How to Collapse Nested Map into a Sequence of Flat Maps

[Ari King]

How I can collapse a nested map with "n" number of keys (tiers) to create a sequence of flat maps which are comprised of composite keys and a values.

For example, let's say we have:

 {"a" {2011 [["a" 2011 "ari"] ["a" 2011 "dan"]], 2010 [["a" 2010 "jon"]]}} 

I'd like to collapse the nest into a sequence of flat maps like:

( { [a 2011] [ ["a" 2011 "ari"] ["a" 2011 "dan"] ] } , { [a 2010] [ ["a" 2010 "jon"] ] } ) 

[Ari King]

I've put together a solution (see below) that collapses nested maps into a sequence of flat maps with composite keys. Unfortunately, the solution wraps the result within another list, anyone know why? Thanks.

(defn collapse [data & keys-coll]
  (if (map? data)
    (for [[k v] data]
      (collapse v (if (nil? keys-coll)
                    (conj [] k)
                    (conj (into [] keys-coll) k))))
  (hash-map (flatten keys-coll) data)))