anchor.diff:    (declare (type sparse-vector sparse-y)
              (type (simple-array double-float) dence-x result)
              (optimize (speed 3) (safety 0)))
  -  (loop for i fixnum from 0 to (1- (sparse-vector-length sparse-y)) do
  +  (dosvec sparse-y i
       (let ((dence-index (aref (sparse-vector-index-vector sparse-y) i)))
         (declare (type fixnum dence-index))
         (setf (aref result dence-index)
  
positive.code:   (declare (type sparse-vector sparse-y)
             (type (simple-array double-float) dence-x result)
             (optimize (speed 3) (safety 0)))
    (loop for i fixnum from 0 to (1- (sparse-vector-length sparse-y)) do
      (let ((dence-index (aref (sparse-vector-index-vector sparse-y) i)))
        (declare (type fixnum dence-index))
        (setf (aref result dence-index)
  
negative.code:            (type (simple-array double-float) result)
             (type double-float n)
             (optimize (speed 3) (safety 0)))
    (dosvec sparse-x i
      (let ((dence-index (aref (sparse-vector-index-vector sparse-x) i)))
        (declare (type fixnum dence-index))
        (setf (aref result dence-index)
  