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/ctad.compile.pass.cpp (+46) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/ctor.base.pass.cpp (+55) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/ctor.default.pass.cpp (+81) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/enable_borrowed_range.compile.pass.cpp (+35) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/end.pass.cpp (+114) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/arithmetic.pass.cpp (+127) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/base.pass.cpp (+81) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/compare.three_way.pass.cpp (+107) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/ctor.convert.pass.cpp (+84) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/ctor.default.pass.cpp (+69) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/deref.pass.cpp (+101) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/equal.pass.cpp (+97) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/index.pass.cpp (+95) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/iter_move.pass.cpp (+75) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/subscript.pass.cpp (+77) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/iterator/types.compile.pass.cpp (+112) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/sentinel/base.pass.cpp (+62) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/sentinel/ctor.convert.pass.cpp (+75) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/sentinel/ctor.default.pass.cpp (+76) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/sentinel/equal.pass.cpp (+71) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/sentinel/minus.pass.cpp (+253) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/size.pass.cpp (+54) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/types.h (+136) 
- (added) libcxx/test/std/ranges/range.adaptors/range.enumerate/types_iterators.h (+109) 
- (modified) libcxx/utils/generate_feature_test_macro_components.py (+5) 


``````````diff
diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index 3b2dff3108b0f60..cd1190e25bfe176 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -354,6 +354,8 @@ Status
     --------------------------------------------------- -----------------
     ``__cpp_lib_ranges_chunk_by``                       ``202202L``
     --------------------------------------------------- -----------------
+    ``__cpp_lib_ranges_enumerate``                      ``202302L``
+    --------------------------------------------------- -----------------
     ``__cpp_lib_ranges_iota``                           *unimplemented*
     --------------------------------------------------- -----------------
     ``__cpp_lib_ranges_join_with``                      *unimplemented*
diff --git a/libcxx/docs/Status/Cxx23Papers.csv b/libcxx/docs/Status/Cxx23Papers.csv
index 5cc9e488297b9f7..5083a26e4d21b97 100644
--- a/libcxx/docs/Status/Cxx23Papers.csv
+++ b/libcxx/docs/Status/Cxx23Papers.csv
@@ -105,7 +105,7 @@
 "","","","","","",""
 "`P0290R4 <https://wg21.link/P0290R4>`__","LWG", "``apply()`` for ``synchronized_value<T>``","February 2023","","","|concurrency TS|"
 "`P2770R0 <https://wg21.link/P2770R0>`__","LWG", "Stashing stashing ``iterators`` for proper flattening","February 2023","|In Progress|","","|ranges|"
-"`P2164R9 <https://wg21.link/P2164R9>`__","LWG", "``views::enumerate``","February 2023","","","|ranges|"
+"`P2164R9 <https://wg21.link/P2164R9>`__","LWG", "``views::enumerate``","February 2023","|Complete|","18.0","|ranges|"
 "`P2711R1 <https://wg21.link/P2711R1>`__","LWG", "Making multi-param constructors of ``views`` ``explicit``","February 2023","|In Progress| [#note-P2711R1]_","","|ranges|"
 "`P2609R3 <https://wg21.link/P2609R3>`__","LWG", "Relaxing Ranges Just A Smidge","February 2023","","","|ranges|"
 "`P2713R1 <https://wg21.link/P2713R1>`__","LWG", "Escaping improvements in ``std::format``","February 2023","","","|format|"
diff --git a/libcxx/docs/Status/Cxx2cIssues.csv b/libcxx/docs/Status/Cxx2cIssues.csv
index fe0f13f6e8cb2c2..d12dc23cb4a8ca3 100644
--- a/libcxx/docs/Status/Cxx2cIssues.csv
+++ b/libcxx/docs/Status/Cxx2cIssues.csv
@@ -8,8 +8,8 @@
 "`3903 <https://wg21.link/LWG3903>`__","span destructor is redundantly noexcept","Varna June 2023","|Complete|","7.0",""
 "`3904 <https://wg21.link/LWG3904>`__","``lazy_split_view::outer-iterator``'s const-converting constructor isn't setting ``trailing_empty_``","Varna June 2023","","","|ranges|"
 "`3905 <https://wg21.link/LWG3905>`__","Type of ``std::fexcept_t``","Varna June 2023","|Complete|","3.4",""
-"`3912 <https://wg21.link/LWG3912>`__","``enumerate_view::iterator::operator-`` should be ``noexcept``","Varna June 2023","","","|ranges|"
-"`3914 <https://wg21.link/LWG3914>`__","Inconsistent template-head of ``ranges::enumerate_view``","Varna June 2023","","","|ranges|"
+"`3912 <https://wg21.link/LWG3912>`__","``enumerate_view::iterator::operator-`` should be ``noexcept``","Varna June 2023","|Complete|","18.0","|ranges|"
+"`3914 <https://wg21.link/LWG3914>`__","Inconsistent template-head of ``ranges::enumerate_view``","Varna June 2023","|Complete|","18.0","|ranges|"
 "`3915 <https://wg21.link/LWG3915>`__","Redundant paragraph about expression variations","Varna June 2023","","","|ranges|"
 "`3925 <https://wg21.link/LWG3925>`__","Concept ``formattable``'s definition is incorrect","Varna June 2023","|Complete|","17.0","|format|"
 "`3927 <https://wg21.link/LWG3927>`__","Unclear preconditions for ``operator[]`` for sequence containers","Varna June 2023","|Nothing To Do|","",""
diff --git a/libcxx/docs/Status/RangesViews.csv b/libcxx/docs/Status/RangesViews.csv
index f141656eb131a26..581596724878b25 100644
--- a/libcxx/docs/Status/RangesViews.csv
+++ b/libcxx/docs/Status/RangesViews.csv
@@ -35,4 +35,4 @@ C++23,`chunk_by <https://wg21.link/P2443R1>`_,Jakub Mazurkiewicz,`D144767 <https
 C++23,`as_const <https://wg21.link/P2278R4>`_,Unassigned,No patch yet,Not started
 C++23,`as_rvalue <https://wg21.link/P2446R2>`_,Nikolas Klauser,`D137637 <https://llvm.org/D137637>`_,✅
 C++23,`stride <https://wg21.link/P1899R3>`_,Hristo Hristov and Will Hawkins,`D156924 <https://llvm.org/D156924>`_,In Progress
-C++23,`enumerate <https://wg21.link/P2164R9>`_,Hristo Hristov,`D157193 <https://reviews.llvm.org/D157193>`_,In Progress
+C++23,`enumerate <https://wg21.link/P2164R9>`_,Hristo Hristov,`D157193 <https://reviews.llvm.org/D157193>`_,✅
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index b0bc3718576f66b..eca80630bb1c1ef 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -622,6 +622,7 @@ set(files
   __ranges/empty_view.h
   __ranges/enable_borrowed_range.h
   __ranges/enable_view.h
+  __ranges/enumerate_view.h
   __ranges/filter_view.h
   __ranges/from_range.h
   __ranges/iota_view.h
diff --git a/libcxx/include/__ranges/enumerate_view.h b/libcxx/include/__ranges/enumerate_view.h
new file mode 100644
index 000000000000000..77b29837ba54603
--- /dev/null
+++ b/libcxx/include/__ranges/enumerate_view.h
@@ -0,0 +1,333 @@
+// -*- 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___RANGES_ENUMERATE_VIEW_H
+#define _LIBCPP___RANGES_ENUMERATE_VIEW_H
+
+#include <__concepts/convertible_to.h>
+#include <__config>
+#include <__iterator/concepts.h>
+#include <__iterator/distance.h>
+#include <__iterator/iter_move.h>
+#include <__iterator/iterator_traits.h>
+#include <__ranges/access.h>
+#include <__ranges/all.h>
+#include <__ranges/concepts.h>
+#include <__ranges/enable_borrowed_range.h>
+#include <__ranges/range_adaptor.h>
+#include <__ranges/size.h>
+#include <__ranges/view_interface.h>
+#include <__type_traits/maybe_const.h>
+#include <__utility/forward.h>
+#include <__utility/move.h>
+#include <tuple>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 23
+
+namespace ranges {
+
+// [concept.object]
+
+template <class _Rp>
+concept __range_with_movable_references =
+    ranges::input_range<_Rp> && std::move_constructible<ranges::range_reference_t<_Rp>> &&
+    std::move_constructible<ranges::range_rvalue_reference_t<_Rp>>;
+
+// [range.enumerate.view]
+
+template <view _View>
+  requires __range_with_movable_references<_View>
+class enumerate_view : public view_interface<enumerate_view<_View>> {
+  _View __base_ = _View();
+
+  // [range.enumerate.iterator]
+  template <bool _Const>
+  class __iterator;
+
+  // [range.enumerate.sentinel]
+  template <bool _Const>
+  class __sentinel;
+
+  template <bool _AnyConst>
+  _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __get_current(const __iterator<_AnyConst>& __iter) {
+    return (__iter.__current_);
+  }
+
+public:
+  _LIBCPP_HIDE_FROM_ABI constexpr enumerate_view()
+    requires(default_initializable<_View>)
+  = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit enumerate_view(_View __base) : __base_(std::move(__base)){};
+
+  _LIBCPP_HIDE_FROM_ABI constexpr auto begin()
+    requires(!__simple_view<_View>)
+  {
+    return __iterator<false>(ranges::begin(__base_), 0);
+  }
+  _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
+    requires __range_with_movable_references<const _View>
+  {
+    return __iterator<true>(ranges::begin(__base_), 0);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr auto end()
+    requires(!__simple_view<_View>)
+  {
+    if constexpr (common_range<_View> && sized_range<_View>)
+      return __iterator<false>(ranges::end(__base_), ranges::distance(__base_));
+    else
+      return __sentinel<false>(ranges::end(__base_));
+  }
+  _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
+    requires __range_with_movable_references<const _View>
+  {
+    if constexpr (common_range<const _View> && sized_range<const _View>)
+      return __iterator<true>(ranges::end(__base_), ranges::distance(__base_));
+    else
+      return __sentinel<true>(ranges::end(__base_));
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr auto size()
+    requires sized_range<_View>
+  {
+    return ranges::size(__base_);
+  }
+  _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
+    requires sized_range<const _View>
+  {
+    return ranges::size(__base_);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
+    requires copy_constructible<_View>
+  {
+    return __base_;
+  }
+  _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
+};
+
+template <class _Range>
+enumerate_view(_Range&&) -> enumerate_view<views::all_t<_Range>>;
+
+// [range.enumerate.iterator]
+
+template <view _View>
+  requires __range_with_movable_references<_View>
+template <bool _Const>
+class enumerate_view<_View>::__iterator {
+  using _Base = __maybe_const<_Const, _View>;
+
+  static consteval auto __get_iterator_concept() {
+    if constexpr (random_access_range<_Base>) {
+      return random_access_iterator_tag{};
+    } else if constexpr (bidirectional_range<_Base>) {
+      return bidirectional_iterator_tag{};
+    } else if constexpr (forward_range<_Base>) {
+      return forward_iterator_tag{};
+    } else {
+      return input_iterator_tag{};
+    }
+  }
+
+  friend class enumerate_view<_View>;
+
+public:
+  using iterator_category = input_iterator_tag;
+  using iterator_concept  = decltype(__get_iterator_concept());
+  using difference_type   = range_difference_t<_Base>;
+  using value_type        = tuple<difference_type, range_value_t<_Base>>;
+
+private:
+  using __reference_type       = tuple<difference_type, range_reference_t<_Base>>;
+  iterator_t<_Base> __current_ = iterator_t<_Base>();
+  difference_type __pos_       = 0;
+
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit __iterator(iterator_t<_Base> __current, difference_type __pos)
+      : __current_(std::move(__current)), __pos_(__pos) {}
+
+public:
+  _LIBCPP_HIDE_FROM_ABI __iterator()
+    requires(default_initializable<iterator_t<_Base>>)
+  = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr __iterator(__iterator<!_Const> __i)
+    requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
+      : __current_(std::move(__i.__current_)), __pos_(__i.__pos_) {}
+
+  _LIBCPP_HIDE_FROM_ABI constexpr const iterator_t<_Base>& base() const& noexcept { return __current_; }
+  _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() && { return std::move(__current_); }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr difference_type index() const noexcept { return __pos_; }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr auto operator*() const { return __reference_type(__pos_, *__current_); }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
+    ++__current_;
+    ++__pos_;
+    return *this;
+  }
+  _LIBCPP_HIDE_FROM_ABI constexpr void operator++(int) { return ++*this; }
+  _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int)
+    requires forward_range<_Base>
+  {
+    auto __temp = *this;
+    ++*this;
+    return __temp;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
+    requires bidirectional_range<_Base>
+  {
+    --__current_;
+    --__pos_;
+    return *this;
+  }
+  _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
+    requires bidirectional_range<_Base>
+  {
+    auto __temp = *this;
+    --*this;
+    return *__temp;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator+=(difference_type __n)
+    requires random_access_range<_Base>
+  {
+    __current_ += __n;
+    __pos_ += __n;
+    return *this;
+  }
+  _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator-=(difference_type __n)
+    requires random_access_range<_Base>
+  {
+    __current_ -= __n;
+    __pos_ -= __n;
+    return *this;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr auto operator[](difference_type __n) const
+    requires random_access_range<_Base>
+  {
+    return __reference_type(__pos_ + __n, __current_[__n]);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, const __iterator& __y) noexcept {
+    return __x.__pos_ == __y.__pos_;
+  }
+  _LIBCPP_HIDE_FROM_ABI friend constexpr strong_ordering
+  operator<=>(const __iterator& __x, const __iterator& __y) noexcept {
+    return __x.__pos_ <=> __y.__pos_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(const __iterator& __i, difference_type __n)
+    requires random_access_range<_Base>
+  {
+    auto __temp = __i;
+    __temp += __n;
+    return __temp;
+  }
+  _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(difference_type __n, const __iterator& __i)
+    requires random_access_range<_Base>
+  {
+    return __i + __n;
+  }
+  _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator-(const __iterator& __i, difference_type __n)
+    requires random_access_range<_Base>
+  {
+    auto __temp = __i;
+    __temp -= __n;
+    return __temp;
+  }
+  _LIBCPP_HIDE_FROM_ABI friend constexpr difference_type
+  operator-(const __iterator& __x, const __iterator& __y) noexcept {
+    return __x.__pos_ - __y.__pos_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr auto iter_move(const __iterator& __i) noexcept(
+      noexcept(ranges::iter_move(__i.__current_)) && is_nothrow_move_constructible_v<range_rvalue_reference_t<_Base>>) {
+    return tuple<difference_type, range_rvalue_reference_t<_Base>>(__i.__pos_, ranges::iter_move(__i.__current_));
+  }
+};
+
+// [range.enumerate.sentinel]
+
+template <view _View>
+  requires __range_with_movable_references<_View>
+template <bool _Const>
+class enumerate_view<_View>::__sentinel {
+  using _Base              = __maybe_const<_Const, _View>;
+  sentinel_t<_Base> __end_ = sentinel_t<_Base>();
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(std::move(__end)) {}
+
+  friend class enumerate_view<_View>;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI __sentinel() = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __other)
+    requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
+      : __end_(std::move(__other.__end_)) {}
+
+  _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }
+
+  template <bool _OtherConst>
+    requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
+    return __get_current(__x) == __y.__end_;
+  }
+
+  template <bool _OtherConst>
+    requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
+  _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
+  operator-(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
+    return __get_current(__x) - __y.__end_;
+  }
+
+  template <bool _OtherConst>
+    requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
+  _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
+  operator-(const __sentinel& __x, const __iterator<_OtherConst>& __y) {
+    return __x.__end_ - __get_current(__y);
+  }
+};
+
+template <class _View>
+constexpr bool enable_borrowed_range<enumerate_view<_View>> = enable_borrowed_range<_View>;
+
+namespace views {
+namespace __enumerate {
+
+struct __fn : __range_adaptor_closure<__fn> {
+  template <class _Range>
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const
+      noexcept(noexcept(/**/ enumerate_view(std::forward<_Range>(__range))))
+          -> decltype(/*--*/ enumerate_view(std::forward<_Range>(__range))) {
+    return /*-------------*/ enumerate_view(std::forward<_Range>(__range));
+  }
+};
+
+} // namespace __enumerate
+
+inline namespace __cpo {
+
+inline constexpr auto enumerate = __enumerate::__fn{};
+
+} // namespace __cpo
+} // namespace views
+} // namespace ranges
+
+#endif // _LIBCPP_STD_VER >= 23
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___RANGES_ENUMERATE_VIEW_H
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index 90381f4f7f720d4..c0949a28b278b5a 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -1663,6 +1663,7 @@ module std_private_ranges_empty                      [system] { header "__ranges
 module std_private_ranges_empty_view                 [system] { header "__ranges/empty_view.h" }
 module std_private_ranges_enable_borrowed_range      [system] { header "__ranges/enable_borrowed_range.h" }
 module std_private_ranges_enable_view                [system] { header "__ranges/enable_view.h" }
+module std_private_ranges_enumerate_view             [system] { header "__ranges/enumerate_view.h" }
 module std_private_ranges_filter_view                [system] {
   header "__ranges/filter_view.h"
   export std_private_ranges_range_adaptor
diff --git a/libcxx/include/ranges b/libcxx/include/ranges
index f71a92f8a660b06..56b3c82daa11811 100644
--- a/libcxx/include/ranges
+++ b/libcxx/include/ranges
@@ -314,6 +314,17 @@ namespace std::ranges {
 
   namespace views { template<class T> inline constexpr unspecified istream = unspecified; }
 
+  // [range.enumerate], enumerate view
+  template<view View>
+    requires see below
+  class enumerate_view;                                                             // since C++23
+
+  template<class View>
+    constexpr bool enable_borrowed_range<enumerate_view<View>> =                    // since C++23
+      enable_borrowed_range<View>;
+
+  namespace views { inline constexpr unspecified enumerate = unspecified; }         // since C++23
+
   // [range.zip], zip view
   template<input_range... Views>
     requires (view<Views> && ...) && (sizeof...(Views) > 0)
@@ -393,6 +404,7 @@ namespace std {
 #include <__ranges/empty_view.h>
 #include <__ranges/enable_borrowed_range.h>
 #include <__ranges/enable_view.h>
+#include <__ranges/enumerate_view.h>
 #include <__ranges/filter_view.h>
 #include <__ranges/from_range.h>
 #include <__ranges/iota_view.h>
diff --git a/libcxx/include/version b/libcxx/include/version
index ef01af753298222..ed6c2aa9fcd42fa 100644
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -170,6 +170,7 @@ __cpp_lib_ranges_as_const                               202207L <ranges>
 __cpp_lib_ranges_as_rvalue                              202207L <ranges>
 __cpp_lib_ranges_chunk                                  202202L <ranges>
 __cpp_lib_ranges_chunk_by                               202202L <ranges>
+__cpp_lib_ranges_enumerate                              202302L <ranges>
 __cpp_lib_ranges_iota                                   202202L <numeric>
 __cpp_lib_ranges_join_with                              202202L <ranges>
 __cpp_lib_ranges_repeat                                 202207L <ranges>
@@ -461,6 +462,7 @@ __cpp_lib_within_lifetime                               202306L <type_traits>
 # define __cpp_lib_ranges_as_rvalue                     202207L
 // # define __cpp_lib_ranges_chunk                         202202L
 # define __cpp_lib_ranges_chunk_by                      202202L
+# define __cpp_lib_ranges_enumerate                     202302L
 // # define __cpp_lib_ranges_iota                          202202L
 // # define __cpp_lib_ranges_join_with                     202202L
 # define __cpp_lib_ranges_repeat                        202207L
diff --git a/libcxx/modules/std/ranges.inc b/libcxx/modules/std/ranges.inc
index a883103d812588b..5b97f02c56a4957 100644
--- a/libcxx/modules/std/ranges.inc
+++ b/libcxx/modules/std/ranges.inc
@@ -320,9 +320,8 @@ export namespace std {
     namespace views {
       using std::ranges::views::chunk_by;
     }
-#endif // _LIBCPP_STD_VER >= 23
 
-#if 0
+#  if 0
     // [range.stride], stride view
     using std::ranges::stride_view;
 
@@ -335,7 +334,15 @@ export namespace std {
     namespace views {
       using std::ranges::views::cartesian_product;
     }
-#endif
+#  endif
+
+    // [range.enumerate]
+    using std::ranges::enumerate_view;
+
+    namespace views {
+      using std::ranges::views::enumerate;
+    }
+#end...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/73617


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