(define ones (cons-stream 1 ones))

(define (add-streams first second)
  (stream-map + first second))

(define integers (cons-stream 1 (add-streams ones integers)))

(define (display-stream stream)
  (display "[")
  (stream-for-each (lambda (x) (display x) (display " "))
		   stream)
  (display "]"))

(define (display-stream-start stream i)
  (if (<= i 0)
      (newline)
      (begin
	(display (stream-car stream))
	(display " ")
	(display-stream-start (stream-cdr stream) (-1+ i)))))

(display-stream-start integers 10)

; Ex. 3.50 in the book
; stream map with multiple argument streams
;(define (stream-map proc . argstreams)
;  (if (<????>)
;      the-empty stream
;      (<????>
;       (apply proc (map <????> argstreams))
;       (apply stream-map
;	      (cons proc (map <????> argstreams))))))

;; this version of stream-map-n assumes that the argument streams
;; are the same length  	      

(define (stream-map-n proc . argstreams)
  (if (stream-null? (car argstreams))
      the-empty-stream
      (cons-stream
       (apply proc (map stream-car argstreams))
       (apply stream-map-n
	      (cons proc (map stream-cdr argstreams))))))

(define (stream-enumerate-interval low high)
  (if (> low high)
      the-empty-stream
      (cons-stream
       low
       (stream-enumerate-interval (+ low 1) high))))


(define mysum (stream-map-n + (stream-enumerate-interval 1 10)
	    (stream-enumerate-interval 5 14)
	    (stream-enumerate-interval 8 17)))

(stream-car (stream-cdr mysum))