use bitwise-bit-set? in day 3

day-3.scm

@@ -8,8 +8,7 @@
       (lambda (index number)
 	(let iterate [(bit 0)]
 	  (when (< bit 12)
-	    (when (= 0 (bitwise-and number 
-				  (bitwise-arithmetic-shift-left 1 bit)))
+	    (when (not (bitwise-bit-set? number bit))
 	      (vector-set! zeroes bit 
 			   (+ 1 (vector-ref zeroes bit))))
 	    (iterate (+ 1 bit)))))