anchor.diff:  	     :in-sequence list)))
     list)
   
  -(defun |nsubstitute seq-type=list from-end=other end=other test-not=eq count=t key=identity|
  +(defun |nsubstitute seq-type=list from-end=nil end=other test-not=eq count=other key=identity|
       (newitem olditem list start end count)
     (let ((remaining list)
   	(start-bis start)
  
positive.code:     ;; skip a prefix indicated by start
      (loop until (zerop start-bis)
  	  until (endp remaining)
  	  do (setf remaining (cdr remaining)))
      (unless (zerop start-bis)
        (error 'invalid-start-index
  	     :datum start
  
negative.code: 	  do (setf remaining (cdr remaining))))
    list)
  
  (defun |nsubstitute seq-type=list from-end=nil end=nil test=other count=other key=identity|
      (newitem olditem list test start count)
    (let ((remaining list)
  	(start-bis start))
      ;; skip a prefix indicated by start
      (loop until (zerop start-bis)
  	  until (endp remaining)
  	  do (setf remaining (cdr remaining))
  	     (decf start-bis))
      (unless (zerop start-bis)
        (error 'invalid-start-index
  	     :datum start
  