[libc++] Implement ranges::contains (#65148)

Differential Revision: https://reviews.llvm.org/D159232
```
Running ./ranges_contains.libcxx.out
Run on (10 X 24.121 MHz CPU s)
CPU Caches:
  L1 Data 64 KiB (x10)
  L1 Instruction 128 KiB (x10)
  L2 Unified 4096 KiB (x5)
Load Average: 3.37, 6.77, 5.27
--------------------------------------------------------------------
Benchmark                          Time             CPU   Iterations
--------------------------------------------------------------------
bm_contains_char/16             1.88 ns         1.87 ns    371607095
bm_contains_char/256            7.48 ns         7.47 ns     93292285
bm_contains_char/4096           99.7 ns         99.6 ns      7013185
bm_contains_char/65536          1296 ns         1294 ns       540436
bm_contains_char/1048576       23887 ns        23860 ns        29302
bm_contains_char/16777216     389420 ns       389095 ns         1796
bm_contains_int/16              7.14 ns         7.14 ns     97776288
bm_contains_int/256             90.4 ns         90.3 ns      7558089
bm_contains_int/4096            1294 ns         1290 ns       543052
bm_contains_int/65536          20482 ns        20443 ns        34334
bm_contains_int/1048576       328817 ns       327965 ns         2147
bm_contains_int/16777216     5246279 ns      5239361 ns          133
bm_contains_bool/16             2.19 ns         2.19 ns    322565780
bm_contains_bool/256            3.42 ns         3.41 ns    205025467
bm_contains_bool/4096           22.1 ns         22.1 ns     31780479
bm_contains_bool/65536           333 ns          332 ns      2106606
bm_contains_bool/1048576        5126 ns         5119 ns       135901
bm_contains_bool/16777216      81656 ns        81574 ns         8569
```

---------

Co-authored-by: Nathan Gauër <brioche@google.com>

3 files changed, 300 insertions, 0 deletions

diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
new file mode 100644
index 0000000..c928698
--- /dev/null
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
@@ -0,0 +1,298 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 I, sentinel_for<I> S, class T, class Proj = identity>
+//     requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*>
+//     constexpr bool ranges::contains(I first, S last, const T& value, Proj proj = {});       // since C++23
+
+// template<input_range R, class T, class Proj = identity>
+//     requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
+//     constexpr bool ranges::contains(R&& r, const T& value, Proj proj = {});                 // since C++23
+
+#include <algorithm>
+#include <cassert>
+#include <list>
+#include <ranges>
+#include <string>
+#include <vector>
+
+#include "almost_satisfies_types.h"
+#include "boolean_testable.h"
+#include "test_iterators.h"
+
+struct NotEqualityComparable {};
+
+template <class Iter, class Sent = Iter>
+concept HasContainsIt = requires(Iter iter, Sent sent) { std::ranges::contains(iter, sent, *iter); };
+
+static_assert(HasContainsIt<int*>);
+static_assert(HasContainsIt<int*, int*>);
+static_assert(!HasContainsIt<NotEqualityComparable*>);
+static_assert(!HasContainsIt<InputIteratorNotDerivedFrom>);
+static_assert(!HasContainsIt<InputIteratorNotIndirectlyReadable>);
+static_assert(!HasContainsIt<InputIteratorNotInputOrOutputIterator>);
+static_assert(!HasContainsIt<cpp20_input_iterator<int*>, SentinelForNotSemiregular>);
+static_assert(!HasContainsIt<cpp20_input_iterator<int*>, InputRangeNotSentinelEqualityComparableWith>);
+static_assert(!HasContainsIt<cpp20_input_iterator<int*>, sentinel_wrapper<cpp20_input_iterator<int*>>>);
+
+static_assert(!HasContainsIt<int*, int>);
+static_assert(!HasContainsIt<int, int*>);
+
+template <class Range, class ValT>
+concept HasContainsR = requires(Range&& range) { std::ranges::contains(std::forward<Range>(range), ValT{}); };
+
+static_assert(!HasContainsR<int, int>);
+static_assert(HasContainsR<int[1], int>);
+static_assert(!HasContainsR<NotEqualityComparable[1], NotEqualityComparable>);
+static_assert(!HasContainsR<InputRangeNotDerivedFrom, int>);
+static_assert(!HasContainsR<InputRangeNotIndirectlyReadable, int>);
+static_assert(!HasContainsR<InputRangeNotInputOrOutputIterator, int>);
+static_assert(!HasContainsR<InputRangeNotSentinelSemiregular, int>);
+static_assert(!HasContainsR<InputRangeNotSentinelEqualityComparableWith, int>);
+
+template <class Iter, class Sent = Iter>
+constexpr void test_iterators() {
+  using ValueT = std::iter_value_t<Iter>;
+  { // simple tests
+    ValueT a[] = {1, 2, 3, 4, 5, 6};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 6)));
+    {
+      std::same_as<bool> decltype(auto) ret = std::ranges::contains(whole.begin(), whole.end(), 3);
+      assert(ret);
+    }
+    {
+      std::same_as<bool> decltype(auto) ret = std::ranges::contains(whole, 3);
+      assert(ret);
+    }
+  }
+
+  { // check that a range with a single element works
+    ValueT a[] = {32};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 1)));
+    {
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 32);
+      assert(ret);
+    }
+    {
+      bool ret = std::ranges::contains(whole, 32);
+      assert(ret);
+    }
+  }
+
+  { // check that an empty range works
+    ValueT a[] = {};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a)));
+    {
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 1);
+      assert(!ret);
+    }
+    {
+      bool ret = std::ranges::contains(whole, 1);
+      assert(!ret);
+    }
+  }
+
+  { // check that the first element matches
+    ValueT a[] = {32, 3, 2, 1, 0, 23, 21, 9, 40, 100};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 10)));
+    {
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 32);
+      assert(ret);
+    }
+    {
+      bool ret = std::ranges::contains(whole, 32);
+      assert(ret);
+    }
+  }
+
+  { // check that the last element matches
+    ValueT a[] = {3, 22, 1, 43, 99, 0, 56, 100, 32};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 9)));
+    {
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 32);
+      assert(ret);
+    }
+    {
+      bool ret = std::ranges::contains(whole, 32);
+      assert(ret);
+    }
+  }
+
+  { // no match
+    ValueT a[] = {13, 1, 21, 4, 5};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 5)));
+    {
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 10);
+      assert(!ret);
+    }
+    {
+      bool ret = std::ranges::contains(whole, 10);
+      assert(!ret);
+    }
+  }
+
+  { // check that the projections are used
+    int a[] = {1, 9, 0, 13, 25};
+    {
+      bool ret = std::ranges::contains(a, a + 5, -13, [&](int i) { return i * -1; });
+      assert(ret);
+    }
+    {
+      auto range = std::ranges::subrange(a, a + 5);
+      bool ret   = std::ranges::contains(range, -13, [&](int i) { return i * -1; });
+      assert(ret);
+    }
+  }
+}
+
+constexpr bool test() {
+  types::for_each(types::type_list<char, long long>{}, []<class T> {
+    types::for_each(types::cpp20_input_iterator_list<T*>{}, []<class Iter> {
+      if constexpr (std::forward_iterator<Iter>)
+        test_iterators<Iter>();
+      test_iterators<Iter, sentinel_wrapper<Iter>>();
+      test_iterators<Iter, sized_sentinel<Iter>>();
+    });
+  });
+
+  { // count invocations of the projection for continuous iterators
+    int a[]              = {1, 9, 0, 13, 25};
+    int projection_count = 0;
+    {
+      bool ret = std::ranges::contains(a, a + 5, 0, [&](int i) {
+        ++projection_count;
+        return i;
+      });
+      assert(ret);
+      assert(projection_count == 3);
+      projection_count = 0;
+    }
+    {
+      bool ret = std::ranges::contains(a, 0, [&](int i) {
+        ++projection_count;
+        return i;
+      });
+      assert(ret);
+      assert(projection_count == 3);
+    }
+  }
+
+  { // check invocations of the projection for std::string
+    const std::string str{"hello world"};
+    const std::string str1{"hi world"};
+    int projection_count = 0;
+    {
+      std::string a[] = {str1, str1, str, str1, str1};
+      auto whole =
+          std::ranges::subrange(forward_iterator(std::move_iterator(a)), forward_iterator(std::move_iterator(a + 5)));
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), "hello world", [&](const std::string i) {
+        ++projection_count;
+        return i;
+      });
+      assert(ret);
+      assert(projection_count == 3);
+      projection_count = 0;
+    }
+    {
+      std::string a[] = {str1, str1, str, str1, str1};
+      auto whole =
+          std::ranges::subrange(forward_iterator(std::move_iterator(a)), forward_iterator(std::move_iterator(a + 5)));
+      bool ret = std::ranges::contains(whole, "hello world", [&](const std::string i) {
+        ++projection_count;
+        return i;
+      });
+      assert(ret);
+      assert(projection_count == 3);
+    }
+  }
+
+  { // check invocations of the projection for non-continuous iterators
+    std::vector<bool> whole{false, false, true, false};
+    int projection_count = 0;
+    {
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), true, [&](int i) {
+        ++projection_count;
+        return i;
+      });
+      assert(ret);
+      assert(projection_count == 3);
+      projection_count = 0;
+    }
+    {
+      bool ret = std::ranges::contains(whole, true, [&](int i) {
+        ++projection_count;
+        return i;
+      });
+      assert(ret);
+      assert(projection_count == 3);
+    }
+  }
+
+  { // check invocations of the projection for views::transform
+    int a[]              = {1, 2, 3, 4, 5};
+    int projection_count = 0;
+    auto square_number   = a | std::views::transform([](int x) { return x * x; });
+    {
+      bool ret = std::ranges::contains(square_number.begin(), square_number.end(), 16, [&](int i) {
+        ++projection_count;
+        return i;
+      });
+      assert(ret);
+      assert(projection_count == 4);
+      projection_count = 0;
+    }
+    {
+      bool ret = std::ranges::contains(square_number, 16, [&](int i) {
+        ++projection_count;
+        return i;
+      });
+      assert(ret);
+      assert(projection_count == 4);
+    }
+  }
+
+  return true;
+}
+
+// test for non-contiguous containers
+bool test_nonconstexpr() {
+  std::list<int> a     = {7, 5, 0, 16, 8};
+  int projection_count = 0;
+  {
+    bool ret = std::ranges::contains(a.begin(), a.end(), 0, [&](int i) {
+      ++projection_count;
+      return i;
+    });
+    assert(ret);
+    assert(projection_count == 3);
+    projection_count = 0;
+  }
+  {
+    bool ret = std::ranges::contains(a, 0, [&](int i) {
+      ++projection_count;
+      return i;
+    });
+    assert(ret);
+    assert(projection_count == 3);
+  }
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  assert(test_nonconstexpr());
+
+  return 0;
+}
diff --git a/libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp b/libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp
index d17dce00..85fe6fb 100644
--- a/libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp
+++ b/libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp
@@ -75,6 +75,7 @@ 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::contains, in, x, &Bar::val);
   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);
diff --git a/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp b/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp
index 5c8aa01..139f199 100644
--- a/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp
+++ b/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp
@@ -75,6 +75,7 @@ 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::contains, in, x);
   test(std::ranges::ends_with, in, in2);
 #endif
   test(std::ranges::none_of, in, unary_pred);