(define int-reci
	  (stream-map (lambda (x)
	  	            (if (even? x)
	  	            	  (- (/ 1 x))
	  	            	  (/ 1 x)))
	  	          integers))

	(define ln2 
		(cons-stream 1.0
			           (add-stream (stream-cdr int-reci)
			           	           ln2)))