Lua table insertion by reference

Question

I want to add to a table a variable and see the changes made in table in the single variable. I think that the problem ocurrs because when i insert the variable to the table it's passed by value.

Now I set to nil one element in the table but the variable that i want asssociate it's not modified. How I can associate the values to achieve that the next program prints "is nil" and not "is not nil".

tab = {}

x = 2
y = 4

table.insert(tab, x)
table.insert(tab, y)

for i = 1 , #tab do
    tab[i] = nil
end

if x == nil then print("is nil")
else  print("is not nil") end

SOLVED:

This is the solution. Convert the variables to tables. The problem is that the sintax becomes ugly because of the [1] index. I will see if I can hide this because i will be using a lot in my scripts this variables and I don't want to be using all the time the [] index for only one variable.

tab = {}

x = {2}
y = {4}

table.insert(tab, x)
table.insert(tab, y)


for i = 1 , #tab do
    tab[i][1] = nil
end

if x[1] == nil then print("is nil")
else  print("is not nil") end

Answer 1

You can't do this in lua. Not this way. The only things that have reference semantics are tables and userdata.

If you were assigning a table into tab then modifying fields of that table would be visible from the original variable and from tab.