; Infinite streams
(define ones (cons 1 (delay ones)))
(define nat (cons 1
		 (delay (+str ones nat))))
(define (+str s1 s2)
	(cons (+ (car s1) (car s2))
		(delay (+str
			(force (cdr s1))
			(force (cdr s2))))))
(define (filter p s)
   (if (p (car s))
	(cons (car s)
	    (delay (filter p
			(force (cdr s)))))
	(filter p (force  (cdr s)))))
(define fibs
	(letrec
		((fibgen (lambda (a b) 
		(cons a (delay (fibgen b 
					(+ a b)))))))
	(fibgen 0 1)))
(define (primes)
	(letrec ((sieve (lambda (s)
	  (cons (car s)
	 	(delay (sieve (filter 
		  (lambda (n) 
	(> (remainder n (car s)) 0))
		(force (cdr s)))))))))
	(sieve (force (cdr nat)))))
(define (print s)
	(write (car s))
	(print (force (cdr s))))