From 77c4a09a9bb0adc72c40a1323c67be28ec20c662 Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Tue, 21 Dec 2021 14:51:25 -0800
Subject: [PATCH] Implement heterogeneous `count()` for multimap

---
 include/boost/unordered/unordered_map.hpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/boost/unordered/unordered_map.hpp b/include/boost/unordered/unordered_map.hpp
index 20537bfa..f5d59c19 100644
--- a/include/boost/unordered/unordered_map.hpp
+++ b/include/boost/unordered/unordered_map.hpp
@@ -1487,6 +1487,18 @@ namespace boost {
 
       size_type count(const key_type&) const;
 
+      template <class Key>
+      typename boost::enable_if_c<detail::are_transparent<Key, H, P>::value,
+        size_type>::type
+      count(const Key& k) const
+      {
+        node_pointer n = table_.find_node_impl(
+          table::policy::apply_hash(this->hash_function(), k), k,
+          this->key_eq());
+
+        return n ? table_.group_count(n) : 0;
+      }
+
       std::pair<iterator, iterator> equal_range(const key_type&);
       std::pair<const_iterator, const_iterator> equal_range(
         const key_type&) const;