anchor.diff:      (find-node-by-transitions it properties)))
   
   ;;;
  -;;; Creating molds
  -;;;
  -(defun ensure-mold (parents)
  +;;; Mold API -- Retrieval and Automatic Creation of Molds and Nodes
  +;;;
  +(defun ensure-toplevel-mold (parents)
     "Returns the mold for PARENTS, creating and caching a new one if necessary."
     (check-list-type parents object)
     (or (find-mold parents)
         (setf (find-mold parents)
  -            (aprog1 (make-mold parents)
  -              (setf (mold-initial-node it)
  -                    (make-node :mold it))))))
  +            (make-mold parents))))
   
   (defun ensure-transition (node property-name)
     "Returns the transition from NODE indexed by PROPERTY-NAME, creating and
  
positive.code:   (check-type node node)
    (check-type property-name property-name)
    (or (find-transition node property-name)
        (aconsf (node-transitions node) property-name
                (make-node :mold (node-mold node)
                           :properties (cons property-name
                                             (node-properties node))))))
  
  (defun ensure-mold (parents properties)
    (or (find-mold parents properties)
  
negative.code:         (awhen (some (fun (find-transition start-node _)) path)
            (find-node-by-transitions it path)))))
  
  (defun find-mold-node (parents properties)
    "Searches the mold cache for one with parents PARENTS and properties PROPERTIES,
  returning that mold if found, or NIL on failure."
  