Skip to content

LUA

Lua is a small, fast, embeddable scripting language designed to be:

  • Lightweight: very small footprint
  • Embeddable: easy to integrated into C/C++ apps
  • Flexible: minimal syntax

Install

ubuntu 24.04
1
sudo apt install lua5.4

VSCode

marketplace

Core

Tables are EVERYTHING

Lua doesn't have:

  • arrays
  • struct
  • classes

instead os has tables which as as:

  • array
  • dictionaries
  • objects
  • module

Table are dictionary

1
2
3
4
5
6
7
8
person = {
    name = "Amir",
    age = 30,
    city = "Taipei"
}

print(person.name)       -- dot syntax (for string keys)
print(person["age"])     -- bracket syntax
Nested
1
2
3
4
5
6
7
8
9
user = {
    name = "Amir",
    address = {
        city = "Taipei",
        zip = 100
    }
}

print(user.address.city)
Iterate
1
2
3
for key, value in pairs(person) do
    print(key, value)
end

Missing key return nil

Table as array

1
2
arr = {10, 20, 30}
print(arr[1])  -- Lua starts at 1!

Lua starts at 1

Function first class

Function are values:

  • store in variables
  • pass as argument
  • return from functions
1
2
3
4
5
function add(a, b)
    return a + b
end

print(add(2, 3))

1
2
f = add
print(f(5, 6))

Data types

  • nil (null)
  • number
  • string
  • boolean
  • table
  • function

Variables

In Lua, variables are:

  • Global by default ❗
  • Local only if you explicitly say local
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
function foo()
    local x = 10
end

function bar()
    print(x)
end

foo()
bar()   -- nil

Local variable scope

  • block scope
  • function scope
  • file/module scope

Strings

Multiline strings

1
2
3
4
5
s = [[
line 1
line 2
line 3
]]

Concatenation

Lua uses .. 

1
2
3
4
name = "Amir"
msg = "Hello " .. name

print(msg)

string methods

Function Description Example Result
string.len(s) Get length of string string.len("abc") 3
#s Length operator (shortcut) #"abc" 3
string.sub(s, i, j) Substring from index i to j string.sub("hello",1,4) "hell"
string.upper(s) Convert to uppercase string.upper("abc") "ABC"
string.lower(s) Convert to lowercase string.lower("ABC") "abc"
string.reverse(s) Reverse string string.reverse("abc") "cba"
string.find(s, pattern) Find pattern (returns indices) string.find("hello","lo") 4,5
string.match(s, pattern) Extract first match string.match("a1b2","%d+") "1"
string.gmatch(s, pattern) Iterate over matches loop over "a1b2" "a1","b2"
string.gsub(s, pattern, repl) Replace occurrences string.gsub("hi all","all","Lua") "hi Lua"
string.format(fmt, ...) Format string (like printf) string.format("%d",10) "10"
string.byte(s, i) Get ASCII/byte value string.byte("A") 65
string.char(...) Convert numbers to chars string.char(65) "A"
string.rep(s, n) Repeat string n times string.rep("ab",3) "ababab"

module

metatable

oop