(defmacro data-ctor [name & args]
  `(defstruct ~name
     ~@(map (comp keyword str)
            (range (count args)))))

(defmacro type-ctor [name & ctors]
  `(do ~@(map (fn [ctor] (apply data-ctor ctor)) ctors)))

(type-ctor node
  (n2 :r :a :r)
  (n3 :r :a :r :a :r))