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描述：
我有一个列表（名为 large-number-list），其中包含许多数字，我想得到这些数字的总和。
现在我将列表分成三个元素作为一组进行计算（该组将在代理的动作中计算），并将这三个元素的总和放入一个向量（命名为结果）。
最后，我将向量中的元素累积在一起。

代码如下： 

;use agent to calculate many number  
(def result (agent []))  
(def large-number-list [1 2 3 4 5 6 7 8 9 10 11 12]);assume that large-number-list contains many number in it   
(defn doin3 [col do-fn]  
    (let [[x1 x2 x3 & rest-elem]  col  
         rest-len (count rest-elem)]  
         (println "x1 x2 x3" x1 x2 x3)  
         (println "rest-len is " rest-len)  
         (do-fn x1 x2 x3)  
         (when (> rest-len 0) (doin3 rest-elem do-fn))))  
;assume that the calculate is a time-consumed operation  
(defn calculate [v x1 x2 x3]   
    (conj v (+ x1 x2 x3)))  
(doin3 large-number-list #(send result calculate %1 %2 %3))  
(println "before await")  
(await result)  
(println "after await")  
(println @result)  
(def total (apply + result))  
(println "total is:" total)  
(shutdown-agents)

预期输出： 

x1 x2 x3 1 2 3  
rest-len is  9  
x1 x2 x3 4 5 6  
rest-len is  6  
x1 x2 x3 7 8 9  
rest-len is  3  
x1 x2 x3 10 11 12  
rest-len is  0  
before await  
after await  
total is: 78

实际输出： 

x1 x2 x3 1 2 3  
rest-len is  9  
x1 x2 x3 4 5 6  
rest-len is  6  
x1 x2 x3 7 8 9  
rest-len is  3  
x1 x2 x3 10 11 12  
rest-len is  0  
before await

问题：
代码运行到“等待之前”并阻塞，我猜代理中的动作没有完成，但为什么呢？
请让我知道我的代码有什么问题？

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1 回答 1

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I think the problem is with this line:

(def total (apply + result))

It should be:

(def total (apply + @result))

It wasn't actually blocking, it was throwing an exception.

One more note: you should consider using recur in doin3, instead of direct call, as it's in a tail position already.

于 2013-08-19T08:02:54.537 回答