[libc++] Implement ranges::equal

Reviewed By: var-const, #libc

Spies: libcxx-commits, mgorny

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

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

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

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

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_difference_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>

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" }

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);

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);

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'}}