;; <regent> := (general aide)
;;    where general is a knight, and aide is a serf.
;; 
;; <knight> := (private salary)
;;             | (officer fellow squire servant salary)
;;    where fellow is a knight, and squire and servant are serfs.
;;    salary is a number of potatoes.
;; 
;; <serf> := (simpleton potatoes)
;;           | (idiot)
;;           | (spy rebel)
;;    where potatoes is a number, and rebel is a regent.


;; Template for knight:
;;
(define knight-fun
  (lambda (k)
    (cond [(knight-private? k)
           ...(knight-private-salary k)...]
          [(knight-officer? k)
           ...(knight-officer-fellow k)...(knight-officer-squire k)...
           ...(knight-officer-servant k)...(knight-officer-salary k)...]
          [else (error 'knight-fun "Bad knight ~s" k)])))