(Random) in Common Lisp Not So Random?

问题:

Okay, final question and I'll have finished my number guessing game in Common Lisp! :D Whenever the game starts (or a new game begins after the first game), the following function is called.

;;; 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 (eql (prompt-for-guess) t)
        (play)
        (quit)))

So supposedly, each time the player starts a game, *target* should be set to a new random integer between 1-100. However, each time, *target* defaults to 82. How do I make (random) act... randomly?

回答1:

You need to seed the random state at the start of the program.

(setf *random-state* (make-random-state t))
;; # this initializes the global random state by
;;   "some means" (e.g. current time.)

回答2:

I think that if you define a function with a random number in it, it is not called when you call the function, actually, it will be determined when you load in the file and when it runs this definition it is fixed to that value. Then you are calling the function each time, the number will always be the same. When I passed in a variable to the function with a random each time it was called, then it was random each time. At least, that what I experienced in my program