anchor.diff:          list)))
           
   ;;; p02
  +
   (defun my-but-last (list)
     "Find the last but one box of a list.
   Example:
  
positive.code:         list)))
          
  ;;; p03
  (defun element-at (list k)
    "Find the K'th element of a list.
  The first element in the list is number 1.
  
negative.code:       0))
    
  ;;; p05
  
  (defun my-reverse (list &optional acc)
    "Reverse a list."
    (if list
  