From a87277c6e809f5526b792c3467188d8f184da580 Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Wed, 12 Jan 2022 15:47:25 -0800
Subject: [PATCH 1/2] Add tests for `unordered_set::contains()`

---
 test/unordered/contains_tests.cpp | 78 +++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/test/unordered/contains_tests.cpp b/test/unordered/contains_tests.cpp
index 032b1677..45bc59d9 100644
--- a/test/unordered/contains_tests.cpp
+++ b/test/unordered/contains_tests.cpp
@@ -169,9 +169,87 @@ void test_multimap()
   test_map_non_transparent_contains<non_transparent_multimap3>();
 }
 
+template <class UnorderedSet> void test_set_transparent_contains()
+{
+  count_reset();
+
+  UnorderedSet set;
+  bool contains = set.contains(0);
+  BOOST_TEST(!contains);
+
+  BOOST_TEST_EQ(key::count_, 0);
+
+  set.insert(0);
+  set.insert(0);
+  set.insert(0);
+  set.insert(1);
+
+  int const expected_key_count = key::count_;
+
+  contains = set.contains(0);
+  BOOST_TEST(contains);
+
+  contains = set.contains(1);
+  BOOST_TEST(contains);
+
+  contains = set.contains(2);
+  BOOST_TEST(!contains);
+
+  BOOST_TEST_EQ(key::count_, expected_key_count);
+}
+
+template <class UnorderedSet> void test_set_non_transparent_contains()
+{
+  count_reset();
+
+  UnorderedSet set;
+  bool contains = set.contains(0);
+  BOOST_TEST(!contains);
+  BOOST_TEST_EQ(key::count_, 1);
+
+  set.insert(0);
+  set.insert(0);
+  set.insert(0);
+  set.insert(1);
+
+  int key_count = key::count_;
+
+  contains = set.contains(0);
+  ++key_count;
+  BOOST_TEST(contains);
+
+  contains = set.contains(1);
+  ++key_count;
+  BOOST_TEST(contains);
+
+  contains = set.contains(2);
+  ++key_count;
+  BOOST_TEST(!contains);
+
+  BOOST_TEST_EQ(key::count_, key_count);
+}
+
+void test_set()
+{
+  typedef boost::unordered_set<key, transparent_hasher, transparent_key_equal>
+    transparent_set;
+
+  typedef boost::unordered_set<key, transparent_hasher, key_equal>
+    non_transparent_set1;
+  typedef boost::unordered_set<key, hasher, transparent_key_equal>
+    non_transparent_set2;
+  typedef boost::unordered_set<key, hasher, key_equal> non_transparent_set3;
+
+  test_set_transparent_contains<transparent_set>();
+  test_set_non_transparent_contains<non_transparent_set1>();
+  test_set_non_transparent_contains<non_transparent_set2>();
+  test_set_non_transparent_contains<non_transparent_set3>();
+}
+
 UNORDERED_AUTO_TEST (contains) {
   test_map();
   test_multimap();
+  test_set();
 }
 
 RUN_TESTS()

From f5d470c53179059b003fbd001e5a748bdb474947 Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Wed, 12 Jan 2022 15:47:34 -0800
Subject: [PATCH 2/2] Implement `unordered_set::contains()`

---
 include/boost/unordered/unordered_set.hpp | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/boost/unordered/unordered_set.hpp b/include/boost/unordered/unordered_set.hpp
index c66fef7e..0210056d 100644
--- a/include/boost/unordered/unordered_set.hpp
+++ b/include/boost/unordered/unordered_set.hpp
@@ -507,6 +507,23 @@ namespace boost {
       const_iterator find(CompatibleKey const&, CompatibleHash const&,
         CompatiblePredicate const&) const;
 
+      bool contains(key_type const& k) const
+      {
+        return table_.find_node_impl(
+          table::policy::apply_hash(this->hash_function(), k), k,
+          this->key_eq());
+      }
+
+      template <class Key>
+      typename boost::enable_if_c<detail::are_transparent<Key, H, P>::value,
+        bool>::type
+      contains(const Key& k) const
+      {
+        return table_.find_node_impl(
+          table::policy::apply_hash(this->hash_function(), k), k,
+          this->key_eq());
+      }
+
       size_type count(const key_type&) const;
 
       template <class Key>