sicp-ex-3.59

meteorgan



a)
(define (integrate-series s)
              (stream-map * (stream-map / ones integers) s))
b)
(define sine-series (cons-stream 0 (integrate-series cosine-series)))
(define cosine-series (cons-stream 1 (integrate-series (scale-stream sine-series -1))))

shawn



a)
(define (integrate-series s)
              (stream-map /  s integers))

Here's a simpler version of a).

Sphinxsky

  
  
  
  
  
  
 ;; a) 
 (define (integrate-series stream) 
     (stream-map / stream integers)) 
 ;; b) 
 (define cosine-series 
     (cons-stream 1 (stream-map - (integrate-series sine-series)))) 
 (define sine-series 
     (cons-stream 0 (integrate-series cosine-series))) 
  
  
 ;; other way to exp 
 (define exp-series 
     (stream-map / ones (cons-stream 1 factorials)))

; (a
(define (integrate-series s)
 (stream-map / s integers))
(define exp-series (cons-stream 1
                    (integrate-series exp-series)))
; (b
(define (filter-odd s) (cons-stream (stream-car s) (filter-odd (stream-cdr (stream-cdr s)))))
(define (filter-even s) (cons-stream (stream-car (stream-cdr s)) (filter-even (stream-cdr (stream-cdr s)))))
(define s-11 (cons-stream 1 (stream-map (lambda (e)
                                      (if (= 1 e)
                                       -1
                                       1)) s-11)))
(define cosine-series (stream-map * s-11
                        (filter-odd exp-series)))
(define sine-series (stream-map * s-11
                        (filter-even exp-series)))