From ba27bd294e4b6fdd325265413c63a88b10ed1b6e Mon Sep 17 00:00:00 2001
From: WeHaveCookie <quentin.gerry@gmail.com>
Date: Wed, 7 Nov 2018 16:29:09 +0100
Subject: [PATCH 1/2] try_emplace c++17 feature

---
 flat_hash_map.hpp | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/flat_hash_map.hpp b/flat_hash_map.hpp
index a8723ee..3b4b3cc 100644
--- a/flat_hash_map.hpp
+++ b/flat_hash_map.hpp
@@ -1384,6 +1384,29 @@ class flat_hash_map
         return insert_or_assign(std::move(key), std::forward<M>(m)).first;
     }
 
+	template<typename... Args>
+	std::pair<typename Table::iterator, bool> try_emplace(const key_type & key, Args&&... args)
+	{
+		return this->try_emplace_impl(key, std::forward<Args>(args)...);
+	}
+
+	template<typename... Args>
+	std::pair<typename Table::iterator, bool> try_emplace(key_type && key, Args&&... args)
+	{
+		return try_emplace_impl(std::forward<key_type>(key), std::forward<Args>(args)...);
+	}
+
+	template<typename... Args >
+	typename Table::iterator try_emplace(typename Table::const_iterator, const key_type & key, Args&&... args)
+	{
+		return try_emplace(key, std::forward<Args>(args)...).first;
+	}
+	template<typename... Args>
+	typename Table::iterator try_emplace(typename Table::const_iterator, key_type && key, Args&&... args)
+	{
+		return try_emplace(std::forward<key_type>(key), std::forward<Args>(args)...).first;
+	}
+
     friend bool operator==(const flat_hash_map & lhs, const flat_hash_map & rhs)
     {
         if (lhs.size() != rhs.size())
@@ -1411,6 +1434,14 @@ class flat_hash_map
             return V();
         }
     };
+
+	template <typename KeyType = key_type, class... Args>
+	std::pair<typename Table::iterator, bool> try_emplace_impl(KeyType&& key, Args&&... args) {
+		auto res = this->find(key);
+		if (res == this->end())
+			return this->emplace(std::forward<KeyType>(key), std::forward<Args>(args)...);
+		return { { res }, false };
+	}
 };
 
 template<typename T, typename H = std::hash<T>, typename E = std::equal_to<T>, typename A = std::allocator<T> >

From 6141c31620d102f2bc7ec73525bffa19c2896907 Mon Sep 17 00:00:00 2001
From: WeHaveCookie <quentin.gerry@gmail.com>
Date: Wed, 7 Nov 2018 16:55:40 +0100
Subject: [PATCH 2/2] Try_emplace for bytell & unordered map

---
 bytell_hash_map.hpp | 31 +++++++++++++++++++++++++++++++
 unordered_map.hpp   | 31 +++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/bytell_hash_map.hpp b/bytell_hash_map.hpp
index 9c9a246..9afaa8c 100644
--- a/bytell_hash_map.hpp
+++ b/bytell_hash_map.hpp
@@ -1153,6 +1153,29 @@ class bytell_hash_map
         return insert_or_assign(std::move(key), std::forward<M>(m)).first;
     }
 
+	template<typename... Args>
+	std::pair<typename Table::iterator, bool> try_emplace(const key_type & key, Args&&... args)
+	{
+		return this->try_emplace_impl(key, std::forward<Args>(args)...);
+	}
+
+	template<typename... Args>
+	std::pair<typename Table::iterator, bool> try_emplace(key_type && key, Args&&... args)
+	{
+		return try_emplace_impl(std::forward<key_type>(key), std::forward<Args>(args)...);
+	}
+
+	template<typename... Args >
+	typename Table::iterator try_emplace(typename Table::const_iterator, const key_type & key, Args&&... args)
+	{
+		return try_emplace(key, std::forward<Args>(args)...).first;
+	}
+	template<typename... Args>
+	typename Table::iterator try_emplace(typename Table::const_iterator, key_type && key, Args&&... args)
+	{
+		return try_emplace(std::forward<key_type>(key), std::forward<Args>(args)...).first;
+	}
+
     friend bool operator==(const bytell_hash_map & lhs, const bytell_hash_map & rhs)
     {
         if (lhs.size() != rhs.size())
@@ -1180,6 +1203,14 @@ class bytell_hash_map
             return V();
         }
     };
+
+	template <typename KeyType = key_type, class... Args>
+	std::pair<typename Table::iterator, bool> try_emplace_impl(KeyType&& key, Args&&... args) {
+		auto res = this->find(key);
+		if (res == this->end())
+			return this->emplace(std::forward<KeyType>(key), std::forward<Args>(args)...);
+		return { { res }, false };
+	}
 };
 
 template<typename T, typename H = std::hash<T>, typename E = std::equal_to<T>, typename A = std::allocator<T> >
diff --git a/unordered_map.hpp b/unordered_map.hpp
index 5e6e876..462b590 100644
--- a/unordered_map.hpp
+++ b/unordered_map.hpp
@@ -778,6 +778,29 @@ class unordered_map
         return emplace(key_type(), convertible_to_value());
     }
 
+	template<typename... Args>
+	std::pair<typename Table::iterator, bool> try_emplace(const key_type & key, Args&&... args)
+	{
+		return this->try_emplace_impl(key, std::forward<Args>(args)...);
+	}
+
+	template<typename... Args>
+	std::pair<typename Table::iterator, bool> try_emplace(key_type && key, Args&&... args)
+	{
+		return try_emplace_impl(std::forward<key_type>(key), std::forward<Args>(args)...);
+	}
+
+	template<typename... Args >
+	typename Table::iterator try_emplace(typename Table::const_iterator, const key_type & key, Args&&... args)
+	{
+		return try_emplace(key, std::forward<Args>(args)...).first;
+	}
+	template<typename... Args>
+	typename Table::iterator try_emplace(typename Table::const_iterator, key_type && key, Args&&... args)
+	{
+		return try_emplace(std::forward<key_type>(key), std::forward<Args>(args)...).first;
+	}
+
     friend bool operator==(const unordered_map & lhs, const unordered_map & rhs)
     {
         if (lhs.size() != rhs.size())
@@ -805,6 +828,14 @@ class unordered_map
             return V();
         }
     };
+
+	template <typename KeyType = key_type, class... Args>
+	std::pair<typename Table::iterator, bool> try_emplace_impl(KeyType&& key, Args&&... args) {
+		auto res = this->find(key);
+		if (res == this->end())
+			return this->emplace(std::forward<KeyType>(key), std::forward<Args>(args)...);
+		return { { res }, false };
+	}
 };
 
 template<typename T, typename H = std::hash<T>, typename E = std::equal_to<T>, typename A = std::allocator<T> >