Question

我一直在使用Scheme中的一个简单的国际象棋程序，我定义的一个辅助函数消耗了一个片段，它的坐标（当前位置）并将它放在指定的坐标（此处移动到此处）上国际象棋棋盘，切换出任何位于Move-here坐标的棋子。该功能正如我所希望的那样工作，但现在无论出于何种原因，它已不再正常运行。我不知道是什么导致这种情况，并且已经跟踪并重新跟踪代码一段时间，现在试图找到错误。我希望有人能够了解情况。

以下是片段切换功能的代码，以及代码中使用的结构：

(define-struct place (row column piece))
;; Place is a structure (make-place r c p) where r is the rank of a piece
;; which is a symbol of 'Pawn, 'Rook, 'Knight, 'Bishop, 'King or 'Queen
;; and column and place. Together c and p give the placement coordinates,
;; where column is one symbol from '(a b c d e f g h) and row is a number from 
;; 1 - 8 inclusive.

(define-struct piece (rank color))
;; Piece is a structure (make-piece r col) where rank is as described for a place   structure, 
;; and colour is a symbo either 'black or 'white.

(define move-counter 1) ; Keeps track of the current number of mves made.
;; Odd indicates white to move, else black to move.

;; Swap-in: '(Symbol Symbol Nat) '(Symbol Nat) -> '(-2- void)
;; Conditions:
;;   Pre: Swap-in is '(rank column row) From is '(column row)
;;   Post: produces list of lists containing -2- and void. where void represents
;;         any changed values.
;; Purpose: Swap-piece is a helper for any X-Move function that dictates the legal
;;          moves of a given piece.

(define (swap-piece swap-in from)
  (map (λ (x)
         (map (λ (piece)
                (cond
                  [(and (= (third swap-in) (place-row piece)) 
                        (symbol=? (second swap-in) (place-column piece)))
                   (set-place-piece! piece 
                                     (make-piece (first swap-in) (cond
                                                                   [(odd? move-counter)     'white]
                                                                   [else 'black])))]
                  [(and (= (second from) (place-row piece))
                        (symbol=? (first from) (place-column piece)))
                   (set-place-piece! piece (make-piece empty empty))]
                  [else void]))
              x)) 
       board))

这是两个例子;第一个是它输出的，第二个是什么它应该输出（在这个例子中，Swap-piece有一个小的修改，因此它的一个参数是一个板，因为不使用我的棋盘上的整个数组）。

(define Example-board (list
                         (list
                          (make-place 8 'a (make-piece 'Rook 'black))
                          (make-place 7 'a (make-piece 'Pawn 'black)))
                         (list
                          (make-place 4 'a (make-piece 'Queen 'white))
                          (make-place 6 'b (make-piece 'King 'White))))) 

> (swap-piece '(Queen a 4) '(a 7) Example-board)
(shared ((-2- void)) (list (list -2- (void)) (list (void) -2-)))

所以我打电话给示例板来获取更新的电路板：

> Example-board
(list
 (list 
  (make-place 8 'a (make-piece 'Rook 'black)) 
  (make-place 7 'a (make-piece empty  empty)))
 (list 
  (make-place 4 'a (make-piece 'Queen 'white)) 
  (make-place 6 'b (make-piece 'King  'White))))

但是，我期望的输出是：

> Example-board
(list
 (list 
  (make-place 8 'a (make-piece 'Rook 'black)) 
  (make-place 7 'a (make-piece 'Queen 'white)))
 (list 
  (make-place 4 'a (make-piece empty empty)) 
  (make-place 6 'b (make-piece 'King  'White))))

对不起，对于长篇文章，但我无法弄清楚导致这种情况发生的原因。正如我所说，我确信这段代码在几个小时前就已经开始工作了。

编辑：我应该补充一点，我的交换功能中地图功能正在作用的列表，棋盘是棋盘。

Answer 1

我意识到导致错误放置/交换的原因是什么。我将交换部分向后移动，几乎肯定是因为我错误地标记了我的参数。我的代码基本上说：“如果我正在看的正方形的坐标等于我放置的棋子的坐标，请不要改变正方形”，这显然违背了移动棋子的目的。对于任何感兴趣的人，正确的代码是：

(define (swap-piece swap-in from)
  (map (λ (x)
         (map (λ (piece)
                (cond
                   ; comparing coordinates of current square to swap-in
                  [(and (= (third swap-in) (place-row piece)) 
                        (symbol=? (second swap-in) (place-column piece)))
                   ; If they are equal place, remove swap-in from that square
                   (set-place-piece! piece (make-piece empty empty))]
                   ; If the coordinates of the square equal the coordinates of From
                   ; place the swap-in piece there
                  [(and (= (second from) (place-row piece))
                        (symbol=? (first from) (place-column piece)))
                   (set-place-piece! piece 
                                     (make-piece (first swap-in) (cond
                                                                   [(odd? move-counter)  'white]
                                                                   [else 'black])))]
                  [else void]))
              x)) 
       board))

Scheme：将数组中的元素变换为国际象棋

1 个答案: