anchor.diff:  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   
   
  -
  -(defthm neg-sem-correct
  +(defthm negation-semantics-correct
     (implies (and (modelp m)
  -                (pdl-formulap m (get-prop-atoms m) (get-prog-atoms m)))
  -           (implies (equal (len f) 2)
  -                    (not (pdl-satisfies-aux m w f nil t)))))
  +                (pdl-formulap m (get-prop-atoms m) (get-prog-atoms m))
  +                (equal (first f) '~))
  +           (not (pdl-satisfies m w f))))
   
   
   
  
positive.code:             t
            (pdl-satisfies-aux m w f (cdr worlds) nil))
        nil)))
  ;)
  
  
  
  
negative.code: ; to
  ; (defun foobar (A B C) (if C foo-body bar-body))
  
  (defun pdl-satisfies-aux (m w f worlds evaling-formula)
    (declare (xargs :well-founded-relation l<
                    :measure (list (acl2-count f) (acl2-count worlds))))
  