Re: Controlling scoping

[Peter Hickman <peterhi@...>]

Kevin Baca wrote:

> I'm not sure why that's working for you.
>
> What you want is called a "sandbox".  Search the archives for "sandbox"
> for some interesting discussions.
>
> Here is a simple example:
>
>  
>
> > s1 = "x = 42"
> > c1 = loadstring( s1 )
> > e = setmetatable( {}, { __index = __G } )
> > setfenv( c1, e )
> > c1()
> > =x
> >    
> nil
>  
>
> > =e.x
> >    
> 42
>
> -Kevin
>  
I must have been seeing things because now I am back home the code 
doesn't work? However your code does, however I for me I used a single 
underscore _G but your code used a double __G. The double did not work 
for me.

#!/usr/local/bin/lua

function compilestring( s )
       e = setmetatable( {}, { __index = _G } )
       c = loadstring( s )
       setfenv( c, e )
       return c
end

c1 = compilestring( "print(x)" )
c2 = compilestring( "x = 42" )
c3 = compilestring( "x = 19 print(x)" )

c1()
c2()
c1()
c3()
c1()

[Lua]$ ./x.lua
nil
nil
19
nil
[Lua]$

getting better, thanks for your help.