clojure - Iterate over all keys of nested map

Question

Given:

{:o {:i1 1
     :i2 {:ii1 4}}}

I'd like to iterate over the keys of the map in "absolute" form from the root as a vector. So I'd like:

{
 [:o :i1] 1
 [:o :i2 :ii1] 4
}

As the result. Basically only get the leaf nodes.

Answer 1

A version that I think is rather nicer, using for instead of mapcat:

(defn flatten-keys [m]
  (if (not (map? m))
    {[] m}
    (into {}
          (for [[k v] m
                [ks v'] (flatten-keys v)]
            [(cons k ks) v']))))

The function is naturally recursive, and the most convenient base case for a non-map is "this one value, with no keyseq leading to it". For a map, you can just call flatten-keys on each value in the map, and prepend its key to each keyseq of the resulting map.