api.clj

(defn filter-map
  "Returns map with items in m for which f returns true.
  f should take 2 arguments [key value]"
  [f m]
  (into {} (for [[k v] m :when (f k v)] [k v])))

(defn map-map
  "Returns map after applying f to key/values in m.
  f should take 2 arguments [key value] and return a sequence of 2 items [key' value']"
  [f m]
  (into {} (for [[k v] m] (f k v))))