anchor.diff:    ((%replacer
       :type vector-replacer
       :initarg :replacer
  -    :reader read-replacer)
  -   (%mask-length
  -    :type (unsigned-byte 8)
  -    :initarg :mask-length
  -    :initform 32
  -    :reader read-mask-length)))
  +    :reader read-replacer)))
   
   
   @export
  
positive.code: 
  (defun apply-mask-to-index (index mask)
    (declare (type index index)
             (type (unsigned-byte 32) mask))
    (assert (< index 32))
    (logcount (ldb (byte index 0) mask)))
  
  
negative.code:     :reader read-container
      :initarg :container)
     (%mask
      :type (unsigned-byte 64)
      :initarg :mask
      :reader read-mask))
    (:documentation "Lookuptable that can hold up to 32 elements, under 32 indexes (from 0 to 31)."))
  