(define snlist-recur
  (lambda (flist fatom init)
    (letrec ([helper (lambda (l)
		       (cond [(null? l) init]
			     [(list? (car l))
			      (flist (helper (car l))
				     (helper (cdr l)))]
			     [else (fatom (car l)
					  (helper (cdr l)))]))])
      helper)))


(define last (snlist-recur (lambda (x y)
			     (if (null? y)
				 x
				 y))
			   (lambda (x y)
			     (if (null? y)
				 x
				 y))
			   '()))