Finding the path of a node in a tree.

nested_map_value_path.clj

(defn map-zip [m]
  (clojure.zip/zipper #(or (map? %) (map? (nth % 1)))
                      #(seq (if (map? %) % (nth % 1)))
                      (fn [x children]
                        (if (map? x)
                          (into {} children)
                          (assoc x 1 (into {} children))))
                      m))

(defn path [m value]
  (loop [current-location (map-zip m)]
    (let [current-node (clojure.zip/node current-location)
          current-path (clojure.zip/path current-location)]
      (if (= (last current-node) value)
        (conj (into [] (rest (map first current-path)))
              (first (first current-location)))
        (if (clojure.zip/end? current-location)
          nil
          (recur (clojure.zip/next current-location)))))))

(path {:a 1
       :b {:c 2
           :d {:e 3
               :f 4
               :g {:h 5}}}}
      5)
;; => [:b :d :g :h]