不能将clojure.lang.LazySeq转换为clojure.lang.Associative类

Question

我对Clojure很陌生，我试着实现一种遗传算法。因此，我遇到了一个问题，实现一直抛出以下错误：

class clojure.lang.LazySeq cannot be cast to class clojure.lang.Associative (clojure.lang.LazySeq and clojure.lang.Associative are in unnamed module 
of loader 'app')

需要指出的是，每个函数都是在REPL中单独测试的，并返回正确的结果，但是在将它们放在一起之后，会抛出错误，而且我不理解它，因为它似乎没有指定行号。

clojure的版本是来自主分支的版本，是在Windows上用maven构建的。

完整的代码：

(ns ga)

(defn new-individual
    [genome-length]
    {:genome (vec (repeatedly genome-length #(rand-int 2))) :fitness 0}
    )


(defn fitness-function
    [genome, target]
    (Math/abs (- (reduce + genome) target))
)




(defn calculate-fitness
    [population, target]
    (defn fitness-function-helper 
        [individual, target]
        (assoc individual :fitness (fitness-function (individual :genome) target))
    )
        (map (fn [individual] (#(fitness-function-helper individual target))) population)
)



(defn crossover
        [first-individual, second-individual, crossover-rate, target]
        (let [new-genome (map (fn [i1,i2] (let [crossover-probability (rand)]
                                        (cond
                                            (<= crossover-probability crossover-rate) i1
                                            :else i2
                                        )
                                    )
                            ) 
            (first-individual :genome) (second-individual :genome)
                )]
            {:genome new-genome :fitness (fitness-function new-genome target)}
        )
        
)
        


(defn mutate
  [individual, genome-length, target]
  (let [new-genome (assoc (individual :genome) (rand-int genome-length) (rand-int 2))]
    {:genome new-genome :fitness (fitness-function new-genome target)}
  )
)



(defn better
  [i1 i2]
  (< (i1 :fitness) (i2 :fitness)))

(defn tournament-selection
  [population, population-size, steps, tournament-size, new-population, target]
  (if (< steps tournament-size)
    (recur population population-size (inc steps) tournament-size (conj new-population (nth population ((comp rand-int -) population-size 2))) target
      
     )
        ;(println new-population)
        (first (sort better (calculate-fitness new-population target)))
        
    )
)

(defn new-generation [population, population-size, crossover-rate, target, tournament-size]
    (loop [steps 0 new-population ()]
        (if (< steps population-size)
        (let [i1 (tournament-selection population population-size 0 tournament-size () target)]
            (let [i2 (tournament-selection population population-size 0 tournament-size () target)]
                (let [offs (crossover i1 i2 crossover-rate target)]
                    (recur (inc steps) (conj new-population offs))
                )
            )
        )
        new-population
    )
        )
    )
    
    (defn new-mutated-generation [population, population-size, genome-length, target]
        (loop [steps 0 new-population ()]
            (if (< steps population-size)
                    (recur (inc steps) (conj new-population (mutate (nth population steps) genome-length target)))
                    new-population
            )

        )

    )
        

(defn evolve [population-size, genome-length, target]
(let [population (calculate-fitness (repeatedly population-size #(new-individual genome-length)) target)]
    (let [offsprings (new-generation population population-size 0.5 target 5)]
        (println (new-mutated-generation offsprings population-size genome-length target))
        )
    


)

)

(evolve 10 5 5)

Answer 1

堆栈跟踪显示，有问题的代码是行

(let [new-genome (assoc (vec (individual :genome)) (rand-int genome-length) (rand-int 2))]

更具体地说，对assoc的调用。如果我们在上面插入以下行来编辑代码：

(println "Individual: " (individual :genome) ", " (class (individual :genome)))

印出来

Individual:  (0 1 1 0 1) ,  clojure.lang.LazySeq

问题是assoc不能与惰性序列(clojure.lang.LazySeq)一起使用，因为它没有实现阿索克需要的clojure.lang.Associative接口。

这个延迟序列是通过对该行上的map的调用来构造的：

(let [new-genome (map (fn [i1,i2] (let [crossover-probability (rand)]

如果将地图替换为马普夫，则代码如下所示

(let [new-genome (mapv (fn [i1,i2] (let [crossover-probability (rand)]

密码会有效的。

Answer 2

错误发生在函数mutate中。它有以下消息来源：

(defn mutate
  [individual, genome-length, target]
  (let [new-genome (assoc (individual :genome) (rand-int genome-length) (rand-int 2))]
    {:genome new-genome :fitness (fitness-function new-genome target)}))

在一个步骤中，您使用以下参数调用它：{:genome (0 1 1 1 1), :fitness 1} 5 5 (基因组可能有不同的价值，但它总是数字序列)。

(individual :genome)返回(0 1 1 1 1) (序列)，然后使用assoc，它是哈希映射或向量的函数。

基因组最初是载体，但在crossover函数中被转换成序列--在这里使用mapv而不是map：

(defn crossover
  [first-individual, second-individual, crossover-rate, target]
  (let [new-genome (mapv (fn [i1, i2] (let [crossover-probability (rand)]
                                        (if (<= crossover-probability crossover-rate) i1 i2)))
                         (first-individual :genome) (second-individual :genome))]
    {:genome new-genome :fitness (fitness-function new-genome target)}))

顺便说一下，定义末尾的所有括号都属于同一行。