1 (define (tree->list-1 tree)
2   (if (null? tree)
3       '()
4       (append (tree->list-1 (left-branch tree))
5 	      (cons (entry tree)
6 		    (tree->list-1 (right-branch tree))))))
7 (define (tree->list-2 tree)
8   (define (copy-to-list tree result-list)
9     (if (null? tree)
10 	result-list
11 	(copy-to-list (left-branch tree)
12 		      (cons (entry tree)
13 			    (copy-to-list (right-branch tree)
14 					  result-list)))))
15   (copy-to-list tree '()))