(defun chebpc (c d n &key (nmax 50))
 (declare (type (simple-array double-float (*)) c))
 (declare (type (simple-array double-float (*)) d)) (declare (type fixnum n))
 (declare (type fixnum nmax))
 (prog
  ((dd (make-array '(nmax) :element-type 'double-float)) (sv 0.0d0) (k 0) (j 0)
  )
  (declare (type (simple-array double-float (*)) dd))
  (declare (type double-float sv)) (declare (type fixnum k))
  (declare (type fixnum j))
  (fdo ((j 1 (+ j 1))) ((> j n) nil)
   (tagbody (fset (fref d j) 0.0) (fset (fref dd j) 0.0))
  )
  (fset (fref d 1) (fref c n))
  (fdo ((j (+ n (- 1)) (+ j (- 1)))) ((> j 2) nil)
   (tagbody
    (fdo ((k (+ (+ n (- j)) 1) (+ k (- 1)))) ((> k 2) nil)
     (tagbody (setf sv (fref d k))
      (fset (fref d k) (+ (* 2.0 (fref d (+ k (- 1)))) (- (fref dd k))))
      (fset (fref dd k) sv)
    ))
    (setf sv (fref d 1)) (fset (fref d 1) (+ (- (fref dd 1)) (fref c j)))
    (fset (fref dd 1) sv)
  ))
  (fdo ((j n (+ j (- 1)))) ((> j 2) nil)
   (tagbody (fset (fref d j) (+ (fref d (+ j (- 1))) (- (fref dd j)))))
  )
  (fset (fref d 1) (+ (- (fref dd 1)) (* 0.5 (fref c 1))))
  (return (values c d n))
))