Practice 3.64
(define (stream-limit stream n)
(let ((a (stream-car stream))
(b (stream-car (stream-cdr stream))))
(if (< (abs (- a b)) n)
b
(stream-limit (stream-cdr stream) n))))
(define (stream-limit stream n)
(let ((a (stream-car stream))
(b (stream-car (stream-cdr stream))))
(if (< (abs (- a b)) n)
b
(stream-limit (stream-cdr stream) n))))