anchor.diff:  
   (defun valid-layer (layer)
     (declare #.utils:*standard-optimize-settings*)
  -
  -  (or (= (the fixnum +layer-3+) (the fixnum layer))
  -      (= (the fixnum +layer-2+) (the fixnum layer))
  -      (= (the fixnum +layer-1+) (the fixnum layer))))
  +  (declare (fixnum layer))
  +
  +  (or (= +layer-3+ layer)
  +      (= +layer-2+ layer)
  +      (= +layer-1+ layer)))
   
   (defun get-layer-string (layer)
     (declare #.utils:*standard-optimize-settings*)
  -  (nth layer '("Reserved" "Layer III" "Layer II" "Layer I")))
  +  (declare (fixnum layer))
  +
  +  (aref #("Reserved" "Layer III" "Layer II" "Layer I") layer))
   
   ;;; the modes
  +(declaim (fixnum +channel-mode-stereo+
  +                 +channel-mode-joint+
  +                 +channel-mode-dual+
  +                 +channel-mode-mono+))
   (defconstant* +channel-mode-stereo+ 0)
   (defconstant* +channel-mode-joint+  1)
   (defconstant* +channel-mode-dual+   2)
  
positive.code: 
  (defun valid-sample-rate-index (sr-index)
    (declare #.utils:*standard-optimize-settings*)
  
    (and (>= (the fixnum sr-index) 0)
         (<  (the fixnum sr-index) 3)))
  
  (defun get-sample-rate (version sr-index)
    (declare #.utils:*standard-optimize-settings*)
  
negative.code:      ,@body))
  
  (let ((bit-array-table
         (make-array '(14 5)
                     :element-type 'fixnum
                     :initial-contents
                     '((32   32  32  32   8)
                       (64   48  40  48  16)
                       (96   56  48  56  24)
  