lambda - lambda 内部的非法函数调用

Question

我正在研究一个函数来计算国际象棋游戏中棋子的有效移动。 white-pawn-move 函数有效。当我试图将其概括为任一玩家的棋子 (pawn-move) 时，我遇到了非法函数调用。我已经在 repl 中测试了函数调用，但我认为这不是问题所在。

我做错了什么？

http://pastebin.com/fEiQTwi5

(defun white-pawn-move (file rank)       
  (let ((movelist '()))
    (if (and (within-boardp file (+ rank 1))
             (eql #\s (aref *board* (+ rank 1) file)))
        (push (cons file (+ rank 1)) movelist))
    (if (= rank 1) 
        (push (cons file (+ rank 2)) movelist))
    (if (and (within-boardp (- file 1) (+ rank 1))
             (belongs-to-opponent (aref *board*  (+ rank 1) (- file 1))))
        (push (cons (- file 1) (+ rank 1)) movelist))
    (if (and (within-boardp (+ file 1) (+ rank 1))
             (belongs-to-opponent (aref *board* (+ rank 1) (+ file 1))))
        (push (cons (+ file 1) (+ rank 1)) movelist))
    movelist))      

;refactor:
;file / rank numeric      
(defun pawn-move (direction)
  (let ((startrank (if (eql direction #'+)
                       1
                       6)))
    (lambda (file rank)
      (let ((movelist '()))
        (if (and (within-boardp file (funcall direction rank 1))
                 (eql #\s (aref *board* (funcall direction rank 1) file)))
            (push (cons file (funcall direction rank 1)) movelist))
        (if (= rank startrank) 
            (push (cons file (funcall direction rank 2)) movelist))
        (if (and (within-boardp (- file 1) (funcall direction rank 1))
                 (belongs-to-opponent (aref *board* 
                                            (funcall direction rank 1)
                                            (- file 1))))
            (push (cons (- file 1) (funcall direction rank 1)) movelist))
        (if (and (within-boardp (+ file 1) (funcall direction rank 1))
                 (belongs-to-opponent (aref *board*
                                            (funcall direction rank 1)
                                            (+ file 1))))
            (push (cons (+ file 1) (funcall direction rank 1)) movelist))
        movelist))))
;desired usage
(setf (gethash #\P *move-table*) (pawn-move #'+))    
(setf (gethash #\p *move-table*) (pawn-move #'-))

Answer 1

你能展示你得到的错误吗？

我刚刚使用 Emacs Lisp 尝试了您的代码(将字符表示更改为 Emacs-Lisp)，并且我没有收到 sexps (pawn-move #'+) 和 (典当移动#'-)。他们是什么引起了你的错误？我为 (pawn-move #'+) 得到这个，例如:

     (lambda (file rank)       (let ((movelist 'nil))         (if (and (within-boardp                   file                   (funcall direction rank 1))                  (eql 115                       (aref *board*                             (funcall direction rank 1)                             file)))             (push (cons file (funcall direction rank 1))                   movelist))         (if (= rank startrank)             (push (cons file (funcall direction rank 2))                   movelist))         (if (and (within-boardp                   (- file 1)                   (funcall direction rank 1))                  (belongs-to-opponent                   (aref *board* (funcall direction rank 1)                         (- file 1))))             (push (cons (- file 1) (funcall direction rank 1))                   movelist))         (if (and (within-boardp                   (+ file 1)                   (funcall direction rank 1))                  (belongs-to-opponent                   (aref *board*                         (funcall direction rank 1)                         (+ file 1))))             (push (cons (+ file 1) (funcall direction rank 1))                   movelist))         movelist))

总而言之，也许可以更详细地说明您所看到的内容。