avoid table lookups?

[spir <denis.spir@...>]

Hello,

Is it worth in Lua, at start of a func or before a loop, to "localise" table 
fields? As in:

f = function (t)
   local x = t.x
   if x < 0 then
      ... use x ...
   else
      ... use x ...
   end
   ...
   local z = t.y.z
   for i = 1, 1000 do
      ... use z ...
   end
   ...
end

Thank you,
Denis