diff --git a/source/mijin/util/traits.hpp b/source/mijin/util/traits.hpp
index e96452f..aaa3141 100644
--- a/source/mijin/util/traits.hpp
+++ b/source/mijin/util/traits.hpp
@@ -121,6 +121,24 @@ using copy_volatile_t = std::conditional_t<std::is_volatile_v<TFrom>, std::add_v
 template<typename TFrom, typename TTo>
 using copy_cv_t = copy_const_t<TFrom, copy_volatile_t<TFrom, TTo>>;
 
+template<typename TActual, typename TDelay>
+using delay_type_t = TActual;
+
+
+template<std::size_t I, typename TArg, typename... TArgs>
+struct TypeAtHelper
+{
+    using type_t = std::conditional_t<I == 0, TArg, TypeAtHelper<I-1, TArgs...>>;
+};
+
+template<std::size_t I, typename TArg>
+struct TypeAtHelper<I, TArg>
+{
+    using type_t = std::enable_if_t<I == 0, TArg>;
+};
+template<std::size_t I, typename... TArgs>
+using type_at_t = TypeAtHelper<I, TArgs...>::type_t;
+
 //
 // public functions
 //