title: units for rings in haskell in Num or Rational
body: <p>The Num class of haskell allows for quite general algebraic structures and looks like it's intended to be used to make rings. When speaking of a ring though, it's convenient to be able to explicitly mention its additional and multiplicative units - maybe Num.Zero and Num.One - is there such a thing to Num, another class that includes units or some other way that this is done?</p>