Lua - Table Constructors

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Table is a versatile data structure in Lua and is used to create various types like array/dictionary or to create various data structures like stack, queue, linked list etc. A table can be in numerically indexed form or in a key-value pairs based associated form.

A table can be contructed in multiple ways. We'll cover most of the ways how to initialize a table in examples below−

Example - Using empty constructor

A table can be initialized as an empty table and then entries can be added later as required as shown below−

main.lua

-- empty table initialization using default constructor
numbers = {}

numbers[1] = 11
numbers[2] = 22
numbers[3] = 33

for k,v in pairs(numbers) do
   print(k, v)
end

Output

When the above code is built and executed, it produces the following result −

1	11
2	22
3	33

Example - Initialize associative table at time of creation

A assoicative table can be initialized at the time of creation as required as shown below−

main.lua

-- initialize table of fruits
fruits = {[2] = "banana",[4] = "orange",[6]="apple",[8] = "grapes"}

-- print the entries of table along with keys
for key,value in pairs(fruits) do
  print(key,value)
end

Output

When the above code is built and executed, it produces the following result −

8	grapes
2	banana
4	orange
6	apple

Example - Initialize numerically indexed table at time of creation

We can define a table without specifying the indexes as shown below−

main.lua

-- initialize table of numbers
numbers = {11, 22, 33, 44, 55, 66}

-- print the entries of table along with keys
for key,value in ipairs(numbers) do
  print(key,value)
end

Output

When the above code is built and executed, it produces the following result −

1	11
2	22
3	33
4	44
5	55
6	66

Example - Create Associative as well as numeric table

Following is an example where we've specified key-value as well as a numeric indexed array.

main.lua

-- initialize table of numbers
numbers = {[7] = 11, 22, 33, 44, 55, 66}

-- print the entries of table along with keys
for key,value in pairs(numbers) do
  print(key,value)
end

Output

When we run the above program, we will get the following output−

1	22
2	33
3	44
4	55
5	66
7	11

Example - Create Merged table

Following is an example where we've two tables separated by ;.

main.lua

-- initialize table of numbers
numbers = {[7] = 11; 22, 33, 44, 55, 66}

-- print the entries of table along with keys
for key,value in pairs(numbers) do
  print(key,value)
end

Output

When we run the above program, we will get the following output−

1	22
2	33
3	44
4	55
5	66
7	11