Re: Let's talk about order of assignment

[Coda Highland <chighland@...>]

On Sun, Sep 14, 2014 at 1:44 PM, Hao Wu <wuhao.wise@gmail.com> wrote:
> On Sun, Sep 14, 2014 at 1:08 PM, Peter Melnichenko <mpeterval@gmail.com> wrote:
>> 14.09.2014 21:33 "Thiago L." <fakedme@gmail.com>:
>>
>>
>>>
>>> For example:
>>>
>>> Lua 5.2.3  Copyright (C) 1994-2013 Lua.org, PUC-Rio
>>> > setmetatable(_ENV, {__newindex = function(t,k,v) if k == "out" then
>>> > io.write(v) end end}) out,out,out = "what","the","fuck"
>>> fuckthewhat>
>>>
>>
>
> I am not sure this is right, but here is my thought:
>
>> More magic:
>>
>>> local a, a, a = 1, 2, 3; print(a)
>> 3
> In this case, the latter a is defined and overrode the previous one, thus used.
>
>>> b, b, b = 1, 2, 3; print(b)
>> 1
> the stack is popped in the reversed order so the first b is assigned
> lastly (the same as the OP's example)
>
> Another test I did kinda proved my theory:
>
>> local a = 1; function foo() a = a+1; return a; end;
>> local b,c,d = foo(), foo(), foo(); print(b,c,d)
> 2   3  4
>>local b,b,b=foo(),foo(),foo(); print(b)
> 7
>

As mentioned earlier in the thread: The behavior of ambiguous multiple
assignment is UNDEFINED. You can poke and speculate and figure out
what THIS version of Lua does, but you shouldn't rely on it. EVER.

It might change in the next version of Lua. It might be different in
third-party implementations of Lua. It might (however unlikely) change
if you build Lua on a different platform. It could fail entirely.

So it's a little silly to sit here and iterate on different possible
ways this might behave, because it's not required to be consistent (or
even sane).

/s/ Adam