Clojure：此类型不支持第 n 个：布尔值”

Question

我正在尝试在 Clojure 中实现哲学家就餐示例。由于某些原因，我的程序总是死于异常

"java.lang.UnsupportedOperationException: nth not supported on this type: Boolean"

我无法理解此错误消息，因为我已经尝试从与 nth 完美配合的列表中获取布尔值

我猜错误发生在函数 philosopher-thread 中的 if 语句

控制台打印：

3正在思考
1 正在思考
4正在思考
0正在思考
2正在思考
0 睡后
0 思考后
0 交换
0 正在吃东西
3 睡后
三思后

代码：

(ns dining-philosphers.core
  (:gen-class))

(defn think [n] 
  (println (str n " is thinking"))
  (Thread/sleep (rand 1000))
  (println (str n " after sleep"))
)

(defn eat [n] 
  (println (str n " is eating"))
  (Thread/sleep (rand 1000))
)

(def isEating (atom '(false false false false false)))


(defn philosopher-thread [n] 
  (Thread. #( 
    (while true (do  
      (think n) 
      (println (str n " after think"))
      (if (or  (nth @isEating (mod (- n 1) 5))  (nth @isEating  (mod (+ n 1) 5)))
        (println "is waiting for neighbour")
        (
          do 
          (println (str n " swap"))
          (swap! isEating (fn [l] assoc l n true)) 
          (eat n)
          (swap! isEating (fn [l] assoc l n true))
        )
      )
     )
    ) 
  )

  )
)

(defn -main [& args] 
  (let [threads (map philosopher-thread (range 5))] 
    (doseq [thread threads] (.start thread))
    (doseq [thread threads] (.join thread))))

Answer 1

您在这里遗漏了一些括号：

(swap! isEating (fn [l] assoc l n true))

应该是

(swap! isEating (fn [l] (assoc l n true)))

第一个将按顺序计算assoc、l、n和true，return最后一个表达式的值（true)

还有一个问题，就是无法assoc上榜。我建议改用矢量：

(def isEating (atom [false false false false false]))

Clojure：此类型不支持第 n 个：布尔值”

Clojure: nth not supported on this type: Boolean"

clojure

clojure-java-interop