[libc++] Implement ranges::ends_with

Reviewed By: #libc, var-const

Differential Revision: https://reviews.llvm.org/D150831

libcxx/benchmarks/CMakeLists.txt

@@ -172,6 +172,7 @@ set(BENCHMARK_TESTS
     algorithms/pop_heap.bench.cpp
     algorithms/pstl.stable_sort.bench.cpp
     algorithms/push_heap.bench.cpp
+    algorithms/ranges_ends_with.bench.cpp
     algorithms/ranges_make_heap.bench.cpp
     algorithms/ranges_make_heap_then_sort_heap.bench.cpp
     algorithms/ranges_pop_heap.bench.cpp

libcxx/benchmarks/algorithms/ranges_ends_with.bench.cpp

@@ -0,0 +1,107 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <algorithm>
+#include <benchmark/benchmark.h>
+#include <iterator>
+
+#include "test_iterators.h"
+#include <vector>
+
+static void bm_ends_with_contiguous_iter(benchmark::State& state) {
+  std::vector<int> a(state.range(), 1);
+  std::vector<int> p(state.range(), 1);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(a);
+    benchmark::DoNotOptimize(p);
+
+    auto begin1 = contiguous_iterator(a.data());
+    auto end1   = contiguous_iterator(a.data() + a.size());
+    auto begin2 = contiguous_iterator(p.data());
+    auto end2   = contiguous_iterator(p.data() + p.size());
+
+    benchmark::DoNotOptimize(std::ranges::ends_with(begin1, end1, begin2, end2));
+  }
+}
+BENCHMARK(bm_ends_with_contiguous_iter)->RangeMultiplier(16)->Range(16, 16 << 20);
+
+static void bm_ends_with_random_iter(benchmark::State& state) {
+  std::vector<int> a(state.range(), 1);
+  std::vector<int> p(state.range(), 1);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(a);
+    benchmark::DoNotOptimize(p);
+
+    auto begin1 = random_access_iterator(a.begin());
+    auto end1   = random_access_iterator(a.end());
+    auto begin2 = random_access_iterator(p.begin());
+    auto end2   = random_access_iterator(p.end());
+
+    benchmark::DoNotOptimize(std::ranges::ends_with(begin1, end1, begin2, end2));
+  }
+}
+BENCHMARK(bm_ends_with_random_iter)->RangeMultiplier(16)->Range(16, 16 << 20);
+
+static void bm_ends_with_bidirectional_iter(benchmark::State& state) {
+  std::vector<int> a(state.range(), 1);
+  std::vector<int> p(state.range(), 1);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(a);
+    benchmark::DoNotOptimize(p);
+
+    auto begin1 = bidirectional_iterator(a.begin());
+    auto end1   = bidirectional_iterator(a.end());
+    auto begin2 = bidirectional_iterator(p.begin());
+    auto end2   = bidirectional_iterator(p.end());
+
+    benchmark::DoNotOptimize(std::ranges::ends_with(begin1, end1, begin2, end2));
+  }
+}
+BENCHMARK(bm_ends_with_bidirectional_iter)->RangeMultiplier(16)->Range(16, 16 << 20);
+
+static void bm_ends_with_forward_iter(benchmark::State& state) {
+  std::vector<int> a(state.range(), 1);
+  std::vector<int> p(state.range(), 1);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(a);
+    benchmark::DoNotOptimize(p);
+
+    auto begin1 = forward_iterator(a.begin());
+    auto end1   = forward_iterator(a.end());
+    auto begin2 = forward_iterator(p.begin());
+    auto end2   = forward_iterator(p.end());
+
+    benchmark::DoNotOptimize(std::ranges::ends_with(begin1, end1, begin2, end2));
+  }
+}
+BENCHMARK(bm_ends_with_forward_iter)->RangeMultiplier(16)->Range(16, 16 << 20);
+
+static void bm_ends_with_forward_iter_with_size_optimization(benchmark::State& state) {
+  std::vector<int> a(state.range(), 1);
+  std::vector<int> p(state.range(), 1);
+  p.push_back(2);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(a);
+    benchmark::DoNotOptimize(p);
+
+    auto begin1 = forward_iterator(a.begin());
+    auto end1   = forward_iterator(a.end());
+    auto begin2 = forward_iterator(p.begin());
+    auto end2   = forward_iterator(p.end());
+
+    benchmark::DoNotOptimize(std::ranges::ends_with(begin1, end1, begin2, end2));
+  }
+}
+BENCHMARK(bm_ends_with_forward_iter_with_size_optimization)->RangeMultiplier(16)->Range(16, 16 << 20);
+
+BENCHMARK_MAIN();

libcxx/include/CMakeLists.txt

@@ -110,6 +110,7 @@ set(files
   __algorithm/ranges_copy_n.h
   __algorithm/ranges_count.h
   __algorithm/ranges_count_if.h
+  __algorithm/ranges_ends_with.h
   __algorithm/ranges_equal.h
   __algorithm/ranges_equal_range.h
   __algorithm/ranges_fill.h

libcxx/include/__algorithm/ranges_ends_with.h

@@ -0,0 +1,196 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_ENDS_WITH_H
+#define _LIBCPP___ALGORITHM_RANGES_ENDS_WITH_H
+
+#include <__algorithm/ranges_equal.h>
+#include <__algorithm/ranges_starts_with.h>
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/ranges_operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__iterator/advance.h>
+#include <__iterator/concepts.h>
+#include <__iterator/distance.h>
+#include <__iterator/indirectly_comparable.h>
+#include <__iterator/reverse_iterator.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 >= 23
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+namespace __ends_with {
+struct __fn {
+  template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class _Pred, class _Proj1, class _Proj2>
+  static _LIBCPP_HIDE_FROM_ABI constexpr bool __ends_with_fn_impl_bidirectional(
+      _Iter1 __first1,
+      _Sent1 __last1,
+      _Iter2 __first2,
+      _Sent2 __last2,
+      _Pred& __pred,
+      _Proj1& __proj1,
+      _Proj2& __proj2) {
+    auto __rbegin1 = std::make_reverse_iterator(__last1);
+    auto __rend1   = std::make_reverse_iterator(__first1);
+    auto __rbegin2 = std::make_reverse_iterator(__last2);
+    auto __rend2   = std::make_reverse_iterator(__first2);
+    return ranges::starts_with(
+        __rbegin1, __rend1, __rbegin2, __rend2, std::ref(__pred), std::ref(__proj1), std::ref(__proj2));
+  }
+
+  template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class _Pred, class _Proj1, class _Proj2>
+  static _LIBCPP_HIDE_FROM_ABI constexpr bool __ends_with_fn_impl(
+      _Iter1 __first1,
+      _Sent1 __last1,
+      _Iter2 __first2,
+      _Sent2 __last2,
+      _Pred& __pred,
+      _Proj1& __proj1,
+      _Proj2& __proj2) {
+    if constexpr (std::bidirectional_iterator<_Sent1> && std::bidirectional_iterator<_Sent2> &&
+                  (!std::random_access_iterator<_Sent1>)&&(!std::random_access_iterator<_Sent2>)) {
+      return __ends_with_fn_impl_bidirectional(__first1, __last1, __first2, __last2, __pred, __proj1, __proj2);
+
+    } else {
+      auto __n1 = ranges::distance(__first1, __last1);
+      auto __n2 = ranges::distance(__first2, __last2);
+      if (__n2 == 0)
+        return true;
+      if (__n2 > __n1)
+        return false;
+
+      return __ends_with_fn_impl_with_offset(
+          std::move(__first1),
+          std::move(__last1),
+          std::move(__first2),
+          std::move(__last2),
+          __pred,
+          __proj1,
+          __proj2,
+          __n1 - __n2);
+    }
+  }
+
+  template <class _Iter1,
+            class _Sent1,
+            class _Iter2,
+            class _Sent2,
+            class _Pred,
+            class _Proj1,
+            class _Proj2,
+            class _Offset>
+  static _LIBCPP_HIDE_FROM_ABI constexpr bool __ends_with_fn_impl_with_offset(
+      _Iter1 __first1,
+      _Sent1 __last1,
+      _Iter2 __first2,
+      _Sent2 __last2,
+      _Pred& __pred,
+      _Proj1& __proj1,
+      _Proj2& __proj2,
+      _Offset __offset) {
+    if constexpr (std::bidirectional_iterator<_Sent1> && std::bidirectional_iterator<_Sent2> &&
+                  !std::random_access_iterator<_Sent1> && !std::random_access_iterator<_Sent2>) {
+      return __ends_with_fn_impl_bidirectional(
+          std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), __pred, __proj1, __proj2);
+
+    } else {
+      ranges::advance(__first1, __offset);
+      return ranges::equal(
+          std::move(__first1),
+          std::move(__last1),
+          std::move(__first2),
+          std::move(__last2),
+          std::ref(__pred),
+          std::ref(__proj1),
+          std::ref(__proj2));
+    }
+  }
+
+  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(forward_iterator<_Iter1> || sized_sentinel_for<_Sent1, _Iter1>) &&
+            (forward_iterator<_Iter2> || sized_sentinel_for<_Sent2, _Iter2>) &&
+            indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(
+      _Iter1 __first1,
+      _Sent1 __last1,
+      _Iter2 __first2,
+      _Sent2 __last2,
+      _Pred __pred   = {},
+      _Proj1 __proj1 = {},
+      _Proj2 __proj2 = {}) const {
+    return __ends_with_fn_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(forward_range<_Range1> || sized_range<_Range1>) && (forward_range<_Range2> || sized_range<_Range2>) &&
+            indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>, _Pred, _Proj1, _Proj2>
+  _LIBCPP_NODISCARD_EXT _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>) {
+      auto __n1 = ranges::size(__range1);
+      auto __n2 = ranges::size(__range2);
+      if (__n2 == 0)
+        return true;
+      if (__n2 > __n1)
+        return false;
+      auto __offset = __n1 - __n2;
+
+      return __ends_with_fn_impl_with_offset(
+          ranges::begin(__range1),
+          ranges::end(__range1),
+          ranges::begin(__range2),
+          ranges::end(__range2),
+          __pred,
+          __proj1,
+          __proj2,
+          __offset);
+
+    } else {
+      return __ends_with_fn_impl(
+          ranges::begin(__range1),
+          ranges::end(__range1),
+          ranges::begin(__range2),
+          ranges::end(__range2),
+          __pred,
+          __proj1,
+          __proj2);
+    }
+  }
+};
+} // namespace __ends_with
+
+inline namespace __cpo {
+inline constexpr auto ends_with = __ends_with::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER >= 23
+
+#endif // _LIBCPP___ALGORITHM_RANGES_ENDS_WITH_H

libcxx/include/algorithm

@@ -447,6 +447,22 @@ namespace ranges {
            indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred>
     constexpr bool ranges::any_of(R&& r, Pred pred, Proj proj = {});                        // 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 (forward_iterator<I1> || sized_sentinel_for<S1, I1>) &&
+           (forward_iterator<I2> || sized_sentinel_for<S2, I2>) &&
+           indirectly_comparable<I1, I2, Pred, Proj1, Proj2>
+    constexpr bool ranges::ends_with(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
+                                   Proj1 proj1 = {}, Proj2 proj2 = {});                     // since C++23
+
+  template<input_range R1, input_range R2, class Pred = ranges::equal_to, class Proj1 = identity,
+          class Proj2 = identity>
+    requires (forward_range<R1> || sized_range<R1>) &&
+           (forward_range<R2> || sized_range<R2>) &&
+           indirectly_comparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
+    constexpr bool ranges::ends_with(R1&& r1, R2&& r2, Pred pred = {},
+                                   Proj1 proj1 = {}, Proj2 proj2 = {});                     // since C++23
+
   template<input_iterator I, sentinel_for<I> S, class Proj = identity,
            indirect_unary_predicate<projected<I, Proj>> Pred>
     constexpr bool ranges::none_of(I first, S last, Pred pred, Proj proj = {});             // since C++20
@@ -1833,6 +1849,7 @@ 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_ends_with.h>
 #include <__algorithm/ranges_equal.h>
 #include <__algorithm/ranges_equal_range.h>
 #include <__algorithm/ranges_fill.h>

libcxx/modules/std/algorithm.inc

@@ -154,10 +154,10 @@ export namespace std {
     // [alg.starts.with], starts with
     using std::ranges::starts_with;
 
-#  if 0
     // [alg.ends.with], ends with
     using std::ranges::ends_with;
 
+#  if 0
     // [alg.fold], fold
     using std::ranges::fold_left;
     using std::ranges::fold_left_first;

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

@@ -102,8 +102,9 @@ constexpr bool all_the_algorithms()
     (void)std::ranges::count_if(a, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::copy_if(first, last, first2, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::copy_if(a, first2, UnaryTrue(&copies)); assert(copies == 0);
-#if TEST_STD_VER > 20
-    //(void)std::ranges::ends_with(first, last, first2, last2, Equal(&copies)); assert(copies == 0);
+#if TEST_STD_VER >= 23
+    (void)std::ranges::ends_with(first, last, first2, last2, Equal(&copies)); assert(copies == 0);
+    (void)std::ranges::ends_with(a, b, 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);

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

@@ -86,8 +86,9 @@ constexpr bool all_the_algorithms()
     (void)std::ranges::count_if(a, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::copy_if(first, last, first2, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::copy_if(a, first2, UnaryTrue(), Proj(&copies)); assert(copies == 0);
-#if TEST_STD_VER > 20
-    //(void)std::ranges::ends_with(first, last, first2, last2, Equal(), Proj(&copies), Proj(&copies)); assert(copies == 0);
+#if TEST_STD_VER >= 23
+    (void)std::ranges::ends_with(first, last, first2, last2, Equal(), Proj(&copies), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::ends_with(a, b, 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);

libcxx/test/std/algorithms/alg.nonmodifying/alg.ends_with/ranges.ends_with.pass.cpp

@@ -0,0 +1,275 @@
+//===----------------------------------------------------------------------===//
+//
+// 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, 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::ends_with(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::ends_with(R1&& r1, R2&& r2, Pred pred = {},
+//                                      Proj1 proj1 = {}, Proj2 proj2 = {});
+
+#include <algorithm>
+#include <array>
+#include <chrono>
+#include <ranges>
+#include "almost_satisfies_types.h"
+#include "test_iterators.h"
+
+using namespace std::chrono;
+
+template <class Iter1, class Sent1 = Iter1, class Iter2 = int*, class Sent2 = Iter2>
+concept HasEndsWithIt = requires(Iter1 first1, Sent1 last1, Iter2 first2, Sent2 last2) {
+  std::ranges::ends_with(first1, last1, first2, last2);
+};
+
+static_assert(HasEndsWithIt<int*>);
+static_assert(!HasEndsWithIt<ForwardIteratorNotDerivedFrom>);
+static_assert(!HasEndsWithIt<ForwardIteratorNotIncrementable>);
+static_assert(HasEndsWithIt<int*, int*>);
+static_assert(!HasEndsWithIt<int*, SentinelForNotSemiregular>);
+static_assert(!HasEndsWithIt<int*, int*, int**>); // not indirectly comparable
+static_assert(!HasEndsWithIt<int*, SentinelForNotWeaklyEqualityComparableWith>);
+static_assert(!HasEndsWithIt<int*, int*, ForwardIteratorNotDerivedFrom>);
+static_assert(!HasEndsWithIt<int*, int*, ForwardIteratorNotIncrementable>);
+static_assert(!HasEndsWithIt<int*, int*, int*, SentinelForNotSemiregular>);
+static_assert(!HasEndsWithIt<int*, int*, int*, SentinelForNotWeaklyEqualityComparableWith>);
+
+template <class Range1, class Range2 = UncheckedRange<int*>>
+concept HasEndsWithR = requires(Range1&& range1, Range2&& range2) {
+    std::ranges::ends_with(std::forward<Range1>(range1), std::forward<Range2>(range2)); };
+
+static_assert(HasEndsWithR<UncheckedRange<int*>>);
+static_assert(!HasEndsWithR<ForwardRangeNotDerivedFrom>);
+static_assert(!HasEndsWithR<ForwardIteratorNotIncrementable>);
+static_assert(!HasEndsWithR<ForwardRangeNotSentinelSemiregular>);
+static_assert(!HasEndsWithR<ForwardRangeNotSentinelEqualityComparableWith>);
+static_assert(HasEndsWithR<UncheckedRange<int*>, UncheckedRange<int*>>);
+static_assert(!HasEndsWithR<UncheckedRange<int*>, UncheckedRange<int**>>); // not indirectly comparable
+static_assert(!HasEndsWithR<UncheckedRange<int*>, ForwardRangeNotDerivedFrom>);
+static_assert(!HasEndsWithR<UncheckedRange<int*>, ForwardRangeNotSentinelSemiregular>);
+
+// clang-format off
+template <class Iter1, class Sent1 = Iter1, class Iter2, class Sent2 = Iter2>
+constexpr void test_iterators() {
+  { // simple tests
+    int a[]          = {1, 2, 3, 4, 5, 6};
+    int p[]          = {4, 5, 6};
+    auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
+    auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 3)));
+    {
+      [[maybe_unused]] std::same_as<bool> decltype(auto) ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+      assert(ret);
+    }
+    {
+      [[maybe_unused]] std::same_as<bool> decltype(auto) ret = std::ranges::ends_with(whole, suffix);
+      assert(ret);
+    }
+  }
+
+  { // suffix doesn't match
+    int a[] = {1, 2, 3, 4, 5, 6};
+    int p[] = {1, 2, 3};
+    auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
+    auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 3)));
+    {
+      bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+      assert(!ret);
+    }
+    {
+      bool ret = std::ranges::ends_with(whole, suffix);
+      assert(!ret);
+    }
+  }
+
+  { // range consists of just one element
+    int a[] = {1};
+    int p[] = {1};
+    auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 1)));
+    auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 1)));
+    {
+      bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+      assert(ret);
+    }
+    {
+      bool ret = std::ranges::ends_with(whole, suffix);
+      assert(ret);
+    }
+  }
+
+  { // suffix consists of just one element
+    int a[] = {5, 1, 2, 4, 3};
+    int p[] = {3};
+    auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 5)));
+    auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 1)));
+    {
+      bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+      assert(ret);
+    }
+    {
+      bool ret = std::ranges::ends_with(whole, suffix);
+      assert(ret);
+    }
+  }
+
+  { // range and suffix are identical
+    int a[] = {1, 2, 3, 4, 5, 6};
+    int p[] = {1, 2, 3, 4, 5, 6};
+    auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
+    auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 6)));
+    {
+      bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+      assert(ret);
+    }
+    {
+      bool ret = std::ranges::ends_with(whole, suffix);
+      assert(ret);
+    }
+  }
+
+  { // suffix is longer than range
+    int a[] = {3, 4, 5, 6, 7, 8};
+    int p[] = {1, 2, 3, 4, 5, 6, 7, 8};
+    auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
+    auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 8)));
+    {
+      bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+      assert(!ret);
+    }
+    {
+      bool ret = std::ranges::ends_with(whole, suffix);
+      assert(!ret);
+    }
+ }
+
+ { // suffix has zero length
+   int a[] = {1, 2, 3, 4, 5, 6};
+   int p[] = {};
+   auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
+   auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p)));
+   {
+     bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+     assert(ret);
+   }
+   {
+     bool ret = std::ranges::ends_with(whole, suffix);
+     assert(ret);
+   }
+ }
+
+ { // range has zero length
+   int a[] = {};
+   int p[] = {1, 2, 3, 4, 5, 6, 7, 8};
+   auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a)));
+   auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 8)));
+   {
+     bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+     assert(!ret);
+   }
+   {
+     bool ret = std::ranges::ends_with(whole, suffix);
+     assert(!ret);
+   }
+ }
+
+ { // subarray
+   int a[] = {0, 3, 5, 10, 7, 3, 5, 89, 3, 5, 2, 1, 8, 6};
+   int p[] = {3, 5};
+   auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 13)));
+   auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 2)));
+   {
+     bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+     assert(!ret);
+   }
+   {
+     bool ret = std::ranges::ends_with(whole, suffix);
+     assert(!ret);
+   }
+ }
+
+ { // repeated suffix
+   int a[] = {8, 6, 3, 5, 1, 2};
+   int p[] = {1, 2, 1, 2};
+   auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
+   auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 4)));
+   {
+     bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end());
+     assert(!ret);
+   }
+   {
+     bool ret = std::ranges::ends_with(whole, suffix);
+     assert(!ret);
+   }
+ }
+
+ { // check that the predicate is used
+   int a[] = {5, 1, 3, 2, 7};
+   int p[] = {-2, -7};
+   auto pred = [](int l, int r) { return l * -1 == r; };
+   auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 5)));
+   auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 2)));
+   {
+     bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end(), pred);
+     assert(ret);
+   }
+   {
+     bool ret = std::ranges::ends_with(whole, suffix, pred);
+     assert(ret);
+   }
+ }
+
+ { // check that the projections are used
+   int a[] = {1, 3, 15, 1, 2, 1};
+   int p[] = {2, 1, 2};
+   auto whole = std::ranges::subrange(Iter1(a), Sent1(Iter1(a + 6)));
+   auto suffix  = std::ranges::subrange(Iter2(p), Sent2(Iter2(p + 3)));
+   {
+     bool ret = std::ranges::ends_with(whole.begin(), whole.end(), suffix.begin(), suffix.end(), {},
+         [](int i) { return i - 3; },
+         [](int i) { return i * -1; });
+     assert(ret);
+   }
+   {
+     bool ret = std::ranges::ends_with(whole, suffix, {},
+         [](int i) { return i - 3; },
+         [](int i) { return i * -1; });
+     assert(ret);
+   }
+  }
+}
+
+constexpr bool test() {
+  // This is to test (forward_iterator<_Iter1> || sized_sentinel_for<_Sent1, _Iter1>) condition.
+  types::for_each(types::cpp20_input_iterator_list<int*>{}, []<class Iter2>() {
+    types::for_each(types::cpp20_input_iterator_list<int*>{}, []<class Iter1>() {
+      if constexpr (std::forward_iterator<Iter1> && std::forward_iterator<Iter2>)
+        test_iterators<Iter1, Iter1, Iter2, Iter2>();
+      if constexpr (std::forward_iterator<Iter2>)
+        test_iterators<Iter1, sized_sentinel<Iter1>, Iter2, Iter2>();
+      if constexpr (std::forward_iterator<Iter1>)
+        test_iterators<Iter1, Iter1, Iter2, sized_sentinel<Iter2>>();
+      test_iterators<Iter1, sized_sentinel<Iter1>, Iter2, sized_sentinel<Iter2>>();
+    });
+  });
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/algorithms/ranges_robust_against_differing_projections.pass.cpp

@@ -54,6 +54,9 @@ constexpr bool test_all() {
   auto proj1 = [](int x) { return x * -1; };
   auto proj2 = [](A a) { return a.x * -1; };
 
+#if TEST_STD_VER >= 23
+  test(std::ranges::ends_with, in, in2, eq, proj1, proj2);
+#endif
   test(std::ranges::equal, in, in2, eq, proj1, proj2);
   test(std::ranges::lexicographical_compare, in, in2, eq, proj1, proj2);
   test(std::ranges::is_permutation, in, in2, eq, proj1, proj2);
@@ -77,7 +80,6 @@ constexpr bool test_all() {
   test(std::ranges::set_union, in, in2, out2, less, proj1, proj2);
 #if TEST_STD_VER > 20
   test(std::ranges::starts_with, in, in2, eq, proj1, proj2);
-  // test(std::ranges::ends_with, in, in2, eq, proj1, proj2);
 #endif
 
   return true;

libcxx/test/std/algorithms/ranges_robust_against_nonbool_predicates.pass.cpp

@@ -22,6 +22,7 @@
 #include <ranges>
 
 #include "boolean_testable.h"
+#include "test_macros.h"
 
 constexpr auto unary_pred = [](int i) { return BooleanTestable(i > 0); };
 static_assert(!std::same_as<decltype(unary_pred(1)), bool>);
@@ -68,6 +69,9 @@ constexpr bool test_all() {
 
   test(std::ranges::any_of, in, unary_pred);
   test(std::ranges::all_of, in, unary_pred);
+#if TEST_STD_VER >= 23
+  test(std::ranges::ends_with, in, in2, binary_pred);
+#endif
   test(std::ranges::none_of, in, unary_pred);
   test(std::ranges::find_if, in, unary_pred);
   test(std::ranges::find_if_not, in, unary_pred);
@@ -118,6 +122,9 @@ constexpr bool test_all() {
   test(std::ranges::partition_copy, in, out, out2, unary_pred);
   test(std::ranges::partial_sort_copy, in, in2, binary_pred);
   test(std::ranges::merge, in, in2, out, binary_pred);
+#if TEST_STD_VER > 20
+  test(std::ranges::starts_with, in, in2, binary_pred);
+#endif
   test(std::ranges::set_difference, in, in2, out, binary_pred);
   test(std::ranges::set_intersection, in, in2, out, binary_pred);
   test(std::ranges::set_symmetric_difference, in, in2, out, binary_pred);

libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp

@@ -19,6 +19,7 @@
 #include <initializer_list>
 #include <iterator>
 #include <ranges>
+#include "test_macros.h"
 
 struct Foo {
   int val;
@@ -73,6 +74,9 @@ constexpr bool test_all() {
 
   test(std::ranges::any_of, in, &Foo::unary_pred, &Bar::val);
   test(std::ranges::all_of, in, &Foo::unary_pred, &Bar::val);
+#if TEST_STD_VER >= 23
+  test(std::ranges::ends_with, in, in2, &Foo::binary_pred, &Bar::val, &Bar::val);
+#endif
   test(std::ranges::none_of, in, &Foo::unary_pred, &Bar::val);
   test(std::ranges::find, in, x, &Bar::val);
   test(std::ranges::find_if, in, &Foo::unary_pred, &Bar::val);
@@ -143,6 +147,9 @@ constexpr bool test_all() {
   test(std::ranges::partition_copy, in, out, out2, &Foo::unary_pred, &Bar::val);
   test(std::ranges::partial_sort_copy, in, in2, &Foo::binary_pred, &Bar::val, &Bar::val);
   test(std::ranges::merge, in, in2, out, &Foo::binary_pred, &Bar::val, &Bar::val);
+#if TEST_STD_VER > 20
+  test(std::ranges::starts_with, in, in2, &Foo::binary_pred, &Bar::val, &Bar::val);
+#endif
   test(std::ranges::set_difference, in, in2, out, &Foo::binary_pred, &Bar::val, &Bar::val);
   test(std::ranges::set_intersection, in, in2, out, &Foo::binary_pred, &Bar::val, &Bar::val);
   test(std::ranges::set_symmetric_difference, in, in2, out, &Foo::binary_pred, &Bar::val, &Bar::val);

libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp

@@ -25,6 +25,7 @@
 
 #include "MoveOnly.h"
 #include "test_iterators.h"
+#include "test_macros.h"
 
 // (in, ...)
 template <class Func, std::ranges::range Input, class ...Args>
@@ -73,6 +74,9 @@ constexpr void run_tests() {
 
   test(std::ranges::any_of, in, unary_pred);
   test(std::ranges::all_of, in, unary_pred);
+#if TEST_STD_VER >= 23
+  test(std::ranges::ends_with, in, in2);
+#endif
   test(std::ranges::none_of, in, unary_pred);
   test(std::ranges::find, in, x);
   test(std::ranges::find_if, in, unary_pred);
@@ -129,6 +133,9 @@ constexpr void run_tests() {
     test(std::ranges::replace_copy, in, out, x, x);
     test(std::ranges::replace_copy_if, in, out, unary_pred, x);
   }
+#if TEST_STD_VER > 20
+  test(std::ranges::starts_with, in, in2);
+#endif
   test(std::ranges::swap_ranges, in, in2);
   if constexpr (std::copyable<T>) {
     test(std::ranges::reverse_copy, in, out);

libcxx/test/std/library/description/conventions/customization.point.object/niebloid.compile.pass.cpp

@@ -71,7 +71,9 @@ static_assert(test(std::ranges::copy_if, a, a, odd));
 static_assert(test(std::ranges::copy_n, a, 10, a));
 static_assert(test(std::ranges::count, a, 42));
 static_assert(test(std::ranges::count_if, a, odd));
-//static_assert(test(std::ranges::ends_with, a, a));
+#if TEST_STD_VER >= 23
+static_assert(test(std::ranges::ends_with, a, a));
+#endif
 static_assert(test(std::ranges::equal, a, a));
 static_assert(test(std::ranges::equal_range, a, 42));
 static_assert(test(std::ranges::fill, a, 42));