anchor.diff:    (when (hash-table-rehash-required hash-table)
       (hash-table-rehash hash-table 1))
     (do* ((free-slot nil)
  +        (size (hash-table-size hash-table))
  +        (test (hash-table-test hash-table))
  +        (storage (hash-table-storage hash-table))
   	;; This hash implementation is inspired by the Python dict implementation.
   	;; FIXME: Check if this really does hit all the entries in the table.
   	(slot (logand hash #xffffffff) (logand #xffffffff (+ (* slot 5) perturb 1)))
   	(perturb hash (ash perturb -5)))
          (nil)
  -    (let ((slot-key (hash-table-key-at hash-table (rem slot (hash-table-size hash-table)))))
  +    (let* ((offset (rem slot size))
  +           (slot-key (svref storage (ash offset 1)))) ; hash-table-key-at
         (when (and (null free-slot) (or (eql slot-key *hash-table-unbound-value*)
   				      (eql slot-key *hash-table-tombstone*)))
  -	(setf free-slot (rem slot (hash-table-size hash-table))))
  +	(setf free-slot offset))
         (when (eq slot-key *hash-table-unbound-value*)
   	;; Unbound value marks the end of this run.
   	(return (values nil free-slot)))
  -      (when (funcall (hash-table-test hash-table) key slot-key)
  -	(return (values (rem slot (hash-table-size hash-table)) free-slot))))))
  +      (when (funcall test key slot-key)
  +	(return (values offset free-slot))))))
   
   (defun hash-table-rehash (hash-table &optional (size-multiplier 3))
     "Resize and rehash HASH-TABLE so that there are no tombstones the usage
  
positive.code: 
  (defun (setf hash-table-value-at) (value hash-table index)
    (setf (svref (hash-table-storage hash-table) (1+ (* index 2))) value))
  
  (defun make-hash-table (&key (test 'eql) (size 101) (rehash-size 50) (rehash-threshold 1))
    ;; Canonicalize and check the test function
  
negative.code:   (storage (error "No storage provided.") :type simple-vector))
  
  (defun hash-table-size (hash-table)
    (ash (%simple-array-length (hash-table-storage hash-table)) -1))
  
  (defun hash-table-key-at (hash-table index)
    (svref (hash-table-storage hash-table) (* index 2)))
  