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