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