anchor.diff:  (defparameter *operators* (fset:empty-map))
   
   (defclass operator (literal-token)
  -  ())
  +  ()
  +  (:documentation
  +   "A token class for operators.
  +
  +Operators are treated specially when tokenizing, but they aren't any
  +different from other literal tokens after tokenization is complete.
  +All the same, this class exists to help group them all together."))
   
   (defmacro define-operator (name string &optional (superclasses '(operator)) slots &body options)
     (check-type name symbol)
  
positive.code:     :accessor command-word-tokens)
     (evaluate-fn
      :initform nil
      :accessor command-word-evaluate-fn)))
  (defmethod print-object ((command-word command-word) stream)
    (format stream "#<~A ~S>" (class-name (class-of command-word)) (command-word-tokens command-word)))
  
  
negative.code:   ((parts :type vector
            :initform (required)
            :accessor compound-word-parts
            :initarg :parts))
    (:documentation
     "A token class that consists of several tokens combined into a
  single aggregate token."))
  (defmethod print-object ((compound-word compound-word) stream)
    (format stream "#<~A ~S>" (class-name (class-of compound-word)) (compound-word-parts compound-word)))
  
  (defgeneric assignment-word-name (assignment-word)
    (:documentation
     "Retrieve the name portion of the assignment.
  
  The name portion is the part that comes before the #\= character."))
  
  (defgeneric assignment-word-value-word (assignment-word)
    (:documentation
     "Retrieve the value portion of the assignment.
  
  The value portion is the part tat comes after the #\= character."))
  
  (defclass assignment-word (a-word)
    ((name
  