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On 08/06/15 07:24 PM, Coda Highland wrote:

On Mon, Jun 8, 2015 at 3:14 PM, Soni L. <fakedme@gmail.com> wrote:


On 08/06/15 06:40 PM, Coda Highland wrote:

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


Not faster than debug.getlocal, cannot be passed around, cannot be indexed
with NUMBERS, doesn't give access to varargs... What else? (I guess the
varargs part would be really awesome tbh, just changing varargs on the fly,
accessing them at 0 (or at least little) cost, etc... Can debug.setlocal()
be used to set varargs?)


I started working on that before you sent the e-mail with the extra
constraints on it.

Adding indexing by numbers would be near-trivially easy -- in fact I
was GOING to do that before I realized it wasn't necessary and would
just add overhead. And indexing by numbers would trivially enable
varargs.

I MIGHT be able to optimize matters a little bit further if I can
memoize _LOCAL across function invocations, but that could potentially
be fragile; there's research I'd have to do first.

Regardless, asking for better performance out of this is rather silly
-- when would you EVER be in a situation where you're not implementing
a debugger and reflection is the only answer you can come up with for
how to do something?

/s/ Adam


Python has it.

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