Lua Arrays

An array is a collection of elements of the same data type arranged in a certain order, which can be a one-dimensional array or a multidimensional array.

Lua array index keys can be represented by integers, and the size of the array is not fixed.

One-dimensional Arrays

One-dimensional arrays are the simplest arrays, with a logical structure of a linear table. One-dimensional arrays can iterate over the elements of the array using a for loop, as shown in the following example:

array = {"Lua", "Tutorial"}
for i= 0,　2　do
　　　print(array[i])
end

The output result of the above code is as follows:

nil
Lua
Tutorial

As you can see, we can use integer indices to access array elements, and if the known index has no value, it returns nil.

In Lua, index values are based on 1 as the starting point, but you can also specify starting from 0.

In addition, we can also use negative numbers as array index values:

array = {}
for i=　-2,　2　do
　　　array[i] = i　*2
end
for i =　-2,2　do
　　　print(array[i])
end

The output result of the above code is as follows:

-4
-2
0
2
4

Multidimensional Arrays

Multidimensional arrays are arrays that contain arrays or one-dimensional arrays, where the index keys correspond to an array.

Here is a three-row, three-column array of arrays:

--　Initialize the array
array = {}
for i=1,3　do
　　　array[i] = {}
　　　　　　for j=1,3　do
　　　　　　　　　array[i][j] = i*j
　　　　　　end
end
--　Access the array
for i=1,3　do
　　　for j=1,3　do
　　　　　　print(array[i][j])
　　　end
end

The output result of the above code is as follows:

1
2
3
2
4
6
3
6
9

A three-row, three-column array of arrays with different index keys:

--　Initialize the array
array = {}
maxRows =　3
maxColumns =　3
for row=1,maxRows do
　　　for col=1,maxColumns do
　　　　　　array[row*maxColumns　+col] = row*col
　　　end
end
--　Access the array
for row=1,maxRows do
　　　for col=1,maxColumns do
　　　　　　print(array[row*maxColumns　+col])
　　　end
end

The output result of the above code is as follows:

1
2
3
2
4
6
3
6
9

As you can see, in the above examples, the array is set to a specified index value to avoid nil values, which is beneficial for saving memory space.