Re: rfc: array literals

Even though the behavior of "static" variables is semantically well
defined, it's true that this particular behavior is a bit confusing
(like the behavior of defvar which most people expect to work like
setq or defparameter).

The semantic of the code below is exactly like:

(defparameter some_random_name [0 0 0 0 0])
(defun test0 ()
   (for (i 0 3)
     (let ((v some_random_name))
       (v 0 (+ (v 0) 1))
       (printf "%f " (v 0)) ))
   (print) )

The proper way to fix this is to make array literal create a new
matrix every time, and return it.

  -- Yann


On Friday 12 December 2008, Ralf Juengling wrote:
> Hello,
>
> Consider this code, which exhibits a malicious bug.
>
> (defun test0 ()
>    (for (i 0 3)
>      (let ((v [0 0 0 0 0]))
>        (v 0 (+ (v 0) 1))
>        (printf "%f " (v 0)) ))
>    (print) )
>
> ? (test0)
> 1 2 3 4
> = ()
>
> The desired output is "1 1 1 1". If I remember correctly,
> somewhere in the documentation array literals are advertised
> as a means to simulate something like "static variables" in
> C. But here it does not square with the semantics of let.
>
> In my opinion, this is behavior will be confusing to many
> users and we should change it in Lush2. When compiled, v
> should simply be allocated on the stack when it is not returned
> (and dynamically otherwise).
>
> Ralf
>
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