1 (define (test-case actual expected)
2   (newline)
3   (display "Actual: ")
4   (display actual)
5   (newline)
6   (display "Expected: ")
7   (display expected)
8   (newline))
9 
10 (define (deep-reverse tree)
11   (cond ((null? tree) '())
12 	((not (pair? tree)) tree)
13 	(else (append
14 	       (deep-reverse (cdr tree))
15 	       (list (deep-reverse (car tree)))))))
16 
17 ;; (define x (list (list 1 2) (list 3 4)))
18 ;; (test-case (reverse x) '((3 4) (1 2)))
19 ;; (test-case (deep-reverse x) '((4 3) (2 1)))
20 
21 
22 ;;Exercise 2.28.  Write a procedure fringe that takes as argument a tree (represented as a list) and returns a list whose elements are all the leaves of the tree arranged in left-to-right order. For example,
23 
24 (define (fringe tree)
25   (cond ((null? tree) '())
26 	((not (pair? tree)) (list tree))
27 	(else (append (fringe (car tree))
28 		      (fringe (cdr tree))))))
29 
30 
31 (define x (list (list 1 2) (list 3 4)))
32 (test-case (fringe x) '(1 2 3 4))
33 (test-case (fringe (list x x)) '(1 2 3 4 1 2 3 4))