From 19d2fe87387911e5510c193d07fec57f3300880f Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Mon, 20 Dec 2021 09:28:04 -0800
Subject: [PATCH] Implement heterogeneous `equal_range()` for multimap

---
 include/boost/unordered/unordered_map.hpp | 26 +++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/include/boost/unordered/unordered_map.hpp b/include/boost/unordered/unordered_map.hpp
index c9fd46d2..82cb7f80 100644
--- a/include/boost/unordered/unordered_map.hpp
+++ b/include/boost/unordered/unordered_map.hpp
@@ -1477,6 +1477,32 @@ namespace boost {
       std::pair<const_iterator, const_iterator> equal_range(
         const key_type&) const;
 
+      template <class Key>
+      typename boost::enable_if_c<detail::are_transparent<Key, H, P>::value,
+        std::pair<iterator, iterator> >::type
+      equal_range(const Key& key)
+      {
+        node_pointer p = table_.find_node_impl(
+          table::policy::apply_hash(this->hash_function(), key), key,
+          this->key_eq());
+
+        return std::make_pair(
+          iterator(p), iterator(p ? table_.next_group(p) : p));
+      }
+
+      template <class Key>
+      typename boost::enable_if_c<detail::are_transparent<Key, H, P>::value,
+        std::pair<const_iterator, const_iterator> >::type
+      equal_range(const Key& key) const
+      {
+        node_pointer p = table_.find_node_impl(
+          table::policy::apply_hash(this->hash_function(), key), key,
+          this->key_eq());
+
+        return std::make_pair(
+          const_iterator(p), const_iterator(p ? table_.next_group(p) : p));
+      }
+
       // bucket interface
 
       size_type bucket_count() const BOOST_NOEXCEPT