gistfile1.diff

+    @tailrec
     private def advance : Boolean = {
       if (!rangeIter.hasNext || !biasIter.hasNext) return false
       last = rangeIter.next
       left = biasIter.next
-      if (left == 0) return advance
-      true
+      if (left != 0) return true
+      advance
     }
   }