Question

I’m trying to write a number guessing game in Lisp as a time-killing project. However, when I try to load up the program using SBCL, I get the following error:

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)

What does this error mean? The code is as follows, and the error appears when loading the file and calling (play) from the REPL:

;;;; 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)))

(I’m fairly certain that the program doesn’t work minus that one error, I’m still a complete novice when it comes to Lisp. This is just the first error I’ve encountered that I can’t figure out on my own.)

Oh, and the issue most likely has to do with the prompt-for-guess, read-guess and check-guess functions, because those were the ones I was messing with when this error cropped up.

Answer 1

It looks like you didn’t close enough parens on your prompt-for-guess defun.

The reader is getting to the end of the file and noticing that it has a form still open, and can’t figure out where it’s from.

An easy way I use to find errors like this is to have my text editor indent the region, and make sure everything lines up like I think it should.