SICP Exercise 3.51 showing delayed evaluation

Exercise 3.51.  In order to take a closer look at delayed evaluation, we will use the following procedure, which simply returns its argument after printing it:

(define (show x)
  (display-line x)
  x)

What does the interpreter print in response to evaluating each expression in the following sequence?⁵⁹


(define x (stream-map show (stream-enumerate-interval 0 10)))
(stream-ref x 5)
(stream-ref x 7)

SOLUTION

The code and tests are here.

Note: I spent a lot of time tracing through the logic to see what really happens here. The delayed evaluation of items in streams combined with new streams being produced in procedure stream-map makes it really confusing. 

Also, note that in Racket, both the car part and the cdr part of the stream are delayed evaluations until the point of need.