Re: nil's metatable

[David Jones <drj@...>]

On 4 Jul 2006, at 17:17, Mike Pall wrote:

> Hi,
>
> David Jones wrote:
> > Now, I don't really have an excuse for poking around in this dark
> > corner, but...
> > is this intended?
>
> Probably not. But it's not really a bug either. It could be
> called a leak in the implementation.
>
> It's a side-effect of common code for unary and binary operators
> in lvm.c and an assumption that nil never has metamethods:
>
>   case OP_LEN:
>     ...
>     if (!call_binTM(L, rb, luaO_nilobject, ra, TM_LEN)) ...
>
> If the 1st operand (a function in your case) has no metamethod
> then call_binTM goes on to try the 2nd operand ... which is nil.
> By default nil does not have any metamethods, so you get the
> expected error, even for unary operators.

I know.  You don't think I found it by accident do you?  I was poking  
around in the source.
> So you have to remember to set metamethods for all other types in
> case you really want to use metamethods for nil. I'm not sure
> this is a good idea, anyway. :-)

No, I'm not sure it is either.

drj