Clojure - 递归展平嵌套地图

Question

给定一个带有键的映射:content,其中content是字符串列表或其他映射,如何将值展平以仅接收字符串？

(flattener {:content '("b" {:content ("c" {:content ("d")})} "e")})

> '("b" "c" "d" "e")

我正在磕磕绊绊地进行非常粗暴的循环重复尝试,现在我的大脑被烧毁了.在Clojure中有一个很好的惯用方法吗？

谢谢.

我得到的是下面的,虽然它有效,但它很难看

(defn flatten-content
  [coll]
  (loop [acc '(), l coll]
    (let [fst (first l), rst (rest l)]
      (cond
       (empty? l) (reverse acc)
       (seq? fst) (recur acc (concat fst rst))
       (associative? fst) (recur acc (concat (:content fst) rst))
       :else (recur (conj acc fst) rst)))))

Answer 1

该tree-seq功能有助于步行,并且因为您的地图

(def m {:content '("b" {:content ("c" {:content ("d")})} "e")})

总是有一个"儿童"列表:content,这是有效的

(filter string? (tree-seq associative? :content m))
;=> ("b" "c" "d" "e")

Answer 2

以下递归函数有效(并且比filtered tree-seq方法快约25%):

(defn flatten-content [node]
  (lazy-seq
    (if (string? node)
      (list node)
      (mapcat flatten-content (:content node)))))