[libcxx-commits] [libcxx] WIP [libc++][ranges] P3060R3 Add std::views::indices(n) (PR #146823)
via libcxx-commits
libcxx-commits at lists.llvm.org
Thu Jul 3 02:56:18 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: Hristo Hristov (H-G-Hristov)
<details>
<summary>Changes</summary>
Implements [P3060R2](https://wg21.link/ )
# References
- https://github.com/cplusplus/draft/issues/7966
- https://github.com/cplusplus/draft/pull/8006
---
This implements only P3060R2
---
Full diff: https://github.com/llvm/llvm-project/pull/146823.diff
9 Files Affected:
- (modified) libcxx/docs/FeatureTestMacroTable.rst (+2)
- (modified) libcxx/docs/ReleaseNotes/21.rst (+1)
- (modified) libcxx/include/__ranges/iota_view.h (+10)
- (modified) libcxx/include/ranges (+5)
- (modified) libcxx/include/version (+2)
- (modified) libcxx/test/std/language.support/support.limits/support.limits.general/ranges.version.compile.pass.cpp (+27)
- (modified) libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp (+27)
- (added) libcxx/test/std/ranges/range.factories/range.iota.view/indices.pass.cpp (+110)
- (modified) libcxx/utils/generate_feature_test_macro_components.py (+5)
``````````diff
diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index 3c635e5e46bbd..74ec5936f8598 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -484,6 +484,8 @@ 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/21.rst b/libcxx/docs/ReleaseNotes/21.rst
index 08b32bb508dc1..7e525a21380ec 100644
--- a/libcxx/docs/ReleaseNotes/21.rst
+++ b/libcxx/docs/ReleaseNotes/21.rst
@@ -51,6 +51,7 @@ Implemented Papers
- P2441R2: ``views::join_with`` (`Github <https://github.com/llvm/llvm-project/issues/105185>`__)
- P2711R1: Making multi-param constructors of ``views`` ``explicit`` (`Github <https://github.com/llvm/llvm-project/issues/105252>`__)
- P2770R0: Stashing stashing ``iterators`` for proper flattening (`Github <https://github.com/llvm/llvm-project/issues/105250>`__)
+- P3060R2: Add ``std::views::indices(n)``
Improvements and New Features
-----------------------------
diff --git a/libcxx/include/__ranges/iota_view.h b/libcxx/include/__ranges/iota_view.h
index 4b84585258b91..c477fadce31f2 100644
--- a/libcxx/include/__ranges/iota_view.h
+++ b/libcxx/include/__ranges/iota_view.h
@@ -392,6 +392,16 @@ 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) {
+ return ranges::views::iota(decltype(__size){}, __size);
+};
+
+# endif
+
} // namespace views
} // namespace ranges
diff --git a/libcxx/include/ranges b/libcxx/include/ranges
index 2a6321bd2c5d8..aab708e63e279 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-difference-type = // exposition only
diff --git a/libcxx/include/version b/libcxx/include/version
index 91fe48351e161..f46018cdbce13 100644
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -203,6 +203,7 @@ __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>
@@ -586,6 +587,7 @@ __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/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 4cf5178dd7b8f..ce6d9ee82e66e 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 e546719142231..67f98ef933ab3 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
@@ -656,6 +656,10 @@
# 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
@@ -1588,6 +1592,10 @@
# 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
@@ -2691,6 +2699,10 @@
# 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
@@ -4061,6 +4073,10 @@
# 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
@@ -5626,6 +5642,10 @@
# 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
@@ -7536,6 +7556,13 @@
# 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/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..3d4b2bbbb89f9
--- /dev/null
+++ b/libcxx/test/std/ranges/range.factories/range.iota.view/indices.pass.cpp
@@ -0,0 +1,110 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 IntegerTypesTest {
+ template <class T>
+ constexpr void operator()() {
+ static_assert(HasIndices<T>);
+ }
+};
+
+struct NotIntegerLike {};
+
+void test_SFIANE() {
+ static_assert(HasIndices<std::size_t>);
+ types::for_each(types::integer_types(), IntegerTypesTest{});
+
+ // Not 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);
+ assert(indices_view.size() == 5);
+
+ // Check that the view is a range
+ static_assert(std::ranges::range<decltype(indices_view)>);
+
+ 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));
+ assert(indices_view.size() == 5);
+
+ // Check that the view is a range
+ static_assert(std::ranges::range<decltype(indices_view)>);
+
+ 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{});
+
+ // Check that the indices view works as expected
+ auto indices_view = std::ranges::views::indices(std::ranges::size(v));
+ assert(indices_view.size() == 5);
+
+ // Check that the view is a range
+ static_assert(std::ranges::range<decltype(indices_view)>);
+
+ 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_SFIANE();
+
+ 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 edd7b124a1fb3..df85619605f4a 100644
--- a/libcxx/utils/generate_feature_test_macro_components.py
+++ b/libcxx/utils/generate_feature_test_macro_components.py
@@ -1106,6 +1106,11 @@ 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},
``````````
</details>
https://github.com/llvm/llvm-project/pull/146823
More information about the libcxx-commits
mailing list