Lua Cheat Sheet

This cheat sheet provides a quick reference for the most common syntax and features in the Lua programming language.

Syntax and Variables

Lua is dynamically typed. Variables are global by default; use local for lexical scoping.

-- This is a single-line comment
 
--[[ This is a
     multi-line comment --]]
 
-- Use 'local' to avoid creating global variables
local name = "Lua"      -- String
local version = 5.4     -- Number (float)
local is_fast = true    -- Boolean
local data = nil        -- Nil (Lua's null type)

Data Types and Structures

Primitives

local my_string = "Hello"
local my_number = 42
local my_boolean = false
local my_nil = nil

Tables

The table is the only data structure in Lua. It can represent arrays, dictionaries, and objects.

As an array (1-based indexing):

local my_list = {"apple", "banana", "cherry"}
print(my_list[1]) -- "apple"

As a dictionary (hash map):

local person = {
    name = "Alice",
    age = 30
}
print(person.name) -- "Alice"
print(person["age"]) -- 30

Operators

Arithmetic

5 + 2  -- 7
5 * 2  -- 10
5 / 2  -- 2.5
5 ^ 2  -- 25 (Exponentiation)
5 % 2  -- 1 (Modulo)
"Hello" .. " " .. "World" -- "Hello World" (Concatenation)

Comparison and Logical

-- Comparison: == ~= < > <= >=
-- Note: ~= means "not equal to"
 
-- Logical: and, or, not
(5 > 2) and (2 > 5) -- false

Control Flow

Conditional Statements

if version > 5.3 then
    print("Modern Lua")
elif version == 5.3 then
    print("Classic Lua")
else
    print("Older Lua")
end

Loops

For Loop:

-- Numeric for loop
for i = 1, 5 do
    print(i)
end
 
-- Generic for loop (for tables)
for key, value in pairs(person) do
    print(key, value)
end

While Loop:

local count = 0
while count < 5 do
    print(count)
    count = count + 1
end

Functions

Functions are first-class citizens and are defined with the function keyword.

local function greet(name)
    return "Hello, " .. name .. "!"
end
 
print(greet("World"))

Metatables

Metatables allow you to modify the behavior of tables.

local my_table = {}
local metatable = {
    -- This metamethod is called for missing keys
    __index = function(tbl, key)
        return "Default Value"
    end
}
setmetatable(my_table, metatable)
 
print(my_table.some_key) -- "Default Value"