[Haskell-cafe] positive Int

as far as i know, the haskell standard does not define a basic Int type that is limited to positive numbers. would a type of this kind not potentially allow us to make stronger verification statements about certain functions? for example, 'length' returns an Int, but in reality it must always return a value 0 or greater. a potential counter-argument would be the need to possibly redefine Ord etc for this more narrow type...