1 (define (list-ref items n)
2   (if (= n 0)
3       (cat items)
4       (list-ref (cdr items) (- n 1))))
5 
6 (define (length items)
7   (define (length-ter a count)
8     (if (null? a)
9 	count
10 	(length-iter (cdr a) (+ 1 count))))
11   (length-iter items 0))
12 
13 (define (append list1 list2)
14   (if (null? list1)
15       list2
16       (cons (car list1)
17 	    (append (cdr list1) list2))))
18 
19 (define (last-pair l)
20   (cond ((null? l) (error "Empty List"))
21 	((null? (cdr l)) l)
22 	(else (last-pair (cdr l)))))
23 
24 (define (test-case actual expected)
25   (load-option 'format)
26   (newline)
27   (format #t "Actual: ~A Expected: ~A" actual expected))
28 
29 ;; (test-case (last-pair (list 23 72 149 34)) '(34))
30 ;; ;; (test-case (last-pair '()) (error "Empty List"))
31 ;; (test-case (last-pair (list 4)) '(4))
32 
33 (define (reverse l)
34   (if (null? l)
35       '()
36       (append
37        (reverse (cdr l))
38        (car l))))
39 
40 (test-case (reverse (list 1 4 9 16 25)) '(25 16 9 4 1))
41 (test-case (reverse (list)) '())
42 (test-case (reverse (list 4)) '(4))