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module UsingQuickCheck where
import Test.QuickCheck
--
-- 1
--
half :: (Eq a, Fractional a) => a -> a
half x = x / 2
halfIdentity :: (Eq a, Fractional a) => a -> a
halfIdentity = (*2) . half
--
-- 2
--
-- for any list you apply sort to
-- this property should hold
listOrdered :: (Ord a) => [a] -> Bool
listOrdered xs =
snd $ foldr go (Nothing, True) xs
where go _ status@(_, False) = status
go y (Nothing, t) = (Just y, t)
go y (Just x, _) = (Just y, x >= y)
--
-- 3
--
plusAssociative :: (Ord a, Integral a) => a -> a -> a -> Bool
plusAssociative x y z = x + (y + z) == (x + y) + z
plusCommutative :: (Ord a, Integral a) => a -> a -> Bool
plusCommutative x y = x + y == y + x
--
-- 4
--
mulAssociative :: (Ord a, Integral a) => a -> a -> a -> Bool
mulAssociative x y z = x * (y * z) == (x * y) * z
mulCommutative :: (Ord a, Integral a) => a -> a -> Bool
mulCommutative x y = x * y == y * x
data Fool = Fulse
| Frue
deriving (Eq, Show)
data Fool' = Fulse' -- 2/3
| Frue' -- 1/3
deriving (Eq, Show)
instance Arbitrary Fool where
arbitrary = oneof [ return Fulse
, return Frue ]
instance Arbitrary Fool' where
arbitrary = frequency [ (3, return Fulse')
, (1, return Frue')]
|
