[libcxx-commits] [libcxx] 569d663 - [libc++] Implement ranges::equal

Nikolas Klauser via libcxx-commits libcxx-commits at lists.llvm.org
Thu May 26 01:47:44 PDT 2022


Author: Nikolas Klauser
Date: 2022-05-26T10:46:54+02:00
New Revision: 569d6630204d5146aee7c0f40872cf529181d9ef

URL: https://github.com/llvm/llvm-project/commit/569d6630204d5146aee7c0f40872cf529181d9ef
DIFF: https://github.com/llvm/llvm-project/commit/569d6630204d5146aee7c0f40872cf529181d9ef.diff

LOG: [libc++] Implement ranges::equal

Reviewed By: var-const, #libc

Spies: libcxx-commits, mgorny

Differential Revision: https://reviews.llvm.org/D123681

Added: 
    libcxx/include/__algorithm/ranges_equal.h
    libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/ranges.equal.pass.cpp

Modified: 
    libcxx/docs/Status/RangesAlgorithms.csv
    libcxx/include/CMakeLists.txt
    libcxx/include/algorithm
    libcxx/include/module.modulemap
    libcxx/test/libcxx/algorithms/ranges_robust_against_copying_comparators.pass.cpp
    libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp
    libcxx/test/libcxx/private_headers.verify.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/docs/Status/RangesAlgorithms.csv b/libcxx/docs/Status/RangesAlgorithms.csv
index 1a5989db42bf2..c757abd2201d2 100644
--- a/libcxx/docs/Status/RangesAlgorithms.csv
+++ b/libcxx/docs/Status/RangesAlgorithms.csv
@@ -8,7 +8,7 @@ Search,find_if_not,Nikolas Klauser,`D121248 <https://reviews.llvm.org/D121248>`_
 Search,find_first_of,Not assigned,n/a,Not started
 Search,adjacent_find,Not assigned,n/a,Not started
 Search,mismatch,Nikolas Klauser,`D117817 <https://llvm.org/D117817>`_,✅
-Search,equal,Not assigned,n/a,Not started
+Search,equal,Nikolas Klauser,n/a,✅
 Search,lexicographical_compare,Not assigned,n/a,Not started
 Search,partition_point,Christopher Di Bella,`D105794 <https://llvm.org/D105794>`_,Under review
 Search,lower_bound,Christopher Di Bella,`D105795 <https://llvm.org/D105795>`_,Under review

diff  --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 68482bf716f1f..65261da125865 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -72,6 +72,7 @@ set(files
   __algorithm/ranges_copy_n.h
   __algorithm/ranges_count.h
   __algorithm/ranges_count_if.h
+  __algorithm/ranges_equal.h
   __algorithm/ranges_fill.h
   __algorithm/ranges_fill_n.h
   __algorithm/ranges_find.h

diff  --git a/libcxx/include/__algorithm/ranges_equal.h b/libcxx/include/__algorithm/ranges_equal.h
new file mode 100644
index 0000000000000..c5f2d23322165
--- /dev/null
+++ b/libcxx/include/__algorithm/ranges_equal.h
@@ -0,0 +1,115 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_EQUAL_H
+#define _LIBCPP___ALGORITHM_RANGES_EQUAL_H
+
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/invoke.h>
+#include <__functional/ranges_operations.h>
+#include <__iterator/concepts.h>
+#include <__iterator/distance.h>
+#include <__iterator/indirectly_comparable.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.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 {
+namespace __equal {
+struct __fn {
+private:
+  template <class _Iter1, class _Sent1,
+            class _Iter2, class _Sent2,
+            class _Pred,
+            class _Proj1,
+            class _Proj2>
+  _LIBCPP_HIDE_FROM_ABI constexpr static
+  bool __equal_impl(_Iter1 __first1, _Sent1 __last1,
+                    _Iter2 __first2, _Sent2 __last2,
+                    _Pred& __pred,
+                    _Proj1& __proj1,
+                    _Proj2& __proj2) {
+    while (__first1 != __last1 && __first2 != __last2) {
+      if (!std::invoke(__pred, std::invoke(__proj1, *__first1), std::invoke(__proj2, *__first2)))
+        return false;
+      ++__first1;
+      ++__first2;
+    }
+    return __first1 == __last1 && __first2 == __last2;
+  }
+
+public:
+
+  template <input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
+            input_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
+            class _Pred = ranges::equal_to,
+            class _Proj1 = identity,
+            class _Proj2 = identity>
+    requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  bool operator()(_Iter1 __first1, _Sent1 __last1,
+                  _Iter2 __first2, _Sent2 __last2,
+                  _Pred __pred = {},
+                  _Proj1 __proj1 = {},
+                  _Proj2 __proj2 = {}) const {
+    if constexpr (sized_sentinel_for<_Sent1, _Iter1> && sized_sentinel_for<_Sent2, _Iter2>) {
+      if (__last1 - __first1 != __last2 - __first2)
+        return false;
+    }
+    return __equal_impl(std::move(__first1), std::move(__last1),
+                        std::move(__first2), std::move(__last2),
+                        __pred,
+                        __proj1,
+                        __proj2);
+  }
+
+  template <input_range _Range1,
+            input_range _Range2,
+            class _Pred = ranges::equal_to,
+            class _Proj1 = identity,
+            class _Proj2 = identity>
+    requires indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>, _Pred, _Proj1, _Proj2>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  bool operator()(_Range1&& __range1,
+                  _Range2&& __range2,
+                  _Pred __pred = {},
+                  _Proj1 __proj1 = {},
+                  _Proj2 __proj2 = {}) const {
+    if constexpr (sized_range<_Range1> && sized_range<_Range2>) {
+      if (ranges::distance(__range1) != ranges::distance(__range2))
+        return false;
+    }
+    return __equal_impl(ranges::begin(__range1), ranges::end(__range1),
+                        ranges::begin(__range2), ranges::end(__range2),
+                        __pred,
+                        __proj1,
+                        __proj2);
+    return false;
+  }
+};
+} // namespace __equal
+
+inline namespace __cpo {
+  inline constexpr auto equal = __equal::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+#endif // _LIBCPP___ALGORITHM_RANGES_EQUAL_H

diff  --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index ba8ac23e4bddc..aa2191464a830 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -291,6 +291,20 @@ namespace ranges {
 
   template<class T, output_iterator<const T&> O>
     constexpr O ranges::fill_n(O first, iter_
diff erence_t<O> n, const T& value);            // since C++20
+
+ template<input_iterator I1, sentinel_for<I1> S1, input_iterator I2, sentinel_for<I2> S2,
+          class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
+   requires indirectly_comparable<I1, I2, Pred, Proj1, Proj2>
+   constexpr bool ranges::equal(I1 first1, S1 last1, I2 first2, S2 last2,
+                                Pred pred = {},
+                                Proj1 proj1 = {}, Proj2 proj2 = {});                        // since C++20
+
+ template<input_range R1, input_range R2, class Pred = ranges::equal_to,
+          class Proj1 = identity, class Proj2 = identity>
+   requires indirectly_comparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
+   constexpr bool ranges::equal(R1&& r1, R2&& r2, Pred pred = {},
+                                Proj1 proj1 = {}, Proj2 proj2 = {});                        // since C++20
+
 }
 
     constexpr bool     // constexpr in C++20
@@ -1013,6 +1027,7 @@ template <class BidirectionalIterator, class Compare>
 #include <__algorithm/ranges_copy_n.h>
 #include <__algorithm/ranges_count.h>
 #include <__algorithm/ranges_count_if.h>
+#include <__algorithm/ranges_equal.h>
 #include <__algorithm/ranges_fill.h>
 #include <__algorithm/ranges_fill_n.h>
 #include <__algorithm/ranges_find.h>

diff  --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
index d3a4b45c4d96d..cf394de39a2d0 100644
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -304,6 +304,7 @@ module std [system] {
       module ranges_copy_n            { private header "__algorithm/ranges_copy_n.h" }
       module ranges_count             { private header "__algorithm/ranges_count.h" }
       module ranges_count_if          { private header "__algorithm/ranges_count_if.h" }
+      module ranges_equal             { private header "__algorithm/ranges_equal.h" }
       module ranges_fill              { private header "__algorithm/ranges_fill.h" }
       module ranges_fill_n            { private header "__algorithm/ranges_fill_n.h" }
       module ranges_find              { private header "__algorithm/ranges_find.h" }

diff  --git a/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_comparators.pass.cpp b/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_comparators.pass.cpp
index c6a8f00359219..d5b7dd11f710e 100644
--- a/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_comparators.pass.cpp
+++ b/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_comparators.pass.cpp
@@ -106,8 +106,8 @@ constexpr bool all_the_algorithms()
 #if TEST_STD_VER > 20
     //(void)std::ranges::ends_with(first, last, first2, last2, Equal(&copies)); assert(copies == 0);
 #endif
-    //(void)std::ranges::equal(first, last, first2, last2, Equal(&copies)); assert(copies == 0);
-    //(void)std::ranges::equal(a, b, Equal(&copies)); assert(copies == 0);
+    (void)std::ranges::equal(first, last, first2, last2, Equal(&copies)); assert(copies == 0);
+    (void)std::ranges::equal(a, b, Equal(&copies)); assert(copies == 0);
     //(void)std::ranges::equal_range(first, last, value, Less(&copies)); assert(copies == 0);
     //(void)std::ranges::equal_range(a, value, Less(&copies)); assert(copies == 0);
     //(void)std::ranges::find_end(first, last, first2, mid2, Equal(&copies)); assert(copies == 0);

diff  --git a/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp b/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp
index ffb4faef12b52..8d6753d562082 100644
--- a/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp
+++ b/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp
@@ -90,8 +90,8 @@ constexpr bool all_the_algorithms()
 #if TEST_STD_VER > 20
     //(void)std::ranges::ends_with(first, last, first2, last2, Equal(), Proj(&copies), Proj(&copies)); assert(copies == 0);
 #endif
-    //(void)std::ranges::equal(first, last, first2, last2, Equal(), Proj(&copies), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::equal(a, b, Equal(), Proj(&copies), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::equal(first, last, first2, last2, Equal(), Proj(&copies), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::equal(a, b, Equal(), Proj(&copies), Proj(&copies)); assert(copies == 0);
     //(void)std::ranges::equal_range(first, last, value, Less(), Proj(&copies)); assert(copies == 0);
     //(void)std::ranges::equal_range(a, value, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::find(first, last, value, Proj(&copies)); assert(copies == 0);

diff  --git a/libcxx/test/libcxx/private_headers.verify.cpp b/libcxx/test/libcxx/private_headers.verify.cpp
index 16186899f3810..b83308c7b8ead 100644
--- a/libcxx/test/libcxx/private_headers.verify.cpp
+++ b/libcxx/test/libcxx/private_headers.verify.cpp
@@ -109,6 +109,7 @@ END-SCRIPT
 #include <__algorithm/ranges_copy_n.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_copy_n.h'}}
 #include <__algorithm/ranges_count.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_count.h'}}
 #include <__algorithm/ranges_count_if.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_count_if.h'}}
+#include <__algorithm/ranges_equal.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_equal.h'}}
 #include <__algorithm/ranges_fill.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_fill.h'}}
 #include <__algorithm/ranges_fill_n.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_fill_n.h'}}
 #include <__algorithm/ranges_find.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_find.h'}}

diff  --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/ranges.equal.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/ranges.equal.pass.cpp
new file mode 100644
index 0000000000000..c7becd880a441
--- /dev/null
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/ranges.equal.pass.cpp
@@ -0,0 +1,375 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-has-no-incomplete-ranges
+
+// template<input_iterator I1, sentinel_for<I1> S1, input_iterator I2, sentinel_for<I2> S2,
+//          class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
+//   requires indirectly_comparable<I1, I2, Pred, Proj1, Proj2>
+//   constexpr bool ranges::equal(I1 first1, S1 last1, I2 first2, S2 last2,
+//                                Pred pred = {},
+//                                Proj1 proj1 = {}, Proj2 proj2 = {});
+// template<input_range R1, input_range R2, class Pred = ranges::equal_to,
+//          class Proj1 = identity, class Proj2 = identity>
+//   requires indirectly_comparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
+//   constexpr bool ranges::equal(R1&& r1, R2&& r2, Pred pred = {},
+//                                Proj1 proj1 = {}, Proj2 proj2 = {});
+
+#include <algorithm>
+#include <cassert>
+#include <concepts>
+#include <functional>
+#include <ranges>
+
+#include "almost_satisfies_types.h"
+#include "test_iterators.h"
+
+template <class Iter1, class Sent1 = sentinel_wrapper<Iter1>,
+          class Iter2 = Iter1, class Sent2 = sentinel_wrapper<Iter2>>
+concept HasEqualIt = requires (Iter1 first1, Sent1 last1, Iter2 first2, Sent2 last2) {
+  std::ranges::equal(first1, last1, first2, last2);
+};
+
+static_assert(HasEqualIt<int*>);
+static_assert(!HasEqualIt<InputIteratorNotDerivedFrom>);
+static_assert(!HasEqualIt<InputIteratorNotIndirectlyReadable>);
+static_assert(!HasEqualIt<InputIteratorNotInputOrOutputIterator>);
+static_assert(!HasEqualIt<int*, int*, InputIteratorNotDerivedFrom>);
+static_assert(!HasEqualIt<int*, int*, InputIteratorNotIndirectlyReadable>);
+static_assert(!HasEqualIt<int*, int*, InputIteratorNotInputOrOutputIterator>);
+static_assert(!HasEqualIt<int*, SentinelForNotSemiregular>);
+static_assert(!HasEqualIt<int*, SentinelForNotWeaklyEqualityComparableWith>);
+static_assert(!HasEqualIt<int*, int*, int*, SentinelForNotSemiregular>);
+static_assert(!HasEqualIt<int*, int*, int*, SentinelForNotWeaklyEqualityComparableWith>);
+static_assert(!HasEqualIt<int*, int*, int**>);
+
+template <class Range1, class Range2>
+concept HasEqualR = requires (Range1 range1, Range2 range2) {
+  std::ranges::equal(range1, range2);
+};
+
+static_assert(HasEqualR<UncheckedRange<int*>, UncheckedRange<int*>>);
+static_assert(!HasEqualR<InputRangeNotDerivedFrom, UncheckedRange<int*>>);
+static_assert(!HasEqualR<InputRangeNotIndirectlyReadable, UncheckedRange<int*>>);
+static_assert(!HasEqualR<InputRangeNotInputOrOutputIterator, UncheckedRange<int*>>);
+static_assert(!HasEqualR<InputRangeNotSentinelSemiregular, UncheckedRange<int*>>);
+static_assert(!HasEqualR<InputRangeNotSentinelEqualityComparableWith, UncheckedRange<int*>>);
+static_assert(!HasEqualR<UncheckedRange<int*>, InputRangeNotDerivedFrom>);
+static_assert(!HasEqualR<UncheckedRange<int*>, InputRangeNotIndirectlyReadable>);
+static_assert(!HasEqualR<UncheckedRange<int*>, InputRangeNotInputOrOutputIterator>);
+static_assert(!HasEqualR<UncheckedRange<int*>, InputRangeNotSentinelSemiregular>);
+static_assert(!HasEqualR<UncheckedRange<int*>, InputRangeNotSentinelEqualityComparableWith>);
+static_assert(!HasEqualR<UncheckedRange<int*>, UncheckedRange<int**>>);
+
+template <class Iter1, class Sent1, class Iter2, class Sent2 = Iter2>
+constexpr void test_iterators() {
+  { // simple test
+    {
+      int a[] = {1, 2, 3, 4};
+      int b[] = {1, 2, 3, 4};
+      std::same_as<bool> decltype(auto) ret = std::ranges::equal(Iter1(a), Sent1(Iter1(a + 4)),
+                                                                 Iter2(b), Sent2(Iter2(b + 4)));
+      assert(ret);
+    }
+    {
+      int a[] = {1, 2, 3, 4};
+      int b[] = {1, 2, 3, 4};
+      auto range1 = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 4)));
+      auto range2 = std::ranges::subrange(Iter2(b), Sent2(Iter2(b + 4)));
+      std::same_as<bool> decltype(auto) ret = std::ranges::equal(range1, range2);
+      assert(ret);
+    }
+  }
+
+  { // check that the predicate is used (return true)
+    {
+      int a[] = {1, 2, 3, 4};
+      int b[] = {2, 3, 4, 5};
+      auto ret = std::ranges::equal(Iter1(a), Sent1(Iter1(a + 4)), Iter2(b), Sent2(Iter2(b + 4)),
+                                    [](int l, int r) { return l != r; });
+      assert(ret);
+    }
+    {
+      int a[] = {1, 2, 3, 4};
+      int b[] = {2, 3, 4, 5};
+      auto range1 = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 4)));
+      auto range2 = std::ranges::subrange(Iter2(b), Sent2(Iter2(b + 4)));
+      auto ret = std::ranges::equal(range1, range2, [](int l, int r) { return l != r; });
+      assert(ret);
+    }
+  }
+
+  { // check that the predicate is used (return false)
+    {
+      int a[] = {1, 2, 3, 4};
+      int b[] = {2, 3, 3, 5};
+      auto ret = std::ranges::equal(Iter1(a), Sent1(Iter1(a + 4)), Iter2(b), Sent2(Iter2(b + 4)),
+                                    [](int l, int r) { return l != r; });
+      assert(!ret);
+    }
+    {
+      int a[] = {1, 2, 3, 4};
+      int b[] = {2, 3, 3, 5};
+      auto range1 = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 4)));
+      auto range2 = std::ranges::subrange(Iter2(b), Sent2(Iter2(b + 4)));
+      auto ret = std::ranges::equal(range1, range2, [](int l, int r) { return l != r; });
+      assert(!ret);
+    }
+  }
+
+  { // check that the projections are used
+    {
+      int a[] = {1, 2, 3, 4, 5};
+      int b[] = {6, 10, 14, 18, 22};
+      auto ret = std::ranges::equal(Iter1(a), Sent1(Iter1(a + 5)),
+                                    Iter2(b), Sent2(Iter2(b + 5)),
+                                    {},
+                                    [](int i) { return i * 4; },
+                                    [](int i) { return i - 2; });
+      assert(ret);
+    }
+    {
+      int a[] = {1, 2, 3, 4, 5};
+      int b[] = {6, 10, 14, 18, 22};
+      auto range1 = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 5)));
+      auto range2 = std::ranges::subrange(Iter2(b), Sent2(Iter2(b + 5)));
+      auto ret = std::ranges::equal(range1,
+                                    range2,
+                                    {},
+                                    [](int i) { return i * 4; },
+                                    [](int i) { return i - 2; });
+      assert(ret);
+    }
+  }
+
+  { // check that 
diff erent sized ranges work
+    {
+      int a[] = {4, 3, 2, 1};
+      int b[] = {4, 3, 2, 1, 5, 6, 7};
+      auto ret = std::ranges::equal(Iter1(a), Sent1(Iter1(a + 4)), Iter2(b), Sent2(Iter2(b + 7)));
+      assert(!ret);
+    }
+    {
+      int a[] = {4, 3, 2, 1};
+      int b[] = {4, 3, 2, 1, 5, 6, 7};
+      auto range1 = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 4)));
+      auto range2 = std::ranges::subrange(Iter2(b), Sent2(Iter2(b + 7)));
+      auto ret = std::ranges::equal(range1, range2);
+      assert(!ret);
+    }
+  }
+
+  { // check that two ranges with the same size but 
diff erent values are 
diff erent
+    {
+      int a[] = {4, 6, 34, 76, 5};
+      int b[] = {4, 6, 34, 67, 5};
+      auto ret = std::ranges::equal(Iter1(a), Sent1(Iter1(a + 5)), Iter2(b), Sent2(Iter2(b + 5)));
+      assert(!ret);
+    }
+    {
+      int a[] = {4, 6, 34, 76, 5};
+      int b[] = {4, 6, 34, 67, 5};
+      auto range1 = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 5)));
+      auto range2 = std::ranges::subrange(Iter2(b), Sent2(Iter2(b + 5)));
+      auto ret = std::ranges::equal(range1, range2);
+      assert(!ret);
+    }
+  }
+
+  { // check that two empty ranges work
+    {
+      int a[] = {};
+      int b[] = {};
+      auto ret = std::ranges::equal(Iter1(a), Sent1(Iter1(a)), Iter2(b), Sent2(Iter2(b)));
+      assert(ret);
+    }
+    {
+      int a[] = {};
+      int b[] = {};
+      auto range1 = std::ranges::subrange(Iter1(a), Sent1(Iter1(a)));
+      auto range2 = std::ranges::subrange(Iter2(b), Sent2(Iter2(b)));
+      auto ret = std::ranges::equal(range1, range2);
+      assert(ret);
+    }
+  }
+
+  { // check that it works with the first range empty
+    {
+      int a[] = {};
+      int b[] = {1, 2};
+      auto ret = std::ranges::equal(Iter1(a), Sent1(Iter1(a)), Iter2(b), Sent2(Iter2(b + 2)));
+      assert(!ret);
+    }
+    {
+      int a[] = {};
+      int b[] = {1, 2};
+      auto range1 = std::ranges::subrange(Iter1(a), Sent1(Iter1(a)));
+      auto range2 = std::ranges::subrange(Iter2(b), Sent2(Iter2(b + 2)));
+      auto ret = std::ranges::equal(range1, range2);
+      assert(!ret);
+    }
+  }
+
+  { // check that it works with the second range empty
+    {
+      int a[] = {1, 2};
+      int b[] = {};
+      auto ret = std::ranges::equal(Iter1(a), Sent1(Iter1(a + 2)), Iter2(b), Sent2(Iter2(b)));
+      assert(!ret);
+    }
+    {
+      int a[] = {1, 2};
+      int b[] = {};
+      auto range1 = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 2)));
+      auto range2 = std::ranges::subrange(Iter2(b), Sent2(Iter2(b)));
+      auto ret = std::ranges::equal(range1, range2);
+      assert(!ret);
+    }
+  }
+}
+
+template<class Iter1, class Sent1 = Iter1>
+constexpr void test_iterators2() {
+  test_iterators<Iter1, Sent1, cpp17_input_iterator<int*>, sentinel_wrapper<cpp17_input_iterator<int*>>>();
+  test_iterators<Iter1, Sent1, cpp20_input_iterator<int*>, sentinel_wrapper<cpp20_input_iterator<int*>>>();
+  test_iterators<Iter1, Sent1, forward_iterator<int*>>();
+  test_iterators<Iter1, Sent1, bidirectional_iterator<int*>>();
+  test_iterators<Iter1, Sent1, random_access_iterator<int*>>();
+  test_iterators<Iter1, Sent1, contiguous_iterator<int*>>();
+  test_iterators<Iter1, Sent1, int*>();
+  test_iterators<Iter1, Sent1, const int*>();
+}
+
+constexpr bool test() {
+  test_iterators2<cpp17_input_iterator<int*>, sentinel_wrapper<cpp17_input_iterator<int*>>>();
+  test_iterators2<cpp20_input_iterator<int*>, sentinel_wrapper<cpp20_input_iterator<int*>>>();
+  test_iterators2<forward_iterator<int*>>();
+  test_iterators2<bidirectional_iterator<int*>>();
+  test_iterators2<random_access_iterator<int*>>();
+  test_iterators2<contiguous_iterator<int*>>();
+  test_iterators2<int*>();
+  test_iterators2<const int*>();
+
+  { // check that std::invoke is used
+    struct S {
+      constexpr S(int i_) : i(i_) {}
+      constexpr bool equal(int o) { return i == o; }
+      constexpr S& identity() { return *this; }
+      int i;
+    };
+    {
+      S a[] = {7, 8, 9};
+      S b[] = {7, 8, 9};
+      auto ret = std::ranges::equal(a, a + 3, b, b + 3, &S::equal, &S::identity, &S::i);
+      assert(ret);
+    }
+    {
+      S a[] = {7, 8, 9};
+      S b[] = {7, 8, 9};
+      auto ret = std::ranges::equal(a, b, &S::equal, &S::identity, &S::i);
+      assert(ret);
+    }
+  }
+
+  { // check that the complexity requirements are met
+    { // 
diff erent size
+      {
+        int a[] = {1, 2, 3};
+        int b[] = {1, 2, 3, 4};
+        int predCount = 0;
+        int projCount = 0;
+        auto pred = [&](int l, int r) { ++predCount; return l == r; };
+        auto proj = [&](int i) { ++projCount; return i; };
+        auto ret = std::ranges::equal(a, a + 3, b, b + 4, pred, proj, proj);
+        assert(!ret);
+        assert(predCount == 0);
+        assert(projCount == 0);
+      }
+      {
+        int a[] = {1, 2, 3};
+        int b[] = {1, 2, 3, 4};
+        int predCount = 0;
+        int projCount = 0;
+        auto pred = [&](int l, int r) { ++predCount; return l == r; };
+        auto proj = [&](int i) { ++projCount; return i; };
+        auto ret = std::ranges::equal(a, b, pred, proj, proj);
+        assert(!ret);
+        assert(predCount == 0);
+        assert(projCount == 0);
+      }
+    }
+
+    { // not a sized sentinel
+      {
+        int a[] = {1, 2, 3};
+        int b[] = {1, 2, 3, 4};
+        int predCount = 0;
+        int projCount = 0;
+        auto pred = [&](int l, int r) { ++predCount; return l == r; };
+        auto proj = [&](int i) { ++projCount; return i; };
+        auto ret = std::ranges::equal(a, sentinel_wrapper(a + 3), b, sentinel_wrapper(b + 4), pred, proj, proj);
+        assert(!ret);
+        assert(predCount <= 4);
+        assert(projCount <= 7);
+      }
+      {
+        int a[] = {1, 2, 3};
+        int b[] = {1, 2, 3, 4};
+        int predCount = 0;
+        int projCount = 0;
+        auto pred = [&](int l, int r) { ++predCount; return l == r; };
+        auto proj = [&](int i) { ++projCount; return i; };
+        auto range1 = std::ranges::subrange(a, sentinel_wrapper(a + 3));
+        auto range2 = std::ranges::subrange(b, sentinel_wrapper(b + 4));
+        auto ret = std::ranges::equal(range1, range2, pred, proj, proj);
+        assert(!ret);
+        assert(predCount <= 4);
+        assert(projCount <= 7);
+      }
+    }
+
+    { // same size
+      {
+        int a[] = {1, 2, 3};
+        int b[] = {1, 2, 3};
+        int predCount = 0;
+        int projCount = 0;
+        auto pred = [&](int l, int r) { ++predCount; return l == r; };
+        auto proj = [&](int i) { ++projCount; return i; };
+        auto ret = std::ranges::equal(a, a + 3, b, b + 3, pred, proj, proj);
+        assert(ret);
+        assert(predCount == 3);
+        assert(projCount == 6);
+      }
+      {
+        int a[] = {1, 2, 3};
+        int b[] = {1, 2, 3};
+        int predCount = 0;
+        int projCount = 0;
+        auto pred = [&](int l, int r) { ++predCount; return l == r; };
+        auto proj = [&](int i) { ++projCount; return i; };
+        auto ret = std::ranges::equal(a, b, pred, proj, proj);
+        assert(ret);
+        assert(predCount == 3);
+        assert(projCount == 6);
+      }
+    }
+  }
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}


        


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