data LinkedTree a
	= EmptyTree
	| Node a (LinkedTree a) (LinkedTree a) (LinkedTree a)
 
root = Node 1 l r EmptyTree
	where
		l = Node 2 EmptyTree EmptyTree root
		r = Node 3 EmptyTree EmptyTree root
 
instance Show a => Show (LinkedTree a) where
	show EmptyTree = "{}"
	show (Node x EmptyTree EmptyTree _) = "{" ++ show x ++ "}"
	show (Node x l r _) = "{" ++ show x ++ " " ++ show l ++ " " ++ show r ++ "}"
 
left   (Node _ l _ _) = l
right  (Node _ _ r _) = r
parent (Node _ _ _ p) = p
 
main = do
	print root
	let rootLeft = left root
	print rootLeft
	print $ parent rootLeft
 

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