[plt-scheme] stream-delay question

Hi,

I'm trying to learn srfi-40 (streams), and I don't understand 
stream-delay.  The srfi doc uses it in an example stream `from0'.  Can 
someone give me an example where from0 and from0/no-delay behave 
differently?


(require (lib "40.ss" "srfi"))

(define from0
   (let loop ((x 0))
     (stream-delay
      (stream-cons x (loop (+ x 1))))))

(define from0/no-delay
   (let loop ((x 0))
     (stream-cons x (loop (+ x 1)))))


thanks,

Rob