anchor.diff:                     do (setf (cluster item) cluster)
                      unless (slot-boundp item 'cluster)
                      do (setf (cluster item) cluster)
  -                      (unless (noisep item)
  +                      (unless (noise-p item)
                           (append (neighbors item) stack))))))
  
positive.code:                    when (and (<= (gethash vertex (edges document)) epsilon)
                               (not (eq vertex document)))
                     collect vertex))
             (noisep (document)
               "A document must have a minimum number of neighbors to
                not qualify as noise."
               (setf (neighbors document) (range-query document))
  
negative.code:           with cluster = 0
            with stack = (list)
            unless (or (slot-boundp document 'cluster)
                       (noise-p document))
            do (incf cluster)
               (setf (cluster document) cluster)
               (setf stack (neighbors document))
  