Trans.hs

{-# LANGUAGE FlexibleContexts           #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE StandaloneDeriving         #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
{-|
Module:      Instances.Data.Functor.Trans
Copyright:   (C) 2014-2016 Ryan Scott
License:     BSD-style (see the file LICENSE)
Maintainer:  Ryan Scott
Stability:   Provisional
Portability: GHC

Provides 'Arbitrary' instances for functor transformers.
-}
module Instances.Data.Functor.Trans () where

import Data.Functor.Compose  (Compose(..))
import Data.Functor.Constant (Constant(..))
import Data.Functor.Product  (Product(..))
import Data.Functor.Reverse  (Reverse(..))
import Data.Functor.Sum      (Sum(..))

import Prelude ()
import Prelude.Compat

import Test.QuickCheck (Arbitrary(..), oneof)

deriving instance Arbitrary (f (g a)) => Arbitrary (Compose f g a)
deriving instance Arbitrary a         => Arbitrary (Constant a b)
deriving instance Arbitrary (f a)     => Arbitrary (Reverse f a)

instance (Arbitrary (f a), Arbitrary (g a)) => Arbitrary (Product f g a) where
    arbitrary = Pair <$> arbitrary <*> arbitrary

instance (Arbitrary (f a), Arbitrary (g a)) => Arbitrary (Sum f g a) where
    arbitrary = oneof [InL <$> arbitrary, InR <$> arbitrary]