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{-# LANGUAGE FlexibleContexts #-}
module SkiFree where
import Test.QuickCheck
import Test.QuickCheck.Checkers
data S n a = S (n a) a deriving (Eq, Show)
instance ( Functor n
, Arbitrary (n a)
, Arbitrary a)
=> Arbitrary (S n a) where
arbitrary = S <$> arbitrary <*> arbitrary
--instance ( Applicative n
-- , Testable (n Property)
-- , EqProp a)
-- => EqProp (S n a) where
-- (S x y) =-= (S p q) =
-- (property $ (=-=) <$> x <*> p) .&. (y =-= q)
instance (Eq (n a), Eq a) => EqProp (S n a) where
(=-=) = eq
instance Functor n => Functor (S n) where
fmap f (S x y) = S (fmap f x) (f y)
instance Foldable n => Foldable (S n) where
foldMap f (S n a) = mappend (foldMap f n) (f a)
instance Traversable n => Traversable (S n) where
traverse f (S x y) = S <$> (traverse f x) <*> (f y)
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