[libcxx-commits] [libcxx] 45c4124 - [libc++][ranges] P3060R3: Add `std::views::indices(n)` (#146823)
via libcxx-commits
libcxx-commits at lists.llvm.org
Mon Oct 6 08:13:30 PDT 2025
Author: Hristo Hristov
Date: 2025-10-06T18:13:25+03:00
New Revision: 45c41247f82e5691425542de829d568cdc2fb580
URL: https://github.com/llvm/llvm-project/commit/45c41247f82e5691425542de829d568cdc2fb580
DIFF: https://github.com/llvm/llvm-project/commit/45c41247f82e5691425542de829d568cdc2fb580.diff
LOG: [libc++][ranges] P3060R3: Add `std::views::indices(n)` (#146823)
Implements [P3060R3](https://wg21.link/P3060R3)
Closes #148175
# References
- https://github.com/cplusplus/draft/issues/7966
- https://github.com/cplusplus/draft/pull/8006
- https://wg21.link/customization.point.object
- https://wg21.link/range.iota.overview
- https://wg21.link/ranges.syn
---------
Co-authored-by: Hristo Hristov <zingam at outlook.com>
Co-authored-by: A. Jiang <de34 at live.cn>
Added:
libcxx/test/std/ranges/range.factories/range.iota.view/indices.pass.cpp
Modified:
libcxx/docs/FeatureTestMacroTable.rst
libcxx/docs/ReleaseNotes/22.rst
libcxx/docs/Status/Cxx2cPapers.csv
libcxx/include/__ranges/iota_view.h
libcxx/include/ranges
libcxx/include/version
libcxx/modules/std/ranges.inc
libcxx/test/std/language.support/support.limits/support.limits.general/ranges.version.compile.pass.cpp
libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
libcxx/test/std/library/description/conventions/customization.point.object/cpo.compile.pass.cpp
libcxx/utils/generate_feature_test_macro_components.py
Removed:
################################################################################
diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index 3c7175c73f21e..c7f01e6868395 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -488,6 +488,8 @@ Status
---------------------------------------------------------- -----------------
``__cpp_lib_ranges_concat`` *unimplemented*
---------------------------------------------------------- -----------------
+ ``__cpp_lib_ranges_indices`` ``202506L``
+ ---------------------------------------------------------- -----------------
``__cpp_lib_ratio`` ``202306L``
---------------------------------------------------------- -----------------
``__cpp_lib_rcu`` *unimplemented*
diff --git a/libcxx/docs/ReleaseNotes/22.rst b/libcxx/docs/ReleaseNotes/22.rst
index 8d023a14e89e6..ec23ba9d1e3a1 100644
--- a/libcxx/docs/ReleaseNotes/22.rst
+++ b/libcxx/docs/ReleaseNotes/22.rst
@@ -42,6 +42,7 @@ Implemented Papers
is implemented in this release)
- P3044R2: sub-``string_view`` from ``string`` (`Github <https://llvm.org/PR148140>`__)
- P3223R2: Making ``std::istream::ignore`` less surprising (`Github <https://llvm.org/PR148178>`__)
+- P3060R3: Add ``std::views::indices(n)`` (`Github <https://llvm.org/PR148175>`__)
- P3168R2: Give ``std::optional`` Range Support (`Github <https://llvm.org/PR105430>`__)
Improvements and New Features
diff --git a/libcxx/docs/Status/Cxx2cPapers.csv b/libcxx/docs/Status/Cxx2cPapers.csv
index 4e0918b0246c1..69b9984f43ccf 100644
--- a/libcxx/docs/Status/Cxx2cPapers.csv
+++ b/libcxx/docs/Status/Cxx2cPapers.csv
@@ -149,7 +149,7 @@
"`P3503R3 <https://wg21.link/P3503R3>`__","Make type-erased allocator use in ``promise`` and ``packaged_task`` consistent","2025-06 (Sofia)","","","`#148164 <https://github.com/llvm/llvm-project/issues/148164>`__",""
"`P3008R6 <https://wg21.link/P3008R6>`__","Atomic floating-point min/max","2025-06 (Sofia)","","","`#148168 <https://github.com/llvm/llvm-project/issues/148168>`__",""
"`P3111R8 <https://wg21.link/P3111R8>`__","Atomic Reduction Operations","2025-06 (Sofia)","","","`#148174 <https://github.com/llvm/llvm-project/issues/148174>`__",""
-"`P3060R3 <https://wg21.link/P3060R3>`__","Add ``std::views::indices(n)``","2025-06 (Sofia)","","","`#148175 <https://github.com/llvm/llvm-project/issues/148175>`__",""
+"`P3060R3 <https://wg21.link/P3060R3>`__","Add ``std::views::indices(n)``","2025-06 (Sofia)","|Complete|","22","`#148175 <https://github.com/llvm/llvm-project/issues/148175>`__",""
"`P2319R5 <https://wg21.link/P2319R5>`__","Prevent ``path`` presentation problems","2025-06 (Sofia)","","","`#148177 <https://github.com/llvm/llvm-project/issues/148177>`__",""
"`P3223R2 <https://wg21.link/P3223R2>`__","Making ``std::istream::ignore`` less surprising","2025-06 (Sofia)","|Complete|","22","`#148178 <https://github.com/llvm/llvm-project/issues/148178>`__",""
"`P2781R9 <https://wg21.link/P2781R9>`__","``std::constant_wrapper``","2025-06 (Sofia)","","","`#148179 <https://github.com/llvm/llvm-project/issues/148179>`__",""
diff --git a/libcxx/include/__ranges/iota_view.h b/libcxx/include/__ranges/iota_view.h
index 32ff3408e54ea..22adc22e69190 100644
--- a/libcxx/include/__ranges/iota_view.h
+++ b/libcxx/include/__ranges/iota_view.h
@@ -393,6 +393,15 @@ struct __fn {
inline namespace __cpo {
inline constexpr auto iota = __iota::__fn{};
} // namespace __cpo
+
+# if _LIBCPP_STD_VER >= 26
+
+inline constexpr auto indices = [](__integer_like auto __size) static {
+ return ranges::views::iota(decltype(__size){}, __size);
+};
+
+# endif
+
} // namespace views
} // namespace ranges
diff --git a/libcxx/include/ranges b/libcxx/include/ranges
index 96d7a6b897188..cfaa66a0831b3 100644
--- a/libcxx/include/ranges
+++ b/libcxx/include/ranges
@@ -267,6 +267,11 @@ namespace std::ranges {
template<class W, class Bound>
inline constexpr bool enable_borrowed_range<iota_view<W, Bound>> = true;
+ namespace views {
+ inline constexpr unspecified iota = unspecified;
+ inline constexpr unspecified indices = unspecified; // Since C++26
+ }
+
// [range.repeat], repeat view
template<class T>
concept integer-like-with-usable-
diff erence-type = // exposition only
diff --git a/libcxx/include/version b/libcxx/include/version
index a132f0808aeb8..99e69299921fa 100644
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -205,6 +205,7 @@ __cpp_lib_ranges_chunk_by 202202L <ranges>
__cpp_lib_ranges_concat 202403L <ranges>
__cpp_lib_ranges_contains 202207L <algorithm>
__cpp_lib_ranges_find_last 202207L <algorithm>
+__cpp_lib_ranges_indices 202506L <ranges>
__cpp_lib_ranges_iota 202202L <numeric>
__cpp_lib_ranges_join_with 202202L <ranges>
__cpp_lib_ranges_repeat 202207L <ranges>
@@ -591,6 +592,7 @@ __cpp_lib_void_t 201411L <type_traits>
# define __cpp_lib_out_ptr 202311L
// # define __cpp_lib_philox_engine 202406L
// # define __cpp_lib_ranges_concat 202403L
+# define __cpp_lib_ranges_indices 202506L
# define __cpp_lib_ratio 202306L
// # define __cpp_lib_rcu 202306L
# define __cpp_lib_reference_wrapper 202403L
diff --git a/libcxx/modules/std/ranges.inc b/libcxx/modules/std/ranges.inc
index 7ede42e4f7b0a..cc7daa3cd1aec 100644
--- a/libcxx/modules/std/ranges.inc
+++ b/libcxx/modules/std/ranges.inc
@@ -114,6 +114,9 @@ export namespace std {
namespace views {
using std::ranges::views::iota;
+#if _LIBCPP_STD_VER >= 26
+ using std::ranges::views::indices;
+#endif
} // namespace views
#if _LIBCPP_STD_VER >= 23
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/ranges.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/ranges.version.compile.pass.cpp
index df19f03e7dba1..5116864879485 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/ranges.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/ranges.version.compile.pass.cpp
@@ -48,6 +48,10 @@
# error "__cpp_lib_ranges_concat should not be defined before c++26"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifdef __cpp_lib_ranges_join_with
# error "__cpp_lib_ranges_join_with should not be defined before c++23"
# endif
@@ -98,6 +102,10 @@
# error "__cpp_lib_ranges_concat should not be defined before c++26"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifdef __cpp_lib_ranges_join_with
# error "__cpp_lib_ranges_join_with should not be defined before c++23"
# endif
@@ -148,6 +156,10 @@
# error "__cpp_lib_ranges_concat should not be defined before c++26"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifdef __cpp_lib_ranges_join_with
# error "__cpp_lib_ranges_join_with should not be defined before c++23"
# endif
@@ -201,6 +213,10 @@
# error "__cpp_lib_ranges_concat should not be defined before c++26"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifdef __cpp_lib_ranges_join_with
# error "__cpp_lib_ranges_join_with should not be defined before c++23"
# endif
@@ -278,6 +294,10 @@
# error "__cpp_lib_ranges_concat should not be defined before c++26"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifndef __cpp_lib_ranges_join_with
# error "__cpp_lib_ranges_join_with should be defined in c++23"
# endif
@@ -400,6 +420,13 @@
# endif
# endif
+# ifndef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should be defined in c++26"
+# endif
+# if __cpp_lib_ranges_indices != 202506L
+# error "__cpp_lib_ranges_indices should have the value 202506L in c++26"
+# endif
+
# ifndef __cpp_lib_ranges_join_with
# error "__cpp_lib_ranges_join_with should be defined in c++26"
# endif
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
index 6aa704a3ead3f..9a8a1da88ee8f 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
@@ -664,6 +664,10 @@
# error "__cpp_lib_ranges_find_last should not be defined before c++23"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifdef __cpp_lib_ranges_iota
# error "__cpp_lib_ranges_iota should not be defined before c++23"
# endif
@@ -1608,6 +1612,10 @@
# error "__cpp_lib_ranges_find_last should not be defined before c++23"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifdef __cpp_lib_ranges_iota
# error "__cpp_lib_ranges_iota should not be defined before c++23"
# endif
@@ -2723,6 +2731,10 @@
# error "__cpp_lib_ranges_find_last should not be defined before c++23"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifdef __cpp_lib_ranges_iota
# error "__cpp_lib_ranges_iota should not be defined before c++23"
# endif
@@ -4111,6 +4123,10 @@
# error "__cpp_lib_ranges_find_last should not be defined before c++23"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifdef __cpp_lib_ranges_iota
# error "__cpp_lib_ranges_iota should not be defined before c++23"
# endif
@@ -5694,6 +5710,10 @@
# error "__cpp_lib_ranges_find_last should have the value 202207L in c++23"
# endif
+# ifdef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should not be defined before c++26"
+# endif
+
# ifndef __cpp_lib_ranges_iota
# error "__cpp_lib_ranges_iota should be defined in c++23"
# endif
@@ -7610,6 +7630,13 @@
# error "__cpp_lib_ranges_find_last should have the value 202207L in c++26"
# endif
+# ifndef __cpp_lib_ranges_indices
+# error "__cpp_lib_ranges_indices should be defined in c++26"
+# endif
+# if __cpp_lib_ranges_indices != 202506L
+# error "__cpp_lib_ranges_indices should have the value 202506L in c++26"
+# endif
+
# ifndef __cpp_lib_ranges_iota
# error "__cpp_lib_ranges_iota should be defined in c++26"
# endif
diff --git a/libcxx/test/std/library/description/conventions/customization.point.object/cpo.compile.pass.cpp b/libcxx/test/std/library/description/conventions/customization.point.object/cpo.compile.pass.cpp
index 49497875dcf95..7e2510f5b5d13 100644
--- a/libcxx/test/std/library/description/conventions/customization.point.object/cpo.compile.pass.cpp
+++ b/libcxx/test/std/library/description/conventions/customization.point.object/cpo.compile.pass.cpp
@@ -89,6 +89,9 @@ static_assert(test(std::ranges::ssize, a));
// views::empty<T> is not a CPO
static_assert(test(std::views::iota, 1));
static_assert(test(std::views::iota, 1, 10));
+#if TEST_STD_VER >= 26
+static_assert(test(std::views::indices, 10));
+#endif
#ifndef TEST_HAS_NO_LOCALIZATION
static_assert(test(std::views::istream<int>, stream));
#endif
diff --git a/libcxx/test/std/ranges/range.factories/range.iota.view/indices.pass.cpp b/libcxx/test/std/ranges/range.factories/range.iota.view/indices.pass.cpp
new file mode 100644
index 0000000000000..d92b6cb876a40
--- /dev/null
+++ b/libcxx/test/std/ranges/range.factories/range.iota.view/indices.pass.cpp
@@ -0,0 +1,97 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: std-at-least-c++26
+
+// ranges
+
+// inline constexpr unspecified indices = unspecified;
+
+#include <cassert>
+#include <cstddef>
+#include <ranges>
+#include <vector>
+
+#include "test_macros.h"
+#define TEST_HAS_NO_INT128 // Size cannot be larger than 64 bits
+#include "type_algorithms.h"
+
+#include "types.h"
+
+// Test SFINAE.
+
+template <typename SizeType>
+concept HasIndices = requires(SizeType s) { std::ranges::views::indices(s); };
+
+struct NotIntegerLike {};
+
+void test_SFINAE() {
+ static_assert(HasIndices<std::size_t>);
+ types::for_each(types::integer_types(), []<typename T> { static_assert(HasIndices<T>); });
+
+ // Non-integer-like types should not satisfy HasIndices
+ static_assert(!HasIndices<bool>);
+ static_assert(!HasIndices<float>);
+ static_assert(!HasIndices<void>);
+ static_assert(!HasIndices<SomeInt>); // Does satisfy is_integer_like, but not the conversion to std::size_t
+ static_assert(!HasIndices<NotIntegerLike>);
+}
+
+constexpr bool test() {
+ {
+ auto indices_view = std::ranges::views::indices(5);
+ static_assert(std::ranges::range<decltype(indices_view)>);
+
+ assert(indices_view.size() == 5);
+
+ assert(indices_view[0] == 0);
+ assert(indices_view[1] == 1);
+ assert(indices_view[2] == 2);
+ assert(indices_view[3] == 3);
+ assert(indices_view[4] == 4);
+ }
+
+ {
+ std::vector v(5, 0);
+
+ auto indices_view = std::ranges::views::indices(std::ranges::size(v));
+ static_assert(std::ranges::range<decltype(indices_view)>);
+
+ assert(indices_view.size() == 5);
+
+ assert(indices_view[0] == 0);
+ assert(indices_view[1] == 1);
+ assert(indices_view[2] == 2);
+ assert(indices_view[3] == 3);
+ assert(indices_view[4] == 4);
+ }
+
+ {
+ std::vector v(5, SomeInt{});
+
+ auto indices_view = std::ranges::views::indices(std::ranges::size(v));
+ static_assert(std::ranges::range<decltype(indices_view)>);
+
+ assert(indices_view.size() == 5);
+
+ assert(indices_view[0] == 0);
+ assert(indices_view[1] == 1);
+ assert(indices_view[2] == 2);
+ assert(indices_view[3] == 3);
+ assert(indices_view[4] == 4);
+ }
+
+ return true;
+}
+
+int main(int, char**) {
+ test();
+ static_assert(test());
+
+ return 0;
+}
diff --git a/libcxx/utils/generate_feature_test_macro_components.py b/libcxx/utils/generate_feature_test_macro_components.py
index 5d469d4914b0b..2d5b66d994da0 100644
--- a/libcxx/utils/generate_feature_test_macro_components.py
+++ b/libcxx/utils/generate_feature_test_macro_components.py
@@ -1113,6 +1113,11 @@ def add_version_header(tc):
"values": {"c++23": 202207},
"headers": ["algorithm"],
},
+ {
+ "name": "__cpp_lib_ranges_indices",
+ "values": {"c++26": 202506},
+ "headers": ["ranges"],
+ },
{
"name": "__cpp_lib_ranges_iota",
"values": {"c++23": 202202},
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