(define ones (cons-stream 1 ones))

(1 . #<promise>)

(stream-section 7 ones)

(1 1 1 1 1 1 1)

(define (integers-starting-from n)
 (cons-stream n 
  (integers-starting-from (+ n 1))))

(define nat-nums
  (integers-starting-from 1))

(stream-section 10 nat-nums)

(1 2 3 4 5 6 7 8 9 10)

(define nat-nums 
 (cons-stream 1 
  (add-streams ones nat-nums)))

(stream-section 10 nat-nums)

(1 2 3 4 5 6 7 8 9 10)

(define fibs
  (cons-stream 0
    (cons-stream 1
      (add-streams (tail fibs) fibs))))

(stream-section 15 fibs)

(0 1 1 2 3 5 8 13 21 34 55 89 144 
 233 377)