anchor.diff:  of chunks. The layers partition the set of all chunks in the BM.
   Chunks with no connections to layers below are visible (including
   constant and conditioning) chunks. The layered structure is used in
  -the single, bottom-up approximate inference pass. When instantiating a
  -DBM, VISIBLE-CHUNKS and HIDDEN-CHUNKS are inferred from LAYERS and
  +the single, bottom-up, approximate inference pass. When instantiating
  +a DBM, VISIBLE-CHUNKS and HIDDEN-CHUNKS are inferred from LAYERS and
   CLOUDS.")
      (clouds-up-to-layers
       :type list :reader clouds-up-to-layers
  
positive.code: (defmethod set-n-stripes (n-stripes (cloud cloud)))
  (defmethod set-max-n-stripes (max-n-stripes (cloud cloud)))
  
  (defun activate-cloud (cloud reversep &key (from-fn #'old-nodes) (to-fn #'nodes))
    "From CHUNK1 calculate the activations of CHUNK2 and _add_ them to
  CHUNK2. If REVERSEP then swap the roles of the chunks. FROM-FN and
  TO-FN are the accessors to use to get the nodes value arrays (one of
  
negative.code: 
  (defun hijack-means-to-activation (chunks clouds bm &key addp)
    "Set NODES of CHUNKS to the activations calculated from CLOUDS. Skip
  chunks that don't need activations. If ADDP don't zero NODES first,
  but add to it."
    (destructuring-bind (static-activations-context static-chunks)
        (or (rest (find bm *static-activation-contexts* :key #'first))
            (list (gensym) nil))
  