Re: How do I add a "local" using the c api

[Mark Hamburg <mark@...>]

On Mar 31, 2009, at 8:15 AM, Tom Miles wrote:

> Urm, how to put this another way...
>
> When I create a state, I load an associated script file.  I want to  
> add
> some variables into the state the script is running in that are only
> visible to that script.  I can add globals using lua_setglobal(L,
> "myvar"), or even lua_setfield(L, LUA_GLOBALSINDEX, "myvar"), but  
> there
> doesn't seem to be an equivelant for locals.

Let me see if I've got the sequence right. You've got C code that  
loads a script and executes it to set up the environment. The C code  
needs to define some values that only that script should see rather  
than having them go into the global environment where they might be  
seen by other scripts.

Correct?

It isn't locals that you want because then they would only be visible  
to your script and not to the C code.

What you want is a custom environment for the script. So, do something  
like the following:

	load the script  -- you now have a compiled chunk on the top of the  
stack
	get the environment from the chunk (lua_getfenv) -- call the  
environment E for reference in what follows
	construct a table T= { } with metatable { __index = E, __newindex = E }
	put your special values into T
	set T as the environment for the chunk
	call the chunk

Now, there will be a set of global values visible only to the script  
but all other globals will still be visible and all globals created by  
the script will go into the main global environment.

Someone can remind me whether E is the same LUA_GLOBALSINDEX or  
LUA_ENVIRONINDEX. I forget which one it is which is why I copped out  
and got the environment from the chunk.

Mark