local new, del
do
	local list = setmetatable({}, {__mode='k'})
	function new()
		local t = next(list)
		if t then
			list[t] = nil
			return t
		else
			return {}
		end
	end

	function del(t)
		setmetatable(t, nil)
		for k in pairs(t) do
			t[k] = nil
		end
		table.setn(t, 0)
		list[t] = true
	end
end