anchor.diff:          list)))
           
   ;;; p02
  +
   (defun my-but-last (list)
     "Find the last but one box of a list.
   Example:
  
positive.code:         (list (element-at (cdr list) (1- k)))))
          
  ;;; p04
  (defun my-length (list)
    "Find the number of elements of a list."
    (if list
  
negative.code:       acc))
        
  ;;; p06
  
  (defun palindrome-p (list)
    "Find out whether a list is a palindrome.
  A palindrome can be read forward or backward; e.g. (x a m a x)."
    (equal list (my-reverse list)))
    
  ;;; p07
  
  (defun my-flatten (list)
    "Flatten a nested list structure.
  Transform a list, possibly holding lists as elements into a `flat' list by replacing each list with its elements (recursively).
  