merge-with.clj

(defn deep-merge
  "Recursively merges maps. If vals are not maps, the last value wins."
  [& vals]
  (if (every? map? vals)
    (apply merge-with deep-merge vals)
    (last vals)))

(defn deep-merge-with
  "Like merge-with, but merges maps recursively, applying the given fn
  only when there's a non-map at a particular level."
  [f & maps]
  (apply
    (fn m [& maps]
      (if (every? map? maps)
        (apply merge-with m maps)
        (apply f maps)))
    maps))