Anwendung I: Generierung von Bäumen

Variante A (explizite Implementierung)

data Tree a = Leaf | Branch { left :: Tree a 
           , key :: a , right :: Tree a }
instance Serial a => Serial ( Tree a ) where
    series = cons0 Leaf \/ cons3 Branch

Variante B (automatische Implementierung)

{-# LANGUAGE DeriveGeneric #-}
import Test.SmallCheck
import GHC.Generics
data Tree a = Leaf | Branch { left :: Tree a 
            , key :: a , right :: Tree a } 
    deriving Generics
instance Serial a => Serial (Tree a)