[libc++][C++23] P2440R1: Implement ranges::iota

[PaulXiCao]

The paper P2440 introduces three groups of functions: std::ranges::iota, std::ranges::shift_left, and std::ranges::shift_right.

This mr implements std::ranges::iota. For reference:

• https://en.cppreference.com/w/cpp/algorithm/ranges/iota
• https://eel.is/c++draft/numeric.iota.

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff c28e268c32a6840d08e3a4dbc9eeb8a0f564d6c0 40a283071edad4fcfbe1f7d80accf6c48f76061a --extensions ,cpp,h -- libcxx/include/__algorithm/out_value_result.h libcxx/test/std/algorithms/algorithms.results/out_value_result.pass.cpp libcxx/test/std/numerics/numeric.ops/numeric.iota/ranges_iota.pass.cpp libcxx/include/__numeric/iota.h libcxx/include/algorithm libcxx/include/numeric libcxx/include/version libcxx/test/std/language.support/support.limits/support.limits.general/numeric.version.compile.pass.cpp libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp

View the diff from clang-format here.

diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 9058541824..d2fadd0b1e 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -2024,11 +2024,11 @@ template <class BidirectionalIterator, class Compare>
 
 #if _LIBCPP_STD_VER >= 23
 #  include <__algorithm/fold.h>
+#  include <__algorithm/out_value_result.h>
 #  include <__algorithm/ranges_contains_subrange.h>
 #  include <__algorithm/ranges_ends_with.h>
 #  include <__algorithm/ranges_find_last.h>
 #  include <__algorithm/ranges_starts_with.h>
-#  include <__algorithm/out_value_result.h>
 #endif // _LIBCPP_STD_VER >= 23
 
 #include <version>
diff --git a/libcxx/test/std/algorithms/algorithms.results/out_value_result.pass.cpp b/libcxx/test/std/algorithms/algorithms.results/out_value_result.pass.cpp
index fa04acf4be..b7b813a0a3 100644
--- a/libcxx/test/std/algorithms/algorithms.results/out_value_result.pass.cpp
+++ b/libcxx/test/std/algorithms/algorithms.results/out_value_result.pass.cpp
@@ -30,8 +30,10 @@ struct B {
 // implicit conversion
 static_assert(std::is_constructible_v<std::ranges::out_value_result<B, B>, std::ranges::out_value_result<int, int>>);
 static_assert(std::is_constructible_v<std::ranges::out_value_result<B, B>, std::ranges::out_value_result<int, int>&>);
-static_assert(std::is_constructible_v<std::ranges::out_value_result<B, B>, const std::ranges::out_value_result<int, int>>);
-static_assert(std::is_constructible_v<std::ranges::out_value_result<B, B>, const std::ranges::out_value_result<int, int>&>);
+static_assert(
+    std::is_constructible_v<std::ranges::out_value_result<B, B>, const std::ranges::out_value_result<int, int>>);
+static_assert(
+    std::is_constructible_v<std::ranges::out_value_result<B, B>, const std::ranges::out_value_result<int, int>&>);
 
 struct C {
   C(int&);
@@ -39,10 +41,14 @@ struct C {
 static_assert(!std::is_constructible_v<std::ranges::out_value_result<C, C>, std::ranges::out_value_result<int, int>&>);
 
 // has to be convertible via const&
-static_assert(std::is_convertible_v<std::ranges::out_value_result<int, int>&, std::ranges::out_value_result<long, long>>);
-static_assert(std::is_convertible_v<const std::ranges::out_value_result<int, int>&, std::ranges::out_value_result<long, long>>);
-static_assert(std::is_convertible_v<std::ranges::out_value_result<int, int>&&, std::ranges::out_value_result<long, long>>);
-static_assert(std::is_convertible_v<const std::ranges::out_value_result<int, int>&&, std::ranges::out_value_result<long, long>>);
+static_assert(
+    std::is_convertible_v<std::ranges::out_value_result<int, int>&, std::ranges::out_value_result<long, long>>);
+static_assert(
+    std::is_convertible_v<const std::ranges::out_value_result<int, int>&, std::ranges::out_value_result<long, long>>);
+static_assert(
+    std::is_convertible_v<std::ranges::out_value_result<int, int>&&, std::ranges::out_value_result<long, long>>);
+static_assert(
+    std::is_convertible_v<const std::ranges::out_value_result<int, int>&&, std::ranges::out_value_result<long, long>>);
 
 // should be move constructible
 static_assert(std::is_move_constructible_v<std::ranges::out_value_result<MoveOnly, int>>);
@@ -54,8 +60,10 @@ static_assert(!std::is_copy_constructible_v<std::ranges::out_value_result<int, M
 
 struct NotConvertible {};
 // conversions should not work if there is no conversion
-static_assert(!std::is_convertible_v<std::ranges::out_value_result<NotConvertible, int>, std::ranges::out_value_result<int, int>>);
-static_assert(!std::is_convertible_v<std::ranges::out_value_result<int, NotConvertible>, std::ranges::out_value_result<int, int>>);
+static_assert(!std::is_convertible_v<std::ranges::out_value_result<NotConvertible, int>,
+                                     std::ranges::out_value_result<int, int>>);
+static_assert(!std::is_convertible_v<std::ranges::out_value_result<int, NotConvertible>,
+                                     std::ranges::out_value_result<int, int>>);
 
 template <class T>
 struct ConvertibleFrom {

[Zingam]

@PaulXiCao I think there is already an active PR implementing ranges::iota #68494
also another one implementing ranges::shift_left: #83231

We have now a project libc++ Standard Conformance libc++ Standards Conformance (view)

I believe noone is working on cartesian_product but you should ask on Discord first.

[PaulXiCao]

@Zingam Thanks for the feedback! I will close this pr and see if I can give any valueable feedback in the mentioned prs.

The linked "libc++ Standard Conformance" project seems really useful!