anchor.diff:  
                          (do-audio-file f
                            (lambda (s)
  -                           (cond ((typep s 'id3:mp3-file)
  -                                  (incf mp3-count))
  -                                 ((typep s 'flac:flac-file)
  -                                  (incf flac-count))
  -                                 ((typep s 'm4a:mp4-file)
  -                                  (incf mp4-count))
  -                                 ((null s)
  -                                  (incf other-count)))
  +                           (typecase s
  +                             (id3:mp3-file
  +                              (incf mp3-count))
  +                             (flac:flac-file
  +                              (incf flac-count))
  +                             (m4a:mp4-file
  +                              (incf mp4-count))
  +                             (otherwise
  +                              (incf other-count)))
                              (when (and (not (null s)) func)
                                (funcall func s)))))))))
   
  
positive.code:                                (do-audio-file
                                   f
                                   (lambda (s)
                                     (cond ((typep s 'id3:mp3-file)
                                            (incf mp3-count))
                                           ((typep s 'flac:flac-file)
                                            (incf flac-count))
                                           ((typep s 'm4a:mp4-file)
                                            (incf mp4-count))
                                           ((null s)
                                            (incf other-count)))
                                     (when (and (not (null s)) func)
                                       (funcall func s)))))))
      file-counts))
  
negative.code:     (do-audio-dir
        dir
        (lambda (s)
          (typecase s
            (id3:mp3-file
             (id3:map-id3-frames s
                                 :func (lambda (f)
                                         (insert-into-ht (id3:id f) m3-ht))))
            (m4a:mp4-file
             (m4a:map-mp4-atoms s
                                :func (lambda (f)
                                        (insert-into-ht (m4a:atom-type f) m4-ht)))))))
      (format t "MP3 Stats:~%")
      (loop for key being the hash-keys of m3-ht
            using (hash-value value)
  