First, the even function is only defined for integers, not general numeric types. Second, type classes are not objects. Ad hoc polymorphism is used to denote di

First, the even function is only defined for integers, not general numeric types. Second, type classes are not objects. Ad hoc polymorphism is used to denote different actions for different types but it doesn't break typing. The type integer is not the type object-integer: even? :: Integer -> Bool I am actually thoroughly confused where you got your type specification. Were you trying to say: class Integral a where even? :: a -> Bool even? :: (Integral a) => a -> Bool The reason why this disturbs me is because I find it difficult to draw the line at why even? should be even? :: (Integral a) => a -> Bool instead of even? :: Integer -> Bool. This doesn't make sense -- it's not a good use for typeclasses. There aren't many different categories of types which have a semantic notion of being even but a different implementation or type restriction. Even is just... even. It's just an operation on the integers. There's no need to bring ad hoc polymorphism in here.