SICP 問題 4.57

;; jiroの仕事をtaroができるかどうか
(rule (replacible ?person1 ?person2)
      (and (or (and (job ?person2 ?job2)
                    (job ?person1 ?job2)) ;person2とperosn1の仕事が同じ
               (and (job ?person1 ?job1)
                    (can-do-job ?job1 ?job2))) ;person1はperson2の仕事job2もできる
           (not (same ?person1 ?person2))))

;; a Cy D. Fectに代われる人すべて
(replacible ?person (Fect Cy D))

;; b
(and (salary ?person ?salary)
     (replacible ?person ?somebody)
     (salary ?somebody ?somebody-salary)
     (lisp-value > ?somebody-salary ?salary))