anchor.diff:    (loop for c across string
       collect c))
   
  -(defun split (string &optional separator &key (ignore-case nil))
  +(defun split (string &optional (separator #\space) &key (ignore-case nil))
     "Returns a list of substrings of string
     divided by separator. Separator can be a string or
     a character.
  
positive.code:                    collect (subseq string i j)
                     while j)))
        (check-type string string)
        (cond ((null separator)
               (%split-by-char string #\space))
              ((typep separator 'character)
               (%split-by-char string separator))
              ((string= separator "") (chars string))
              ((typep separator 'string)
  
negative.code:   (if (> step 0)
      (let ((string-len (length string)))
        (loop for i = 0 then (+ i step)
              for j = step then (+ j step)
            collect (subseq string i (if (> j string-len)
                                      string-len
                                      j))
  