From f813bbdf86b9d929d1219a40f697162d563d511e Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Wed, 29 Dec 2021 10:25:09 -0800
Subject: [PATCH] Implement heterogeneous `equal_range()` for multiset

---
 include/boost/unordered/unordered_set.hpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/boost/unordered/unordered_set.hpp b/include/boost/unordered/unordered_set.hpp
index 75003bf4..f710c702 100644
--- a/include/boost/unordered/unordered_set.hpp
+++ b/include/boost/unordered/unordered_set.hpp
@@ -1063,6 +1063,19 @@ 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<const_iterator, const_iterator> >::type
+      equal_range(const Key& k) const
+      {
+        node_pointer n = table_.find_node_impl(
+          table::policy::apply_hash(this->hash_function(), k), k,
+          this->key_eq());
+
+        return std::make_pair(
+          const_iterator(n), const_iterator(n ? table_.next_group(n) : n));
+      }
+
       // bucket interface
 
       size_type bucket_count() const BOOST_NOEXCEPT