3.13 Exercise 3.13
Suppose we define the procedure
(define (make-cycle x) (set-cdr! (last-pair x) x))
Then, whe we try to compute (last-pair x), we get an infinite loop, because the end of x now points to the front of x. In other words, we will never come across a pair where the cdr is nil, so last-pair will never terminate.