(defmacro def-functorC
  [fn-name fn-arg body]
  (let [context (gensym)
        b (if (coll? body) body (list body))]
    `(defn ~fn-name [[~context ~fn-arg]]
       (list ~context ~(map #(if (= % :context) context %) b)))))

;;in its current form
(def-functorC my-fc
               arg
               arg)
;;fails since the "body" is just a single element

;but

(def-functorC  hello
                arg
  (reverse :context))

;;works since body is a collection