(def data [{:a 1 :b 2} {:a 3 :b 4}])

(defn f [m]
  {:c (* 200 (:a m))})

(defn g [m]
  {:d (+ 2 (:b m))})

(defn h [m]
  {:e (- (:a m) (:b m))})

(defn lomm
  "let over map merge
   (lomm f g h data) => (let [f-xs (map f data)
                              g-xs (map g data)
                              h-xs (map h data)]
                          (map merge f-xs g-xs h-xs))

   Example:
   `(def data [{:a 1 :b 2} {:a 3 :b 4}])

    (defn f [m]
      {:c (* 200 (:a m))})

    (defn g [m]
      {:d (+ 2 (:b m))})

    (defn h [m]
      {:e (- (:a m) (:b m))})

    (lomm f g h data)
    ;; => ({:c 200, :d 4, :e -1} {:c 600, :d 6, :e -1})`"
  [& more]
  (let [data (last more)
        f-xs (butlast more)
        partial-xs (map #(map % data) f-xs)]
    (apply map merge partial-xs)))