[libc++][ranges] implement std::ranges::set_intersection

implement `std::ranges::set_intersection` by reusing the classic `std::set_intersenction`
added unit tests

Differential Revision: https://reviews.llvm.org/D129233

libcxx/docs/Status/RangesAlgorithms.csv

@@ -62,7 +62,7 @@ Write,partition_copy,Not assigned,n/a,Not started
 Write,partial_sort_copy,Not assigned,n/a,Not started
 Merge,merge,Hui Xie,`D128611 <https://llvm.org/D128611>`_,✅
 Merge,set_difference,Hui Xie,`D128983 <https://llvm.org/D128983>`,✅
-Merge,set_intersection,Hui Xie,n/a,Not started
+Merge,set_intersection,Hui Xie,`D129233 <https://llvm.org/D129233>`,✅
 Merge,set_symmetric_difference,Hui Xie,n/a,Not started
 Merge,set_union,Hui Xie,n/a,Not started
 Permutation,remove,Nikolas Klauser,`D128618 <https://llvm.org/D128618>`_,✅

libcxx/include/CMakeLists.txt

@@ -113,6 +113,7 @@ set(files
   __algorithm/ranges_replace_if.h
   __algorithm/ranges_reverse.h
   __algorithm/ranges_set_difference.h
+  __algorithm/ranges_set_intersection.h
   __algorithm/ranges_sort.h
   __algorithm/ranges_sort_heap.h
   __algorithm/ranges_stable_sort.h

libcxx/include/__algorithm/iterator_operations.h

@@ -13,6 +13,7 @@
 #include <__iterator/advance.h>
 #include <__iterator/distance.h>
 #include <__iterator/iterator_traits.h>
+#include <__iterator/next.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -24,6 +25,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 struct _RangesIterOps {
   static constexpr auto advance = ranges::advance;
   static constexpr auto distance = ranges::distance;
+  static constexpr auto next = ranges::next;
 };
 #endif
 
@@ -40,6 +42,12 @@ struct _StdIterOps {
     return std::distance(__first, __last);
   }
 
+  template <class _Iterator>
+  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR_AFTER_CXX11
+  _Iterator next(_Iterator, _Iterator __last) {
+    return __last;
+  }
+
 };
 
 _LIBCPP_END_NAMESPACE_STD

libcxx/include/__algorithm/ranges_set_intersection.h

@@ -0,0 +1,117 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___ALGORITHM_RANGES_SET_INTERSECTION_H
+#define _LIBCPP___ALGORITHM_RANGES_SET_INTERSECTION_H
+
+#include <__algorithm/in_in_out_result.h>
+#include <__algorithm/iterator_operations.h>
+#include <__algorithm/make_projected.h>
+#include <__algorithm/set_intersection.h>
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/invoke.h>
+#include <__functional/ranges_operations.h>
+#include <__iterator/concepts.h>
+#include <__iterator/mergeable.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__ranges/dangling.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+
+template <class _InIter1, class _InIter2, class _OutIter>
+using set_intersection_result = in_in_out_result<_InIter1, _InIter2, _OutIter>;
+
+namespace __set_intersection {
+
+struct __fn {
+  template <
+      input_iterator _InIter1,
+      sentinel_for<_InIter1> _Sent1,
+      input_iterator _InIter2,
+      sentinel_for<_InIter2> _Sent2,
+      weakly_incrementable _OutIter,
+      class _Comp  = less,
+      class _Proj1 = identity,
+      class _Proj2 = identity>
+    requires mergeable<_InIter1, _InIter2, _OutIter, _Comp, _Proj1, _Proj2>
+  _LIBCPP_HIDE_FROM_ABI constexpr set_intersection_result<_InIter1, _InIter2, _OutIter> operator()(
+      _InIter1 __first1,
+      _Sent1 __last1,
+      _InIter2 __first2,
+      _Sent2 __last2,
+      _OutIter __result,
+      _Comp __comp   = {},
+      _Proj1 __proj1 = {},
+      _Proj2 __proj2 = {}) const {
+    auto __ret = std::__set_intersection<_RangesIterOps>(
+        std::move(__first1),
+        std::move(__last1),
+        std::move(__first2),
+        std::move(__last2),
+        std::move(__result),
+        ranges::__make_projected_comp(__comp, __proj1, __proj2));
+    return {std::move(__ret.in1), std::move(__ret.in2), std::move(__ret.out)};
+  }
+
+  template <
+      input_range _Range1,
+      input_range _Range2,
+      weakly_incrementable _OutIter,
+      class _Comp  = less,
+      class _Proj1 = identity,
+      class _Proj2 = identity>
+    requires mergeable<
+        iterator_t<_Range1>,
+        iterator_t<_Range2>,
+        _OutIter,
+        _Comp,
+        _Proj1,
+        _Proj2> 
+    _LIBCPP_HIDE_FROM_ABI constexpr set_intersection_result<borrowed_iterator_t<_Range1>,
+                                                            borrowed_iterator_t<_Range2>,
+                                                            _OutIter>
+    operator()(
+        _Range1&& __range1,
+        _Range2&& __range2,
+        _OutIter __result,
+        _Comp __comp   = {},
+        _Proj1 __proj1 = {},
+        _Proj2 __proj2 = {}) const {
+    auto __ret = std::__set_intersection<_RangesIterOps>(
+        ranges::begin(__range1),
+        ranges::end(__range1),
+        ranges::begin(__range2),
+        ranges::end(__range2),
+        std::move(__result),
+        ranges::__make_projected_comp(__comp, __proj1, __proj2));
+    return {std::move(__ret.in1), std::move(__ret.in2), std::move(__ret.out)};
+  }
+};
+
+} // namespace __set_intersection
+
+inline namespace __cpo {
+  inline constexpr auto set_intersection = __set_intersection::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+#endif // _LIBCPP___ALGORITHM_RANGES_SET_INTERSECTION_H

libcxx/include/__algorithm/set_intersection.h

@@ -11,57 +11,87 @@
 
 #include <__algorithm/comp.h>
 #include <__algorithm/comp_ref_type.h>
+#include <__algorithm/iterator_operations.h>
 #include <__config>
 #include <__iterator/iterator_traits.h>
+#include <__utility/move.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
-_LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator
-__set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
-                   _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
-{
-    while (__first1 != __last1 && __first2 != __last2)
-    {
-        if (__comp(*__first1, *__first2))
-            ++__first1;
-        else
-        {
-            if (!__comp(*__first2, *__first1))
-            {
-                *__result = *__first1;
-                ++__result;
-                ++__first1;
-            }
-            ++__first2;
-        }
+template <class _InIter1, class _InIter2, class _OutIter>
+struct __set_intersection_result {
+  _InIter1 in1;
+  _InIter2 in2;
+  _OutIter out;
+
+  // need a constructor as C++03 aggregate init is hard
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17
+  __set_intersection_result(_InIter1&& __inIter1, _InIter2&& __inIter2, _OutIter&& __outIter)
+      : in1(std::move(__inIter1)), in2(std::move(__inIter2)), out(std::move(__outIter)) {}
+};
+
+template < class _IterOper, class _Compare, class _InIter1, class _Sent1, class _InIter2, class _Sent2, class _OutIter>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 __set_intersection_result<_InIter1, _InIter2, _OutIter>
+__set_intersection(
+    _InIter1 __first1, _Sent1 __last1, _InIter2 __first2, _Sent2 __last2, _OutIter __result, _Compare&& __comp) {
+  while (__first1 != __last1 && __first2 != __last2) {
+    if (__comp(*__first1, *__first2))
+      ++__first1;
+    else {
+      if (!__comp(*__first2, *__first1)) {
+        *__result = *__first1;
+        ++__result;
+        ++__first1;
+      }
+      ++__first2;
     }
-    return __result;
+  }
+
+  return __set_intersection_result<_InIter1, _InIter2, _OutIter>(
+      _IterOper::next(std::move(__first1), std::move(__last1)),
+      _IterOper::next(std::move(__first2), std::move(__last2)),
+      std::move(__result));
 }
 
 template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-_OutputIterator
-set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
-                 _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
-{
-    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
-    return _VSTD::__set_intersection<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator set_intersection(
+    _InputIterator1 __first1,
+    _InputIterator1 __last1,
+    _InputIterator2 __first2,
+    _InputIterator2 __last2,
+    _OutputIterator __result,
+    _Compare __comp) {
+  typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
+  return std::__set_intersection<_StdIterOps, _Comp_ref>(
+             std::move(__first1),
+             std::move(__last1),
+             std::move(__first2),
+             std::move(__last2),
+             std::move(__result),
+             __comp)
+      .out;
 }
 
 template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-_OutputIterator
-set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
-                 _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
-{
-    return _VSTD::set_intersection(__first1, __last1, __first2, __last2, __result,
-                                  __less<typename iterator_traits<_InputIterator1>::value_type,
-                                         typename iterator_traits<_InputIterator2>::value_type>());
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator set_intersection(
+    _InputIterator1 __first1,
+    _InputIterator1 __last1,
+    _InputIterator2 __first2,
+    _InputIterator2 __last2,
+    _OutputIterator __result) {
+  return std::__set_intersection<_StdIterOps>(
+             std::move(__first1),
+             std::move(__last1),
+             std::move(__first2),
+             std::move(__last2),
+             std::move(__result),
+             __less<typename iterator_traits<_InputIterator1>::value_type,
+                    typename iterator_traits<_InputIterator2>::value_type>())
+      .out;
 }
 
 _LIBCPP_END_NAMESPACE_STD

libcxx/include/algorithm

@@ -604,6 +604,25 @@ namespace ranges {
       set_difference(R1&& r1, R2&& r2, O result,
                      Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});                           // since C++20
 
+  template<class I1, class I2, class O>
+    using set_intersection_result = in_in_out_result<I1, I2, O>;                                    // since C++20
+
+  template<input_iterator I1, sentinel_for<I1> S1, input_iterator I2, sentinel_for<I2> S2,
+           weakly_incrementable O, class Comp = ranges::less,
+           class Proj1 = identity, class Proj2 = identity>
+    requires mergeable<I1, I2, O, Comp, Proj1, Proj2>
+    constexpr set_intersection_result<I1, I2, O>
+      set_intersection(I1 first1, S1 last1, I2 first2, S2 last2, O result,
+                       Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});                         // since C++20
+
+  template<input_iterator I1, sentinel_for<I1> S1, input_iterator I2, sentinel_for<I2> S2,
+           weakly_incrementable O, class Comp = ranges::less,
+           class Proj1 = identity, class Proj2 = identity>
+    requires mergeable<I1, I2, O, Comp, Proj1, Proj2>
+    constexpr set_intersection_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>, O>
+      set_intersection(R1&& r1, R2&& r2, O result,
+                       Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});                         // since C++20
+
 }
 
     constexpr bool     // constexpr in C++20
@@ -1378,6 +1397,7 @@ template <class BidirectionalIterator, class Compare>
 #include <__algorithm/ranges_replace_if.h>
 #include <__algorithm/ranges_reverse.h>
 #include <__algorithm/ranges_set_difference.h>
+#include <__algorithm/ranges_set_intersection.h>
 #include <__algorithm/ranges_sort.h>
 #include <__algorithm/ranges_sort_heap.h>
 #include <__algorithm/ranges_stable_sort.h>

libcxx/include/module.modulemap.in

@@ -352,6 +352,7 @@ module std [system] {
       module ranges_replace_if               { private header "__algorithm/ranges_replace_if.h" }
       module ranges_reverse                  { private header "__algorithm/ranges_reverse.h" }
       module ranges_set_difference           { private header "__algorithm/ranges_set_difference.h" }
+      module ranges_set_intersection         { private header "__algorithm/ranges_set_intersection.h" }
       module ranges_sort                     { private header "__algorithm/ranges_sort.h" }
       module ranges_sort_heap                { private header "__algorithm/ranges_sort_heap.h" }
       module ranges_stable_sort              { private header "__algorithm/ranges_stable_sort.h" }

libcxx/test/libcxx/algorithms/ranges_robust_against_copying_comparators.pass.cpp

@@ -201,8 +201,8 @@ constexpr bool all_the_algorithms()
     //(void)std::ranges::search_n(a, count, value, Equal(&copies)); assert(copies == 0);
     (void)std::ranges::set_difference(first, mid, mid, last, first2, Less(&copies)); assert(copies == 0);
     (void)std::ranges::set_difference(a, b, first2, Less(&copies)); assert(copies == 0);
-    //(void)std::ranges::set_intersection(first, mid, mid, last, first2, Less(&copies)); assert(copies == 0);
-    //(void)std::ranges::set_intersection(a, b, first2, Less(&copies)); assert(copies == 0);
+    (void)std::ranges::set_intersection(first, mid, mid, last, first2, Less(&copies)); assert(copies == 0);
+    (void)std::ranges::set_intersection(a, b, first2, Less(&copies)); assert(copies == 0);
     //(void)std::ranges::set_symmetric_difference(first, mid, mid, last, first2, Less(&copies)); assert(copies == 0);
     //(void)std::ranges::set_symmetric_difference(a, b, first2, Less(&copies)); assert(copies == 0);
     //(void)std::ranges::set_union(first, mid, mid, last, first2, Less(&copies)); assert(copies == 0);

libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp

@@ -192,8 +192,8 @@ constexpr bool all_the_algorithms()
     //(void)std::ranges::search_n(a, count, value, Equal(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::set_difference(first, mid, mid, last, first2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::set_difference(a, b, first2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::set_intersection(first, mid, mid, last, first2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::set_intersection(a, b, first2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::set_intersection(first, mid, mid, last, first2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::set_intersection(a, b, first2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
     //(void)std::ranges::set_symmetric_difference(first, mid, mid, last, first2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
     //(void)std::ranges::set_symmetric_difference(a, b, first2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
     //(void)std::ranges::set_union(first, mid, mid, last, first2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);

libcxx/test/libcxx/private_headers.verify.cpp

@@ -150,6 +150,7 @@ END-SCRIPT
 #include <__algorithm/ranges_replace_if.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_replace_if.h'}}
 #include <__algorithm/ranges_reverse.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_reverse.h'}}
 #include <__algorithm/ranges_set_difference.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_set_difference.h'}}
+#include <__algorithm/ranges_set_intersection.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_set_intersection.h'}}
 #include <__algorithm/ranges_sort.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_sort.h'}}
 #include <__algorithm/ranges_sort_heap.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_sort_heap.h'}}
 #include <__algorithm/ranges_stable_sort.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_stable_sort.h'}}

libcxx/test/std/algorithms/alg.sorting/alg.merge/ranges_merge.pass.cpp

@@ -205,27 +205,11 @@ constexpr void testImpl() {
 
   // check that ranges::dangling is returned for non-borrowed_range and iterator_t is returned for borrowed_range
   {
-    struct NonBorrowedRange {
-      int* data_;
-      size_t size_;
-
-      // TODO: std::ranges::merge calls std::ranges::copy
-      // std::ranges::copy(contiguous_iterator<int*>, sentinel_wrapper<contiguous_iterator<int*>>, contiguous_iterator<int*>) doesn't seem to work.
-      // It seems that std::ranges::copy calls std::copy, which unwraps contiguous_iterator<int*> into int*,
-      // and then it failed because there is no == between int* and sentinel_wrapper<contiguous_iterator<int*>>
-      using Sent = std::conditional_t<std::contiguous_iterator<In2>, In2, sentinel_wrapper<In2>>;
-
-      constexpr NonBorrowedRange(int* d, size_t s) : data_{d}, size_{s} {}
-
-      constexpr In2 begin() const { return In2{data_}; };
-      constexpr Sent end() const { return Sent{In2{data_ + size_}}; };
-    };
-
     std::array r1{3, 6, 7, 9};
     std::array r2{2, 3, 4};
     std::array<int, 7> out;
     std::same_as<merge_result<std::array<int, 4>::iterator, std::ranges::dangling, int*>> decltype(auto) result =
-        std::ranges::merge(r1, NonBorrowedRange{r2.data(), r2.size()}, out.data());
+        std::ranges::merge(r1, NonBorrowedRange<In2>{r2.data(), r2.size()}, out.data());
     assert(base(result.in1) == r1.end());
     assert(base(result.out) == out.data() + out.size());
     assert(std::ranges::equal(out, std::array{2, 3, 3, 4, 6, 7, 9}));