anchor.diff:      (do-audio-dir
         dir
         (lambda (s)
  -        (cond ((typep s 'id3:mp3-file)
  -               (id3:map-id3-frames s
  -                                   :func (lambda (f)
  -                                           (insert-into-ht (id3:id f) m3-ht))))
  -              ((typep s 'm4a:mp4-file)
  -               (m4a:map-mp4-atoms s
  -                                  :func (lambda (f)
  -                                          (insert-into-ht (m4a:atom-type f) m4-ht)))))))
  +        (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)
  
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)))))))))
  
  
negative.code:                                (do-audio-file
                                   f
                                   (lambda (s)
                                     (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)))))))
      file-counts))
  