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 (accumulate op initial sequence)
11   (if (null? sequence)
12       initial
13       (op (car sequence)
14 	  (accumulate op initial (cdr sequence)))))
15 
16 (define (accumulate-n op init seqs)
17   (if (null? (car seqs))
18       '()
19       (cons (accumulate op init (map car seqs))
20             (accumulate-n op init (map cdr seqs)))))
21 
22 (define (dot-product v w)
23   (accumulate + 0 (map * v w)))
24 
25 (define (matrix-*-vector m v)
26   (map (lambda (row)
27 	 (dot-product row v))
28        m))
29 
30 (define (transpose mat)
31   (accumulate-n cons '() mat))
32 
33 (define (matrix-*-matrix m n)
34   (let ((cols (transpose n)))
35     (map (lambda (m-row)
36 	   (matrix-*-vector cols m-row))
37 	 m)))
38 
39 (define m1 '((1 2 3) (4 5 6) (7 8 9)))
40 (define m2 '((3 1 9) (3 -2 -4) (7 0 5)))
41 (define m3 '((30 36 42) (66 81 96) (102 126 150)))
42 (define m4 '((3 1 9 -5 -2 1)
43 	     (3 -2 -4 0 4 8)
44 	     (7 0 5 2 3 6)))
45 (define m5 '((1 5 4)
46 	     (2 -1 -3)
47 	     (0 5 0)
48 	     (-4 0 8)
49 	     (5 -1 -2)
50 	     (-3 -2 6)))
51 (define m6 '((12 59 -21)
52 	     (-5 -23 58)
53 	     (-4 45 74)))
54 (define m7 '((1 2 0 -4 5 -3)
55 	     (5 -1 5 0 -1 -2)
56 	     (4 -3 0 8 -2 6)))
57 (define m8 '((3 3 7)
58 	     (1 -2 0)
59 	     (9 -4 5)
60 	     (-5 0 2)
61 	     (-2 4 3)
62 	     (1 8 6)))
63 (define v1 '(1 2 3))
64 (define v2 '(14 32 50))
65 (define v3 '(2 -1 4))
66 (define v4 '(41 -8 34))
67 
68 (test-case (matrix-*-vector m1 v1) v2)
69 (test-case (matrix-*-vector m2 v3) v4)
70 
71 
72 (test-case (transpose m5) m7)
73 (test-case (transpose m4) m8)
74 
75 (test-case (matrix-*-matrix m1 m1) m3)
76 (test-case (matrix-*-matrix m4 m5) m6)