方案中的3-堆Nim游戏

Question

我的代码不能正常工作，有人能指出我哪里出了错吗？提前谢谢。

下面是我的代码：

(define play-with-turns
  (lambda (game-state player)
    (display-game-state game-state)
    (cond ((over? game-state) 
           (announce-winner player))
          ((equal? player 'human)  
           (play-with-turns (human-move game-state) 'computer))
          ((equal? player 'computer)  
           (play-with-turns (computer-move game-state) 'human))
          (else  
           (error "player wasn't human or computer:" player)))))

(define computer-move
  (lambda (game-state)
    (let ((pile (if (> (size-of-pile game-state 1) 0)
                    1
                    2)))
      (display "I take 1 coin from pile ")
      (display pile)
      (newline)

      (remove-coins-from-pile game-state 1 pile))))

(define prompt
  (lambda (prompt-string)
    (newline)
    (display prompt-string)
    (newline)
    (read)))

(define human-move
  (lambda (game-state)
    (let ((p (prompt "Which pile will you remove from?")))
      (let ((n (prompt "How many coins do you want to remove?")))
        (remove-coins-from-pile game-state n p)))))

(define over?
  (lambda (game-state)
    (= (total-size game-state) 0)))

(define announce-winner
  (lambda (player)
    (if (equal? player 'human) 
        (display "You lose. Better luck next time.")
        (display "You win. Congratulations."))))

(define remove-coins-from-pile
  (lambda (game-state num-coins pile-number)
    (cond ((= pile-number 1)
           (make-game-state (- (size-of-pile game-state 1)
                               num-coins) 
                            (size-of-pile game-state 2)
                            (size-of-pile game-state 3)))
          ((= pile-number 2)
           (make-game-state (size-of-pile game-state 1)
                            (- (size-of-pile game-state 2)
                               num-coins)
                            (size-of-pile game-state 3)))
          ((= pile-number 3)
           (make-game-state (size-of-pile game-state 1)
                            (size-of-pile game-state 2)
                            (- (size-of-pile game-state 3)
                               num-coins))))))

(define exponent-of-in
  (lambda (n int)
    (if (= (remainder int n) 0)
        (+ 1 (exponent-of-in n (quotient int n)))
        0)))

(define make-game-state
  ;Returns a game state with n coins in the first pile
  ;m coins in the second pile, and k coins in the third pile.
  (lambda (n m k)
    (lambda (x)
      (cond ((= x 1) n)
            ((= x 2) m)
            ((= x 3) k)))))



(define size-of-pile
  ;Returns an integer equal to the number of coins in
  ;pile pile-number of the game-state.
  (lambda (game-state pile-number)
    (game-state pile-number)))

;; Utilities

(define display-game-state
  (lambda (game-state)
    (newline)
    (newline)
    (display "    Pile 1: ")
    (display (size-of-pile game-state 1))
    (newline)
    (display "    Pile 2: ")
    (display (size-of-pile game-state 2))
    (newline)
    (display "    Pile 3: ")
    (display (size-of-pile game-state 3))
    (newline)
    (newline)))

(define total-size
  (lambda (game-state)
    (+(+ (size-of-pile game-state 1)
         (size-of-pile game-state 2)) (size-of-pile game-state 3))))

示例输出：

(play-with-turns (make-game-state 5 9 8) 'human)


    Pile 1: 5
    Pile 2: 9
    Pile 3: 8


Which pile will you remove from?
1

How many coins do you want to remove?
2


    Pile 1: 4
    Pile 2: 9
    Pile 3: 8

I take 1 coin from pile 1


    Pile 1: 3
    Pile 2: 9
    Pile 3: 8


Which pile will you remove from?
2

How many coins do you want to remove?
2


    Pile 1: 2
    Pile 2: 7
    Pile 3: 8

I take 1 coin from pile 1


    Pile 1: 1
    Pile 2: 7
    Pile 3: 8


Which pile will you remove from?
2

How many coins do you want to remove?
2


    Pile 1: 1
    Pile 2: 5
    Pile 3: 8

I take 1 coin from pile 1


    Pile 1: 0
    Pile 2: 5
    Pile 3: 8

Answer 1

首先要做的是:我强烈建议您遵循中概述的设计食谱。首先，您的函数可以真正使用一行的目的语句。接下来，你真的真的需要这些函数的测试用例。我强烈怀疑您的remove-coins-from-pile函数有问题。

我在您的代码中发现了至少一个bug，您可以通过一组良好的测试用例轻松地捕获这些bug。如果你使用的是一种学生语言，你应该能够通过书写来测试，例如：

(check-expect ((remove-coins-from-pile (make-game-state 3 9 7) 5 2) 3) 172)

请注意，此测试用例实际上是错误的；您必须修复它。

如果您使用的是完整的#lang球拍语言，则需要添加

(require rackunit)

然后使用check-equal?进行测试：

(check-equal? ((remove-coins-from-pile (make-game-state 3 9 7) 5 2) 3) 172)

老实说，有人把你引向了一种基于函数的方法(游戏状态被表示为一个函数)，这使得测试比其他方法更加困难；如果你有一个“游戏状态”结构，你可以通过编写以下代码来一次性测试整个游戏状态，例如，

(check-equal? (remove-coins-from-pile (make-game-state 3 9 7) 5 2)
              (make-game-state 17 27 0))

我猜这是一位非常喜欢函数的讲师的作业。好吧，老实说，我真的很喜欢函数，但它们不适合在这种情况下进行测试。

有关更多详细信息，请再次参考“如何设计程序”文本。