I am reading article "Fun with type functions" and I have a few questions regarding examples presented in it. Here is the code class Add a b where type SumTy a b add :: a -> b -> SumTy a b instance (Add Integer a) => Add Integer [a] where type SumTy Integer [a] = [SumTy Integer a] add x y = map (add x) y Here are my questions: 1. Is type "SumTy Integer [a]" visible outside 'Add' instance? 2. If yes, how would you create and instance of that type without using 'add' function? 3. Will function 'add x y' create the following structure [SumTy x y1, SumTy x y2, etc...]? If not, what is 'add x y' creates? 4. How to print the result of 'add x y'? Also, I understand the following "instance (Ord a) => Monad a where ...." as type of the 'a' must be an extension of type Ord. How shall I understand code below? "instance (Add Integer a) => Add Integer [a]" Thanks a lot.