[exercise] 8.3

Author: Dev-XYS

chapter08-Declaring-types-and-classes/3.hs

@@ -0,0 +1,10 @@
+data Tree a = Leaf a | Node (Tree a) (Tree a)
+
+count :: Tree a -> Int
+count (Leaf _) = 1
+count (Node l r) = count l + count r + 1
+
+balanced :: Tree a -> Bool
+balanced (Leaf _) = True
+balanced (Node l r) = abs (lcount - rcount) <= 1 && balanced l && balanced r
+ where lcount = count l; rcount = count r