Re: Is it safe to unpack { nil, a, b } ?

[Niccolo Medici <niccolomedici@...>]

On 11/2/15, Andrew Starks <andrew.starks@trms.com> wrote:
> On Mon, Nov 2, 2015 at 12:32 AM, Niccolo Medici <niccolomedici@gmail.com>
>> [...] I need to wrap one of the system functions. Such
>> functions return (nil, errmsg, errcode) on error. So I have the
>> following pattern in my code:
>>
>>     local ret = { file:close() }
>>     -- do something
>>     return table.unpack(ret)
>> [...]
>
> I had the same issue and I did something similar. For me, this helped:
>
> ```
> local _unpack = table.unpack or unpack
> table.unpack = function(list, i, j)
>   return _unpack(list,i or 1, j or list.n or nil)
> end
> ```
>
> I understand that this does not *solve* your problem, 100%. For me,
> this works

Thanks, Andrew. That's helpful. I arrived at a very similar solution
that satisfies me 100%:

    function table.unpackx(t)
      return table.unpack(t, 1, t.n or table.maxn(t))
    end

(One also has to provide an implementation for maxn() because it was
deprecated after Lua 5.1.)