From a26e1c0f417f216183bdbe4cf21fa542290f70c4 Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Tue, 11 Jan 2022 09:40:47 -0800
Subject: [PATCH] Implement `unordered_map::contains()`

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

diff --git a/include/boost/unordered/unordered_map.hpp b/include/boost/unordered/unordered_map.hpp
index f5d59c19..a7765fe7 100644
--- a/include/boost/unordered/unordered_map.hpp
+++ b/include/boost/unordered/unordered_map.hpp
@@ -796,6 +796,23 @@ namespace boost {
       const_iterator find(CompatibleKey const&, CompatibleHash const&,
         CompatiblePredicate const&) const;
 
+      bool contains(const key_type& 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>