gistfile1.txt

-- how I can do it

universe = fromList $ [("cat", ["animal"]), ("dog", ["animal"]), ("catdog", ["cat", "dog"])
isType x x = True
isType x y = case lookup universe x of
Nothing -> False
Just supertypes -> if y in supertypes then True else any (`isType` y) supertypes 

-- "cat" `isType` "animal" True
-- "cat" `isType` "catdog" False
-- "catdog" `isType` "animal" True
-- "ctadog" `isType` "anmial" False, but should be a compile error..

-- what I'd like to do, weird pseudocode

type family? Types

data Cat
data Dog
data CatDog
data Animal
universe = fromList $ [(Cat, [Animal]), (Dog, [Animal])...

Ctadog `isType` Anmial is now a typo