Re: tostring() and the "not even nil" type.

[WU Jun <quark@...>]

In lua source code, there is a LUA_TNONE type.
It is different from LUA_TNIL.

LUA_TNONE is useful in C API, when trying to get a value type exceeding 
a valid stack range, LUA_TNONE is got.

I think tostring() can regard LUA_TNONE as LUA_TNIL.

On 04/30/2010 03:31 AM, Pierre-Yves Gérardy wrote:
> > a=function()end
> > = tostring(a()) -->  Error.
> > = tostring(select(2)) -->  Ditto.
>
> tostring() throws an error when it doesn't receive any argument. Since
> it is often called to sanitize a result before concatenation, it could
> make sense if it returned "nil", or even the empty string instead.
>
> In most other circumstances, these "lack of value" are converted to
> nil, but not here.
>
> A partial solution is to append "or nil" to the argument of every
> risky tostring() call, but it would be more elegant if it were handled
> at the language level.
>
> -- Pierre-Yves