Helpful function for dealing with ring request maps?

apply_merge.clj

(defn ->merge [m & fns]
  "Merge the recursive result of calling f on m into m
  Useful when dealing with operations on ring request maps"
  (loop [m m
         fns fns]
    (if-not (seq fns)
      m
      (recur (merge m ((first fns) m)) (rest fns)))))

(assert (= {:a 1 :b 2}
           (->merge {:a 1} (fn [m] {:b 2})))) 

(assert (= {:a 1 :b 2 :k #{:a :b}}
           (->merge {:a 1} (fn [m] {:b 2}) (fn [m] {:k (set (keys m))}))))