lisp - 第一个更大的(常见的)lisp 程序 -> 'random' 没有按预期工作

Question

只是为了好玩，我写了一个 "monty hall problem" 的模拟在 Python 中。后来用Lua试验了一下，决定用Lua再写一遍，看看对比一下会怎么样。这是一次非常有趣的体验，尽管程序看起来非常相似(Lua 版本略短)。最近我开始尝试使用 CL 并想再次做同样的事情。但是，当我运行它时，它的行为并不像预期的那样。由于某种原因，反复无常的玩家(应该有 66% 的获胜机会)与天真玩家(有 50% 的获胜机会)的得分几乎相同。

有人可以给我提示哪里出了问题吗？这不是家庭作业或类似的东西，只是我第一次尝试用 CL 编写更大的程序。除了有关上述问题的提示外，我还欢迎有关如何改进我的风格的建议。我猜它仍然很像 Python(它或多或少是直接翻译)。

(defun choose-one (l)
  "Ramdomly chooses one element of the given list"
  (nth (random (length l)) l))

(defun remove-one (l)
  "Randomly removes one element of the given list"
  (remove (choose-one l) l))

(defun naive-player (initial-choice possible-choices)
  "The naive player randomly picks one choice. Should have a 50% chance to win."
  initial-choice ;keep compiler happy
  (choose-one possible-choices))

(defun stubborn-player (initial-choice possible-choices)
  "The stubborn player sticks with his initial choice. Should have a 33% chance to win."
  possible-choices ;keep compiler happy
  initial-choice)

(defun erratic-player (initial-choice possible-choices)
  "The erratic player will always change his choice. Should have a 66% chance to win."
  (choose-one (remove initial-choice possible-choices)))

(defun host-offer (prize possible-choices)
  "The host reveals one wrong choice."
  (let ((remaining (remove prize possible-choices)))
    (remove (choose-one remaining) possible-choices)))

(defun one-game (playerfn choices)
  "Simulates a single game with the given player. Evaluates to T if the player won."
  (let ((prize (choose-one choices))
        (player-choice (choose-one choices)))
    (eq (funcall playerfn player-choice (host-offer prize choices)) prize)))


(defun multiple-games (num-games)
  "Simulates the given number of games with all players. Evaluates to a result list."
  (let ((choices '(door_a door_b door_c))
        (naive-score 0)
        (stubborn-score 0)
        (erratic-score 0))
    ;(progn
      (dotimes (i num-games)
        ;(progn
          (if (one-game #'naive-player choices)
              (incf naive-score))
          (if (one-game #'stubborn-player choices)
              (incf stubborn-score)) 
          (if (one-game #'erratic-player choices)
              (incf erratic-score)));)
      (list 
       (list 'naive-player naive-score) 
       (list 'stubborn-player stubborn-score)
       (list 'erratic-player erratic-score))));)

;; Run simulation and display results
(defparameter *num-games* 10000)
(format *standard-output* "--- Monty Hall ---~%")
(format *standard-output* "Simulating ~D games...~%" *num-games*)
(let ((result (multiple-games *num-games*)))
  (format *standard-output* "~{~{~A score: ~D~}~%~}" result))

输出(例如):

--- Monty Hall ---
Simulating 10000 games...
NAIVE-PLAYER score: 5014
STUBBORN-PLAYER score: 3333
ERRATIC-PLAYER score: 4968

Answer 1

主机报价功能错误。在定义的 Monty Hall 问题中，主机永远不会打开玩家选择的门，但您的程序没有考虑到这一点。如果问题得到解决，程序将返回预期结果。