;;;; match over an enum: the arms name members as keywords, a _ arm is the
;;;; rest, and a match that names neither every member nor _ is refused.

(defenum Dir [north east south west])

(defn turn [d Dir] Dir
  (match d
    :north :east
    :east  :south
    :south :west
    :west  :north))

(defn name [d Dir] string
  (match d
    :north "north"
    :south "south"
    _      "sideways"))

(defn calls [] i32
  (print "(called) ")
  0)

;; The scrutinee is evaluated once, however many arms test it.
(defn once [] Dir
  (calls)
  :west)

;; recur from inside an arm: the arm is the loop's tail.
(defn steps-to-west [from Dir] i32
  (loop [d from  n 0]
    (match d
      :west n
      _     (recur (turn d) (+ n 1)))))

(defn main [] i32
  (print (steps-to-west :north)) (println "")
  (println (name :north))
  (println (name (turn :north)))
  (println (name (turn (turn :north))))
  (println (name (once)))
  (match (turn :west)
    :north (println "back to north")
    _      (println "somewhere else"))
  0)