tree.hs

data Tree a = Empty | Tree a (Tree a) (Tree a) deriving (Show)

singleton :: a -> Tree a
singleton x = Tree x Empty Empty

addToTree :: (Ord a) => a -> Tree a -> Tree a
addToTree new Empty = singleton new
addToTree new (Tree value left right)
  | new < value = Tree value (addToTree new left) right
  | otherwise = Tree value left (addToTree new right)

searchTree :: (Ord a) => a -> Tree a -> Maybe (Tree a)
searchTree _ Empty = Nothing
searchTree x cur@(Tree value left right)
  | x == value = Just cur
  | x < value  = searchTree x left
  | x > value  = searchTree x right