Re: Questioning variable scoping in Lua

[David Kastrup <dak@...>]

"Ben Aurel" <ben.aurel@gmail.com> writes:

> hi
> Because I'm new to Lua I'm going through some cool Lua projects (lqt,
> nanoki,...) in order to see how the language is used in real world
> projects.
>
> Even if you just look at the source from a distance, not necessarily
> trying to understand what the code actualy does, you notice the
> excessive use of the "local" keyword.
>
> - Setting the default scope to "global" why is that really usefull? I
> think most of the time, you try to avoid global state. Why not the
> default scope to "global"? Wouldn't that reduce a lot of typing?
>
> - What if the developer forgets a "local"? The program runs anyway,
> but there is a chance that there is some unwanted behavior that is
> hard to trace.
>
> I think I miss something here. Could somebody explain me the reason
> behind the design decision?

Lua is an interpreter, and if you use it in interpretive mode, each
chunk has its own scope:

> local y; y=3; y=y+1; print(y)
4
> print(y)
nil
> 

If the default was local, that would be inconvenient.  In particular
since function definitions are assignments as well.

-- 
David Kastrup