1 665c255d 2023-08-04 jrmu (define (test-case actual expected)
 2 665c255d 2023-08-04 jrmu   (newline)
 3 665c255d 2023-08-04 jrmu   (display "Actual:   ")
 4 665c255d 2023-08-04 jrmu   (display actual)
 5 665c255d 2023-08-04 jrmu   (newline)
 6 665c255d 2023-08-04 jrmu   (display "Expected: ")
 7 665c255d 2023-08-04 jrmu   (display expected)
 8 665c255d 2023-08-04 jrmu   (newline))
 9 665c255d 2023-08-04 jrmu 
10 665c255d 2023-08-04 jrmu (define (mystery x)
11 665c255d 2023-08-04 jrmu   (define (loop x y)
12 665c255d 2023-08-04 jrmu     (if (null? x)
13 665c255d 2023-08-04 jrmu 	y
14 665c255d 2023-08-04 jrmu 	(let ((temp (cdr x)))
15 665c255d 2023-08-04 jrmu 	  (set-cdr! x y)
16 665c255d 2023-08-04 jrmu 	  (loop temp x))))
17 665c255d 2023-08-04 jrmu   (loop x '()))
18 665c255d 2023-08-04 jrmu 
19 665c255d 2023-08-04 jrmu ;; Explain what mystery does in general.
20 665c255d 2023-08-04 jrmu 
21 665c255d 2023-08-04 jrmu ;; mystery reverses the list x
22 665c255d 2023-08-04 jrmu 
23 665c255d 2023-08-04 jrmu (define v (list 'a 'b 'c 'd))
24 665c255d 2023-08-04 jrmu 
25 665c255d 2023-08-04 jrmu (define w (mystery v))
26 665c255d 2023-08-04 jrmu (test-case v '(a))
27 665c255d 2023-08-04 jrmu (test-case w '(d c b a))
28 665c255d 2023-08-04 jrmu