1 (defvar *dx* 0.00001)
2 (defun smooth (f)
3   (lambda (x)
4     (/ (+ (funcall f (- x *db*))
5 	  (funcall f x)
6 	  (funcall f (+ x *dx*)))
7        3)))
8 (defun n-fold-smooth (f n)
9   (funcall (repeated #'smooth n) f))