anchor.diff:      (:constructor defwff (operator wffs)))
     operator wffs)
   
  -(defun cnf-rule (facts implications)
  -  (defwff 'or (demorgan (defwff 'not facts)) (demorgan implications)))
  +(defun cnf-rule (facts-wff implications-wff)
  +  (defwff 'or (list (demorgan (defwff 'not facts-wff))
  +                    (demorgan implications-wff))))
   
   (defun demorgan (wff &aux
                        (operator (if (wff-p wff) (wff-operator wff)))
  
positive.code:           ((notevery #'fact-p operand)
             (defwff operator (mapcar #'(lambda (x) (demorgan x)) operand)))
            ('else wff))))
  
negative.code: ;;; Resolution-based Q&A system.
  ;;;
  ;;; Pranav Ravichandran <me@onloop.net>
  
  (defstruct
    (var
      (:constructor var (x))) x)
  
  (defstruct
    (fact
  