clojure - 我如何用这个 Clojure 代码重写 (def)？

Question

我已经根据 deWitter's game loop 编写了一个游戏循环.

但是，我不确定如何将其转换为更具功能性的状态。我意识到代码中可能需要保留一些可变状态，但是是否有清理无关的 def 的一般原则？

(ns beepboop.core)

(def ticks-per-second 25)
(def skip-ticks (/ 1000 ticks-per-second))
(def max-frameskip 5)

(defn update []
  (println "Updating."))

(defn display [delta]
  (println "Displaying with delta: " delta))

(defn -main []
  (def *next-tick* (System/currentTimeMillis))
  (while true
    (def *loops* 0)
    (while (and
            (> (System/currentTimeMillis)
               *next-tick*)
            (< *loops*
               max-frameskip))
      (update)
      (def *next-tick* (+ *next-tick* skip-ticks))
      (def *loops* (+ *loops* 1)))
    (display
     (/ (+ (System/currentTimeMillis) skip-ticks (* -1 *next-tick*))
        skip-ticks))))

Answer 1

您应该使用loop 和recur 来更新您的循环变量:

(defn -main []
  (loop [next-tick (System/currentTimeMillis)]
    (let [next-next 
          (loop [next-tick next-tick
                 loops 0]
            (if (and (> (System/currentTimeMillis) next-tick)
                     (< loops max-frameskip))
                (do (update)
                    (recur (+ next-tick skip-ticks) (+ loops 1)))
                next-tick))]
      (display (/ (+ (System/currentTimeMillis) skip-ticks (- next-next))
                  skip-ticks))
      (recur next-next))))