Exercise 4.34.  Modify the driver loop for the evaluator so that lazy 
pairs and lists will print in some reasonable way. (What are you going 
to do about infinite lists?) You may also need to modify the 
representation of lazy pairs so that the evaluator can identify them in 
order to print them.

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A reasonable approach is to print some fixed number of elements, or as 
many elements as can fit on one line of the output device, followed by 
an ellipsis.  The cons, car, and cdr procedures can be modified to 
use a tagged list:

(define (cons x y) (list 'lazy (lambda (m) (m x y))))

(define (car l) ((cadr l) (lambda (x y) x)))
(define (cdr l) ((cadr l) (lambda (x y) y)))

The pair? procedure will also need to be modified.