Passing a table as an array

Keys of a table can be consecutive integers, starting at 1. They can be made into an array (or a list):

colors =  {
[1] = "Green", 
[2] = "Blue", 
[3] = "Yellow", 
[4] = "Orange", 
[5] = "Red"
}
print(colors[4]) -- Orange

Another way of writing table constructors to build arrays in a faster and more convenient way that doesn't require writing out each integer key is shown here:

colors = {"Green", "Blue", "Yellow", "Orange", "Red"}
print(colors[4]) -- Orange

Altering contents in a table

While working with tables, you can modify or remove the values already in it and also add new values to it. This can be accomplished using the assignment statement. The following example creates a table with three people and their favorite types of drink. You can make an assignment to change one person's drink, add a new person-drink pair to the table, and remove an existing person-drink pair:

drinks = {Jim = "orange juice", Matt = "soda", Jackie = "milk"}
drinks.Jackie = "lemonade" -- A change.
drinks.Anne = "water" -- An addition.
drinks.Jim = nil -- A removal.

print(drinks.Jackie, drinks.Anne, drinks.Matt, drinks.Jim)
-- lemonade water soda nil

drinks.Jackie = "lemonade" overwrites the original value of drinks.Jackie = "milk".

drinks.Anne = "water" adds a new key and value to the table. The value of drinks.Anne before this line would have been nil.

The value of drinks.Matt = "soda" stays the same since there were no alterations to it.

drinks.Jim = nil overwrites the original value of drinks.Jim = "orange juice" with nil. It removes the Jim key from the table.

Populating a table

Ways to populate a table is to start with an empty table and add things to it one at a time. We'll use constructors, which are expressions that create and initialize tables. The simplest constructor is the empty constructor, {}:

myNumbers = {} -- Empty table constructor

for i = 1, 5 do
  myNumbers[i] = i 
end

for i = 1, 5 do
print("This is number " .. myNumbers[i])
end

The following are the results from the terminal:

--This is number 1
--This is number 2
--This is number 3
--This is number 4
--This is number 5

The preceding example shows that myNumbers = {} is an empty table constructor. A for loop is created and calls myNumbers[i] 5 times, starting from number 1. Each time it is called, it is incremented by 1 and then printed out.