recursion - 如何在 Clojure 中递归地展平任意嵌套的向量和映射？

Question

我正在尝试使用递归来遍历 Clojure 中任意嵌套向量和映射的树，并返回仅包含关键字(包括顶部)的向量。

因此应返回以下示例数据:

[:顶部:顶部:顶部:顶部:顶部:顶部:顶部:顶部:底部:底部:底部:底部:底部:底部:底部:底部:底部:底部:底部:底部],

但没有特定的顺序。

有人可以帮我正确地做到这一点吗？以下是我到目前为止所拥有的。

(def sample [{:top {:top {:top [:bottom {:top {:top [:bottom :bottom :bottom]}} :bottom :bottom :bottom]}}}, 
                        {:top {:top [:bottom :bottom :bottom]}}, 
                        {:top [:bottom :bottom]}])

(defn make-flat [graph]
  (loop [graph graph]
    (if (every? keyword? graph) graph
      (recur (into graph (flatten (seq (first (filter #(not (keyword? %)) graph)))))))))

(make-flat sample)

Answer 1

如果您的数据嵌套不是很深(例如向下数百层)，您可以简单地使用递归:

(defn my-flatten [x]
  (if (coll? x)
    (mapcat my-flatten x)
    [x]))

在回复中:

user> (my-flatten sample)
(:top :top :top :bottom :top :top :bottom :bottom :bottom 
 :bottom :bottom :bottom :top :top :bottom :bottom 
 :bottom :top :bottom :bottom)

否则我会同意tree-seq在这里是一个非常好的变体:

user> (filter keyword? (tree-seq coll? seq sample))
(:top :top :top :bottom :top :top :bottom :bottom 
 :bottom :bottom :bottom :bottom :top :top :bottom 
 :bottom :bottom :top :bottom :bottom)