Re: [Proposal] _LOCAL was: Re: how to call a local function by its name?

[Coda Highland <chighland@...>]

On Mon, Jun 8, 2015 at 2:09 PM, Soni L. <fakedme@gmail.com> wrote:
>
>
> On 08/06/15 06:05 PM, Soni L. wrote:
>
> I wish you could access your own locals with an _LOCAL[idx] that would be
> faster than debug.getlocal...
>
> Not sure how that'd work if you local x = _LOCAL, or called a function with
> _LOCAL...
>
> Actually I do know, _LOCAL tables would be like any other tables, but
> heavily optimized for this kind of stuff, and it'd be part of the function's
> call stack entry thingy. The GC can take care of the rest.

function locals()
return setmetatable({ [0]={} }, {
    __index = function(t, k)
            local ki = t[0][k]
            assert(ki, "attempt to read nonexistent local")
            local ln, lv = debug.getlocal(2, ki)
            assert(ln == k, "inconsistent state")
            return ln
        end,
    __newindex = function(t, k, v)
            local ki = t[0][k]
            if not ki then
                local i = 0
                while true do
                    i = i + 1
                    local ln, lv = debug.getlocal(2, i)
                    if ln == k then
                        ki = i
                        break
                    elif not ln then
                        break
                    end
                end
                assert(ki, "attempt to assign nonexistent local")
            end
            debug.setlocal(2, ki, v)
        end
})
end

_LOCAL = locals()

Untested... but that's about as good as you're going to get.

/s/ Adam