BinaryTree.dcl

definition module BinaryTree

:: BinaryTree a = Node a (BinaryTree a) (BinaryTree a) | Leaf

(!!!) infixl 9 :: (BinaryTree a) Int -> a

BinaryTree.icl

implementation module BinaryTree
import StdEnv

(!!!) infixl 9 :: (BinaryTree a) Int -> a
(!!!) tree n = f root tree where
    f [] (Node a _ _) = a
    f [x:xs] (Node _ tl tr)
        | x == 0 = f xs tl
        | x == 1 = f xs tr
    root = (tl o f [] o (+) 1) n where
        f xs 0 = xs
        f xs n = f [n rem 2:xs] (n/2)