lua中，重写for循环迭代器的不解之处。?报错

local function iter(a, i)
	print("**  iter >>> " .. i)
	i = i + 1
	local v = a[i]
	if v then
		return i, v
	end
end

function test(a)
	return iter, a, 0
end

local tab = {4, 5, 6}

for i,v in test(tab) do
	print("##   for >>> " .. i .. " = " .. v)
	print("\n")
end

return iter, a, 0

试过改成：

return iter（a, 0）

贴出的正常代码输出如下：

**  iter >>> 0
##   for >>> 1 = 4


**  iter >>> 1
##   for >>> 2 = 5


**  iter >>> 2
##   for >>> 3 = 6


**  iter >>> 3
[Finished in 0.4s]