What about a constructor from an existing std::array of key value pairs?

[gotnone]

What do you think about adding an additional constructor for the case where one already has the data array created?

diff --git a/include/constexpr_hash_map/constexpr_hash_map.hpp b/include/constexpr_hash_map/constexpr_hash_map.hpp
index c1b9d50..68d740b 100644
--- a/include/constexpr_hash_map/constexpr_hash_map.hpp
+++ b/include/constexpr_hash_map/constexpr_hash_map.hpp
@@ -42,6 +42,15 @@ public:
         static_assert(N == sizeof...(elements), "Elements size doesn't match expected size of a hash-map");
     }
 
+    /// @brief The only other construction that might be used, array must be provided in the constructor.
+    /// @param std::array<std::pair<K,V>, N>, cannot be empty
+    explicit constexpr hash_map(data_type arr) noexcept
+    : data{std::move(arr)}
+    {
+        static_assert(N > 0, "N should be positive");
+        static_assert(N == data.size(), "Array size doesn't match expected size of a hash-map");
+    }
+
     /// @brief Searches map for a given key and returns iterator.
     /// @param key key to be searched for
     /// @return constant iterator to an element (cend, if not found)

Someone with more experience template programming may find a way to deduce the N, K and V parameters from the std::array itself.

[gotnone]

This version fixes an issue in the static assert and provides a deduction guide.

diff --git a/include/constexpr_hash_map/constexpr_hash_map.hpp b/include/constexpr_hash_map/constexpr_hash_map.hpp
index c1b9d50..2a01401 100644
--- a/include/constexpr_hash_map/constexpr_hash_map.hpp
+++ b/include/constexpr_hash_map/constexpr_hash_map.hpp
@@ -42,6 +42,14 @@ public:
         static_assert(N == sizeof...(elements), "Elements size doesn't match expected size of a hash-map");
     }
 
+    /// @brief The only other construction that might be used, array must be provided in the constructor.
+    /// @param std::array<std::pair<K,V>, N>, cannot be empty
+    explicit constexpr hash_map(data_type arr) noexcept
+    : data{std::move(arr)}
+    {
+        static_assert(N > 0, "N should be positive");
+    }
+
     /// @brief Searches map for a given key and returns iterator.
     /// @param key key to be searched for
     /// @return constant iterator to an element (cend, if not found)
@@ -170,6 +178,9 @@ protected:
 private:
     data_type data;
 };
+
+template <std::size_t N, typename K, typename V>
+hash_map(std::array<std::pair<K, V>, N>) -> hash_map<N, K, V>;
 }  // namespace burda::ct
 
 #endif // CONSTEXPR_HASH_MAP_CONSTEXPR_HASH_MAP_HPP