Ex2_31.scm

(define (tree-map func tree)
  (map (lambda (subtree)
	 (if (pair? subtree)
	     (tree-map func subtree)
	     (func subtree)))
       tree))

(define (square x) (* x x))

(define (square-tree tree) (tree-map square tree))

(square-tree (list 1
		   (list 2 (list 3 4) 5)
		   (list 6 7)))