4.20. Lua array

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

The index key value of an Lua array can be expressed as an integer, and the size of the array is not fixed.

4.20.1. One-dimensional array #

One-dimensional array is the simplest array, and its logical structure is linear table. An one-dimensional array can be used for loop out the elements in the array, as an example:

Example #

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

The output of the above code execution is as follows:

nil
Lua
Tutorial

As you can see, we can use an integer index to access the array elements andreturn if the known index has no value nil .

In Lua index value starts with 1, but you can also specify 0 to start.

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

Example #

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

The output of the above code execution is as follows:

4.20.2. Multidimensional array #

A multi-dimensional array is an array corresponding to the index key of an array that contains an array or an one-dimensional array.

The following is an array multidimensional array of three rows and three columns:

Example #

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

The output of the above code execution is as follows:

Three-row, three-column array multidimensional array of different index keys:

Example #

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

The output of the above code execution is as follows:

As you can see, in the above example, the array sets the specified index value to avoid the occurrence of nil value, which helps to save memory space.