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EqInstances.hs
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EqInstances.hs
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module EqInstances where
data TisAnInteger =
TisAn Integer
instance Eq TisAnInteger where
(==) (TisAn x) (TisAn x') = x == x'
data TwoIntegers = Two Integer Integer
instance Eq TwoIntegers where
(==) (Two x1 x2) (Two x1' x2') = x1 == x1' && x2 == x2'
data StringOrInt =
TisAnInt Int
| TisAString String
deriving Show
instance Eq StringOrInt where
(==) (TisAnInt x) (TisAnInt x') = x == x'
(==) (TisAString x) (TisAString x') = x == x'
(==) _ _ = False
data Pair a =
Pair a a
deriving Show
instance Eq a => Eq (Pair a) where
(==) (Pair a1 a2) (Pair a1' a2') = a1 == a1' && a2 == a2'
data Tuple a b =
Tuple a b
deriving Show
instance (Eq a, Eq b) => Eq (Tuple a b) where
(==) (Tuple a1 b1) (Tuple a1' b1') = a1 == a1' && b1 == b1'
data Which a =
ThisOne a
| ThatOne a
deriving Show
instance Eq a => Eq (Which a) where
(==) (ThisOne a) (ThisOne a') = a == a'
(==) (ThatOne a) (ThatOne a') = a == a'
(==) _ _ = False
data EitherOr a b =
Hello a
| Goodbye b
deriving Show
instance (Eq a, Eq b) => Eq (EitherOr a b) where
(==) (Hello a) (Hello a') = a == a'
(==) (Goodbye b) (Goodbye b') = b == b'
(==) _ _ = False