anchor.diff:  
   (find-route '(nreverse lst) *first-impl*)
   (find-route 'lst *first-impl*)
  -
  -(defun rdiff (base modified refmark)
  -  (let ((subtrees (collect-effective-refs base)))
  -    (labels ((rec (code)
  -               (aif (find code subtrees :key #'last1 :test #'equal)
  -                 (cons refmark (car it))
  -                 (if (atom code) code
  -                   (mapcar #'rec code)))))
  -      (rec modified))))
  -
  -(rdiff *first-impl* *second-impl* 'ref)
  -(rdiff *first-impl* *first-impl* 'ref)
  -(rdiff '(a (x y z) b c) '(print (a (x y z) b c)) 'ref)
  -(rdiff '(a (x y z) b c) '(a (x s z) b c) 'ref)
   
   (defun levenshtein-distance (str0 str1 &key (test #'eql))
     (if (not (shorter-or-equal str0 str1))
  
positive.code:           (if (consp sub)
              (green (third (find (cdr sub) (collect-effective-refs base) :key #'car)))
              (green sub))))))
  
  (with-open-file (out "tmp.html" :direction :output :if-does-not-exist :create :if-exists :supersede)
    (let ((*standard-output* out))
      (write-line "<html> <head><title></title></head> <body bgcolor=\"000000\"><p>")
      (showdiff *first-impl* *first-impl* 0)
      (write-line "<br/>")
      (mapc (lambda (x)
              (white (format nil "~a : " x))
              (showdiff *first-impl* `(progn ,*third-impl*) x)
              (write-line "<br/>"))
            (iota 8))
      (write-line "</p></body></html>")))
  
  (with-open-file (out "tmp.html" :direction :output :if-does-not-exist :create :if-exists :supersede)
    (let ((*standard-output* out))
      (write-line "<html> <head><title></title></head> <body bgcolor=\"000000\"><p>")
      (mapc (lambda (n)
              (white (format nil "~a : " n))
              (showdiff
                '(lambda (x)
                   (showdiff *first-impl* *second-impl* x)
                   (write-line "br/>"))
                '(lambda (x)
                   (princ x)
                   (showdiff *first-impl* *second-impl* x)
                   (write-line "br/>"))
                n)
              (write-line "<br/>"))
            (iota 4))
      (write-line "</p></body></html>")))
  
  (defun route-normalize (raw-route)
    (drop (reverse raw-route)))
  
negative.code: 
  (retrieve-by-route '(a b (x (s t u) y z) c) '(2 1 2 1))
  
  (defun white (x)
    (format t "<font color=\"#ffffff\">~%<pre> ~a</pre>~%</font>" x))
  
  