diff --git a/source/mijin/util/concepts.hpp b/source/mijin/util/concepts.hpp
index a985a12..61d0490 100644
--- a/source/mijin/util/concepts.hpp
+++ b/source/mijin/util/concepts.hpp
@@ -66,6 +66,15 @@ concept deleter_type = requires(T deleter, TData* ptr)
     deleter(ptr);
 };
 
+template<typename T, typename TTo>
+concept implicitly_convertible = std::is_convertible_v<T, TTo>;
+
+template<typename T, template<typename...> typename TConstraint, typename... TArgs>
+concept not_type = !TConstraint<T, TArgs...>::value;
+
+template<typename T, typename TOther>
+concept not_same_as = not_type<T, std::is_same, TOther>;
+
 //
 // public functions
 //