;#5

(define (matrix a b c d)
  (cons a (cons b (cons c (cons d '())))))

(define (value mat index)
  (cond ((equal? index 'a) (car mat))
        ((equal? index 'b) (cadr mat))
        ((equal? index 'c) (caddr mat))
        ((equal? index 'd) (cadddr mat))
        (else "No such element")))

(define (compose-matrix mata matb)
  (define a (+
             (* (value mata 'a) (value matb 'a))
             (* (value mata 'b) (value matb 'c))))
  (define b (+
             (* (value mata 'a) (value matb 'b))
             (* (value mata 'b) (value matb 'd))))
  (define c (+
             (* (value mata 'c) (value matb 'a))
             (* (value mata 'd) (value matb 'c))))
  (define d (+
             (* (value mata 'c) (value matb 'b))
             (* (value mata 'd) (value matb 'd))))
  (cons a (cons b (cons c (cons d '())))))

(define (add-matrix mata matb)
  (define a (+ (value mata 'a) (value matb 'a)))
  (define b (+ (value mata 'b) (value matb 'b)))
  (define c (+ (value mata 'c) (value matb 'c)))
  (define d (+ (value mata 'd) (value matb 'd)))
  (cons a (cons b (cons c (cons d '())))))

(define (add-streams-matrix s1 s2)
  (cond ((null? s1) '())
        ((null? s2) '())
        (else (cons-stream (add-matrix (stream-car s1) (stream-car s2))
                           (add-streams-matrix (stream-cdr s1)
                                        (stream-cdr s2))))))

(define omat-stream (cons-stream (matrix 1 4 0 2) omat-stream))

(define (pi o-stream)
  (define (action strm a a-list outpt)
    (define (produce)
      (action strm
    (define consume)
    )
  (action o-stream 2))))