Re: Multiple assignments to the same variable

Subject: Re: Multiple assignments to the same variable
From: Robert Raschke &lt;rtrlists@ ... &gt;
Date: Wed, 14 Jul 2010 11:18:47 +0100

On Wed, Jul 14, 2010 at 10:53 AM, Eike Decker <zet23t@googlemail.com> wrote:

2010/7/14 Martijn van Buul (Ellips B.V.) <martijn.van.buul@ellips.nl>:

>> -----Original Message-----
>> From: lua-bounces@bazar2.conectiva.com.br [mailto:lua-
>> bounces@bazar2.conectiva.com.br] On Behalf Of Petite Abeille
>> Sent: Tuesday, July 13, 2010 9:21 PM
>> To: Lua list
>> Subject: Re: Multiple assignments to the same variable
>>
>>
>> On Jul 13, 2010, at 8:34 PM, Romulo wrote:
>>
>> >> Usually we consider that what the manual does not say is undefined.
>> >
>> > Or overlooked.
>>
>> Same difference.
>
> Is that so? The manual doesn't say in what direction statements are
> executed; all it says that they are executed sequentially. I always
> thought that it was implied that they are executed top-to-bottom,
> left to right, but now I realize it is undefined behavior since this
> is not explicitly mentioned in the manual.
>
> I guess I should start writing palindrome-programs, just in case
> lua 6 decides to start executing in reverse.
>

This is very true... actually, if the assignment order on the left
side is undefined, the right side execution order is not helping if it
would be defined: If some metatables of the left side values are
calling functions because of the assignment, the program is already in
an "undefined" state.
I am not sure, but after pondering more and more on this issue, I come
to believe that the assignment order should be defined, both, left
side and right side order. Without such a statement, this could end up
in bugs that are hard to track down - and may end up in abolishing the
multiple assignment order at all.

Greetings,
Eike