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; Exercise 2.33
(newline) (display "Exercise 2.37") (newline)
; -- Defs --
(define nil ())
(define (accumulate op initial sequence)
(if (null? sequence)
(op (car sequence)
(accumulate op initial (cdr sequence)))))
(define (accumulate-n op init seqs)
(if (null? (car seqs))
(cons (accumulate op init (map car seqs))
(accumulate-n op init (map cdr seqs)))))
; -- Start --
(define V (list 3 2 1 0))
(define W (list 1 1 1 1))
(define M (list
(list 0 1 2 3)
(list 1 2 3 4)
(list 2 3 4 5)))
(define (dot-product v w)
(accumulate + 0 (map * v w)))
(define (matrix-*-vector m v)
(map (lambda (x) (dot-product x v)) m))
(define (transpose mat)
(accumulate-n (lambda (x acc) (cons x acc)) nil mat))
(define (matrix-*-matrix m n)
(let ((cols (transpose n)))
(map (lambda (v) (matrix-*-vector cols v)) m)))
(display (dot-product V W)) (newline)
(display (matrix-*-vector M V)) (newline)
(display (transpose M)) (newline)
(display (matrix-*-matrix M (transpose M))) (newline)