Re: Local Variables

[Tim Hill <drtimhill@...>]

On Aug 8, 2014, at 5:26 PM, William Ahern <william@25thandClement.com> wrote:

> On Fri, Aug 08, 2014 at 05:09:55PM -0700, Tim Hill wrote:
>> 
>> On Aug 8, 2014, at 3:29 PM, Mason Mackaman <masondeanm@aol.com> wrote:
>> 
>>> So why isn?t everything in the standard libraries made local by default if it?s always faster that way?
>> 
>> Because locals are not accessible to libraries (and should not be, that?s
>> what makes them local). A local ?foo? is fast because the compiler
>> converts accesses to it into direct references to the Lua stack.
> 
> It converts them into a fast index into an upvalue array stored as part of
> the currently running function.
> 
> The stack isn't involved at all, unless you create a closure which binds to
> a live function parameter. Then it copies the value from the stack to the
> upvalue slot when creating the function object.
> 
> 

I was simplifying for the OT. And last time I looked locals and upvalues were distinct.

—Tim