How can I get the nested keys of a map in clojure?

Question

if my structure is

{ :a :A
  :b :B
  :c {
       :d :D
     }
  :e {
       :f {
            :g :G
            :h :H
          }
     }
}

I

Answer 1

Here is an implementation which returns all keys (not just the terminal keys) based on lazy-seq:

(defn keys-in
  ([m] (if (map? m) (keys-in (seq m) [])))
  ([es c]
   (lazy-seq
    (when-let [e (first es)]
      (let [c* (conj c (key e))]
        (cons c* (concat (if (map? (val e)) (keys-in (seq (val e)) c*))
                         (keys-in (rest es) c))))))))