YouTipLua Arrays
An array is a collection of elements of the same data type arranged in a certain order. It can be a one-dimensional array or a multi-dimensional array.
In Lua, an array is not a specific data type, but a data structure used to store a set of values.
In fact, Lua does not have a dedicated array type. Instead, it uses a data structure called a **"table"** to implement array functionality.
The index keys of a Lua array can be represented by integers, and the size of the array is not fixed.
In Lua, index values start from 1, but you can also specify a start from 0.
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## One-Dimensional Arrays
A one-dimensional array is the simplest type of array, with a logical structure of a linear list.
Access array elements using indices:
## Example
-- Create an array
local myArray = {10, 20, 30, 40, 50}
-- Access array elements
print(myArray) -- Output: 10
print(myArray) -- Output: 30
The output of the above code is:
10 30
To calculate the length of an array (i.e., the number of elements in the array), you can use the # operator:
## Example
local myArray = {10, 20, 30, 40, 50}
-- Calculate array length
local length = #myArray
print(length) -- Output: 5
The output of the above code is:
5
A one-dimensional array can be traversed using a **for** loop, as shown in the following example:
## Example
-- Create an array
local myArray = {10, 20, 30, 40, 50}
-- Loop through the array
for i = 1, #myArray do
print(myArray)
end
The output of the above code is:
10 20 30 40 50
Lua indices default to starting from 1:
## Example
array = {"Lua", "Tutorial"}
for i = 0, 2 do
print(array)
end
The output of the above code is:
nil Lua Tutorial
As you can see, we can use integer indices to access array elements. If the specified index has no value, it returns **nil**.
In addition, we can also use negative numbers as array index values:
## Example
array = {}
for i = -2, 2 do
array = i * 2
end
for i = -2, 2 do
print(array)
end
The output of the above code is:
-4 -2 0 2 4
We can also modify elements in an array:
## Example
-- Create an array
local myArray = {10, 20, 30, 40, 50}
-- Modify an array element
myArray = 25
-- Loop through the array
for i = 1, #myArray do
print(myArray)
end
The output of the above code is:
10 25 30 40 50
We can also add elements to an array:
## Example
-- Create an array
local myArray = {10, 20, 30, 40, 50}
-- Add a new element to the end of the array
myArray[#myArray + 1] = 60
-- Loop through the array
for i = 1, #myArray do
print(myArray)
end
The output of the above code is:
10 20 30 40 50 60
We can also remove elements from an array:
## Example
-- Create an array
local myArray = {10, 20, 30, 40, 50}
-- Remove the third element
table.remove(myArray, 3)
-- Loop through the array
for i = 1, #myArray do
print(myArray)
end
The output of the above code is:
10 20 40 50
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## Multi-Dimensional Arrays
A multi-dimensional array is an array that contains arrays, or a one-dimensional array whose index key corresponds to another array.
The following is a three-by-three matrix multi-dimensional array:
## Example
-- Initialize the array
array = {}
for i = 1, 3 do
array = {}
for j = 1, 3 do
array = i * j
end
end
-- Access the array
for i = 1, 3 do
for j = 1, 3 do
print(array)
end
end
The output of the above code is:
1 2 3
2 4 6
3 6 9
A three-by-three matrix multi-dimensional array with different index keys:
## Example
-- 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 of the above code is:
1 2 3
2 4 6
3 6 9
As you can see, in the examples above, the array has specified index values. This helps avoid nil values and is beneficial for saving memory space.