anchor.diff:  
   ;; (compute-array-vector* #3A(((1 2 3 4) (4 3 2 1)) ((4 3 2 1) (1 2 3 4))))
   ;; => #(#(#(1 2 3 4) #(4 3 2 1)) #(#(4 3 2 1) #(1 2 3 4)))
  +
  +;; (compute-array-vector* #2A())
  +;; => #()
   
   (defun row (m i)
     (declare (type array-dimension-designator i)
  
positive.code:   (declare (type array m)
             (values (simple-array * (*))))
    (let ((dims (array-dimensions m)))
      (labels ((frob (m dims &optional upper-offsets)
                 (let ((this-dim (car dims))
                       (rest-dim (cdr dims)))
                   (cond 
  
negative.code:                         (setf (aref retv n)
                                (row-major-aref 
                                 m  
                                 (* upper-offset n))))))))))
        (frob m dims))))
  
  ;; (compute-array-vector* #2A((1 2 3 4) (4 3 2 1)))
  