Common Lisp 错误无法理解

Question

我正在尝试用 Lisp 编写一个猜数字游戏作为一个消磨时间的项目。但是，当我尝试使用 SBCL 加载程序时，出现以下错误：

debugger invoked on a SB-C::INPUT-ERROR-IN-COMPILE-FILE in thread #<THREAD
                                                                    "initial thread" RUNNING
                                                                    {AA14959}>:
  READ failure in COMPILE-FILE at character 477:
    end of file on #<SB-SYS:FD-STREAM
                     for "file /home/andy/Dropbox/Programming/Common Lisp/number-game.lisp"
                     {B4F45F9}>

Type HELP for debugger help, or (SB-EXT:QUIT) to exit from SBCL.

restarts (invokable by number or by possibly-abbreviated name):
  0: [CONTINUE] Ignore runtime option --load "number-game.lisp".
  1: [ABORT   ] Skip rest of --eval and --load options.
  2:            Skip to toplevel READ/EVAL/PRINT loop.
  3: [QUIT    ] Quit SBCL (calling #'QUIT, killing the process).

(SB-C::READ-FOR-COMPILE-FILE
 #<SB-SYS:FD-STREAM
   for "file /home/andy/Dropbox/Programming/Common Lisp/number-game.lisp"
   {B4F45F9}>
 477)

此错误是什么意思？代码如下，加载文件并从 REPL 调用 (play) 时出现错误：（

;;;; number-game.lisp
;;;;
;;;; Andrew Levenson
;;;; 10/25/2010
;;;;
;;;; Simple number guessing game. User has
;;;; five guesses to determine a number between
;;;; one and one hundred, inclusive (1-100).

;;; Set global variable for the target number:
(defparameter *target* nil) 

;;; Set the iterator so we may check the number of guesses
(defparameter *number-of-guesses* 0)

;;; Welcome the user
(defun welcome-user ()
    (format t "Welcome to the number guessing game!~%"))

;;; Prompt for a guess
(defun prompt-for-guess ()
    (format t "Please enter your guess (1-100): ")
    (finish-output nil) ; nil directs finish-output to standard IO
    (check-guess((read-guess)))

;;; Read in a guess
(defun read-guess ()
    (let ((guess (read)))
        (if (numberp guess) ; If true, return guess. Else, call prompt-for-guess
            (progn
                (setq *number-of-guesses* (+ *number-of-guesses* 1))
                guess)
            (prompt-for-guess))))

;;; Check if the guess is higher than, lower than, or equal to, the target
(defun check-guess (guess)
    (if (equal guess *target*)
        (equal-to)
        (if (> guess *target*)
            (greater-than (guess))
            (if (< guess *target*)
                (less-than (guess))))))

;;; If the guess is equal to the target, the game is over
(defun equal-to ()
    (format t "Congratulations! You have guessed the target number, ~a!~%" *target*)
    (y-or-n-p "Play again? [y/n] "))

;;; If the guess is greater than the target, inform the player.
(defun greater-than (guess)
    (format t "Sorry, ~a is greater than the target.~%" guess)
    (if (< *number-of-guesses* 6)
        (prompt-for-guess)
        (game-over)))

;;; If the guess is less than the target, inform the player.
(defun less-than (guess)
    (format t "Sorry, ~a is less than the target.~%" guess)
    (if (< *number-of-guesses* 6)
        (prompt-for-guess)
        (game-over)))

;;; If the player has run out of guesses, give them the option
;;; of playing the game again.
(defun game-over ()
    (y-or-n-p "You have run out of guesses. Play again? [y/n] "))


;;; Play the game
(defun play ()
    ;; If it's their first time playing this session,
    ;; make sure to greet the user.
    (unless (> *number-of-guesses* 0)
        (welcome-user))
    ;; Reset their remaining guesses
    (setq *number-of-guesses* 0)
    ;; Set the target value
    (setq *target*
        ;; Random can return float values,
        ;; so we must round the result to get
        ;; an integer value.
        (round
            ;; Add one to the result, because
            ;; (random 100) yields a number between
            ;; 0 and 99, whereas we want a number
            ;; from 1 to 100 inclusive.
            (+ (random 100) 1)))
    (if (equal (prompt-for-guess) "y")
        (play)
        (quit)))

我相当肯定，除了那个错误之外，程序无法工作，我'对于 Lisp 来说，我还是一个完全的新手。这只是我遇到的第一个我自己无法解决的错误。）

哦，这个问题很可能与提示有关 - for-guess、read-guess 和 check-guess 函数，因为当这个错误出现时，我正在处理这些函数。

Answer 1

看来您在 prompt-for-guess defun 上没有关闭足够的括号。

读者正在读到文件的末尾，并注意到它有一个仍然打开的表单，并且无法弄清楚它来自哪里。

我用来查找此类错误的一个简单方法是让我的文本编辑器缩进该区域，并确保所有内容都按照我的想法排列。

Answer 2

Emacs 中的命令是 Mx check-parens（它检查需要平衡的所有内容，例如引号）。如果一切都平衡，这可能会有点令人困惑，因为在这种情况下它什么也不做。

检查括号
命令：检查当前缓冲区中是否有不平衡的括号。
更准确地说，检查缓冲区变窄的部分是否不平衡
一般表达式（“sexps”）。这是根据
当前语法表，会发现不平衡的括号或引号
合适的。 （请参阅信息节点“(emacs)Parentheses”。）如果不平衡是
发现，发出错误信号，并将点留在第一个不平衡处
特点。

Answer 3

读取期间的文件结尾，缺少右括号（或类似的）。字符 477。将文本中的光标移到 477 并检查它是哪个表达式。

检查 IDE 中是否有命令来查找不平衡的表达式。

在 LispWorks 中，这将是 Mx Find Unbalanced Parentheses。

SLIME 也应该有一些命令。