(load "2.36.txt") ; for accumulate and accumulate-n

(define (dot-product v w)
  (accumulate + 0 (map * v w)))

(define (matrix-*-vector m v)
  (map (lambda (row) (dot-product row v)) m))

(define (transpose m)
  (accumulate-n cons '() m))

(define (matrix-*-matrix m n)
  (let ((cols (transpose n)))
    (map (lambda (row) (map (lambda (col) (dot-product row col)) cols))
         m)))

; 1 ]=> (dot-product '(1 2 3) '(4 5 6))
; 
; ;Value: 32
; 
; 1 ]=> (transpose '((1 2 3) (4 5 6)))
; 
; ;Value: ((1 4) (2 5) (3 6))
; 
; 1 ]=> (matrix-*-vector '((1 2 3) (4 5 6)) '(-1 0 1))
; 
; ;Value: (2 2)
; 
; 1 ]=> (matrix-*-vector '((1 2 3) (6 5 4)) '(-1 0 1))
; 
; ;Value: (2 -2)
; 
; 1 ]=> (matrix-*-matrix '((1 2) (3 4) (5 6)) '((1 2) (-1 3)))
; 
; ;Value: ((-1 8) (-1 18) (-1 28))