Lame Binary Tree in Haskell

lamebtree.hs

module Main where

data List a = Nil | Cons a (List a)
    deriving (Show)

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

append :: (Ord a) => Tree a -> a -> Tree a
append Empty a = Node a (Empty) (Empty)
append (Node item left right) a 
    | a < item = (Node item (append left a) right)
    | a > item = (Node item left (append right a))
    | otherwise = (Node item left right)

btree = Node 100 Empty Empty
btree2 = append btree 50
btree3 = append btree2 30
btree4 = append btree3 80
    
main = print $ btree4