anchor.diff:           ("rv" (list :ffr :ffl))
            (("ffr" "ffl" "fsr" "fsl" "bbr" "bbl" "bsr" "bsl")
             (list (force-exist-symbol effective-directions :keyword)))
  -         (t (error (format nil "No match for directional modifier ~a found." effective-directions))))))
  +         (t (error "No match for directional modifier ~a found." effective-directions)))))
       (:hybrid
        (if (equal "" (remove-if-not #'(lambda (p) (find p "brflvs")) modifier-string))
            (list :bl :b :br :fl :f :fr :r :l)
  
positive.code:                             ((#\Q #\K) :hybrid)
                              (#\R :orthogonal)
                              (#\B :diagonal)
                              (t (error (format nil "Landmark ~s not found." landmark)))))
            ((apply #'= displacement) :diagonal)
            ((some #'zerop displacement) :orthogonal)
            (t :hippogonal))))
  
negative.code:          ("f" (list :fr :fl))
           ("l" (list :fl :bl))
           (("br" "bl" "fr" "fl") (list (force-exist-symbol effective-directions :keyword)))
           (t (error "No match for directional modifier ~a found." effective-directions)))))
      (:hippogonal
       (let ((effective-directions (remove-if-not #'(lambda (p) (find p "brflvsh")) modifier-string)))
         (case-using-equal effective-directions
  