anchor.diff:  (defconstant upper-right-diagonals-list
     (reverse (mapcar #'reverse (mapcar #'reverse upper-left-diagonals-list))))
   
  +
   (make-precomputed-table upper-right-diagonals
   			upper-right-diagonals-list)
   
  
positive.code:   (reverse (mapcar (lambda (l) (reverse (mapcar #'reverse l))) 
  		   upper-left-diagonals-list)))
  
  (make-precomputed-table lower-left-diagonals
  			lower-left-diagonals-lsit)
  
  (make-precomputed-table clear-rank clear-rank-list)
negative.code: 
  (make-precomputed-table clear-file clear-file-list)
  
  (defconstant mask-rank-list
               (mapcar #'inverse clear-rank-list))
  
  