Re: Invalid key for "next" - Setting value nil while traversing

[Mitchell Hashimoto <mitchell.hashimoto@...>]

This is exactly the part in the manual I read and assumed it was for
just the scripting language, and not the C API, which I am using. But
since making the change to pushnil to pushinteger 0, it has fixed the
problem.

I'm still unsure why.

Mitchell

On Tue, Mar 3, 2009 at 5:57 AM, Roberto Ierusalimschy
<roberto@inf.puc-rio.br> wrote:
>> Now, I ask, should I not ever be setting a value to nil mid-traversal?
>> Why does this cause problems as I'm not modifying the key at all? My
>> initial assumptions were that some sort of GC was occuring before the
>> next iteration, which confused lua_next, since the value was GC'd
>> (nil). Is this correct?
>
> This should cause no problems. It is explicitly allowed:
>
>  * http://www.lua.org/manual/5.1/manual.html#pdf-next
>  The behavior of next is undefined if, during the traversal, you assign
>  any value to a non-existent field in the table. You may however modify
>  existing fields. In particular, you may clear existing fields.
>
> -- Roberto
>