Moore machine macro

moore.clj

(ns machines.moore)

(defn make-state-fn [& states]
  (let [statemap
        (zipmap
          (map str states)
          (rest (conj (vec states) (first states))))]
    (fn [state] (statemap (str state)))))


(defmacro make-moore-machine
  [& states]
  `(let [state# (atom (first '~states))
         map#   (make-state-fn ~@states)]
      (fn [& _] (swap! state# map#))))


(def machine (make-moore-machine :stopped :starting :started :stopping))


;; all params are ignored
(machine "foobar" 123) ; :starting 
(machine)              ; :started
(machine)              ; :stopping
(machine)              ; :stopped