Hi Haskellers, After reading: https://stackoverflow.com/questions/34790721/where-is-the-set-type-class https://stackoverflow.com/questions/25191659/why-is-haskell-missing-obvious-... https://stackoverflow.com/questions/11508642/haskell-how-can-i-define-a-type... I can see why Haskell base does not provide typeclasses for sets. I'm wondering now though if I did create a Set typeclass what it would look like. There's several approaches using various language extensions and to me this approach using functional dependencies seems simpler than the other approaches: class Setish set a | set -> a where empty :: set singleton :: a -> set -- and so on. My question is how does the functional dependency in Setish interact with "extra" types needed for richer set operations like finding the powerset or taking a cartesian product? Something like: class Setish set a | set -> a where empty :: set singleton :: a -> set power_set :: set -> ?something product :: set -> ?something -> ?something -- and so on. TIA, Stu