(define (lookup key set) |
(if (null? set) |
false |
(let ((e (entry set))) |
(let ((entry-key (car e)) |
(entry-val (cdr e))) |
(cond ((= key entry-key) entry-val) |
((< key entry-key) (lookup key (left-branch set))) |
((> key entry-key) (lookup key (right-branch set)))))))) |