Re: In praise of globals

[Thomas Jericke <tjericke@...>]

That's pretty much what strict Lua does, and we do something similar as 
strict Lua (my version also lets you define constants).
But it's not what I wanted to suggest.

What I suggest is a change of the language. This means the parser would 
not allow LHS globals. You would catch this kind of error already at 
compile time, not at runtime. Errors at compile time are much, much 
better than provoking an error in the middle of a process. Our Lua 
scripts run real machines, it is really important that they run through.

> You can do this already.
>
> $ lua
> Lua 5.2.2  Copyright (C) 1994-2013 Lua.org, PUC-Rio
> > function assign(key,value) rawset(_G,key,value) end
> > setmetatable(_ENV,{__newindex =
>     function() error"Global LHS values are banned." end})
> > x=1
> stdin:2: Global LHS values are banned.
> stack traceback:
> 	[C]: in function 'error'
> 	stdin:2: in function '__newindex'
> 	stdin:1: in main chunk
> 	[C]: in ?
> > =x
> nil
> > assign('x',1)
> > =x
> 1

--

Thomas