(defun chder (a b c cder n) (declare (type double-float a))
 (declare (type double-float b))
 (declare (type (simple-array double-float (*)) c))
 (declare (type (simple-array double-float (*)) cder))
 (declare (type fixnum n))
 (prog ((con 0.0d0) (j 0)) (declare (type double-float con))
  (declare (type fixnum j)) (fset (fref cder n) 0.0)
  (fset (fref cder (+ n (- 1))) (* (* 2 (+ n (- 1))) (fref c n)))
  (cond
   ((>= n 3)
    (fdo ((j (+ n (- 2)) (+ j (- 1)))) ((> j 1) nil)
     (tagbody
      (fset (fref cder j) (+ (fref cder (+ j 2)) (* (* 2 j) (fref c (+ j 1)))))
  ))))
  (setf con (/ 2.0 (+ b (- a))))
  (fdo ((j 1 (+ j 1))) ((> j n) nil)
   (tagbody (fset (fref cder j) (* (fref cder j) con)))
  )
  (return (values a b c cder n))
))