generic-random/examples/generic.hs

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}

import GHC.Generics (Generic)
import Test.QuickCheck
import Generic.Random

data Tree a = Leaf | Node (Tree a) a (Tree a)
  deriving (Show, Generic)

instance Arbitrary a => Arbitrary (Tree a) where
  arbitrary = genericArbitrary' uniform

data Bush a = Tip a | Fork (Bush a) (Bush a)
  deriving (Show, Generic)

instance (Arbitrary a, BaseCase (Bush a)) => Arbitrary (Bush a) where
  arbitrary = genericArbitrary' (1 % (2 % ()))

main :: IO ()
main = do
  sample (arbitrary :: Gen (Tree ()))
  putStrLn ""
  sample (arbitrary :: Gen (Bush ()))