c2e31.ss

;; high-order-function version of square-tree

(define (tree-map proc tree)
  (map (lambda (sub-tree)
	 (if (pair? sub-tree)
	     (tree-map proc sub-tree)
	     (proc sub-tree)))
       tree))

(define (square-tree tree) (tree-map (lambda (x) (* x x)) tree))