Re: Run a program

[Deniz Dogan <deniz@dogan.se>]

On 2011-09-27 07:28, Roland Thiers wrote:
> Hi all,
> I am a novice programming in Emacs Lisp.
> My question :
> I dit this program :
> (defun coins (n)
> (let ((i n) (repartition [0 0 0]) (c1 0) (c2 0) (r 0))
> (while (> i 0)
> (setq c1 (random 2))
> (setq c2 (random 2))
> (setq r (+ c1 c2))
> (aset repartition r (1+ (aref repartition r)))
> (setq i (- i 1)))
> (message " repartition %s " repartition)))
>
> aim : you toss two coins, count tails : 0 or 1 or 2. Repeat 10 times or
> more and see what happens.
>
> If I evaluate this program with C-x C-e and do (coins 10) C-x C-e it
> works fine, I get some thing like
> [3 5 2].
> But if I repeat C-x C-e after (coins 10) I get some thing like [5 11 4]
> then [9 15 6] ...
> I can't understand that !
> Could some one help me ?

I am not exactly sure why that happens, but it seems like you're 
referencing the same vector after each call.  To make sure the vector is 
fresh before each run, replace:

(repartition [0 0 0])

with:

(repartition (make-vector 3 0))