问球拍中出现一个奇怪的错误：“一系列内部定义后没有表达式”

EN

(define (play-loop strat0 strat1 strat2 game-limit)
 (define (play-loop-iter strat0 strat1 strat2 count history0 history1 history2 limit)
  (cond ((= count limit) (print-out-results history0 history1 history2 limit))
      (else (let ((result0 (strat0 history0 history1 history2))
                  (result1 (strat1 history0 history1 history2)
                  (result2 (strat2 history0 history1 history2)))
              (play-loop-iter strat0 strat1 strat2 (+ 1 count)
                              (extend-history result0 history0)
                              (extend-history result1 history1)
                              (extend-history result2 history2)
                              limit)))))
 (play-loop-iter strat0 strat1 strat2 0 '() '() '() game-limit)))