Lua Cheatsheet

Hello World

print("Hello, World!")

Comments

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Data type

Lua has the following basic data types:

nil       -- Represents the absence of a value
boolean   -- true or false
number    -- Real (double-precision) numbers
string    -- Immutable sequences of characters
table     -- Associative arrays (key-value pairs)
function  -- Blocks of reusable code
userdata  -- Used to represent C data
thread    -- For managing coroutines

Constant

Lua does not have explicit constant declarations, but it can be emulated using conventions:

local PI = 3.14159 -- Naming convention for constants is UPPER_CASE

Operators

Operator	Example	Same as
+	x = 5 + 3	Addition x = 8
-	x = 5 - 3	Subtraction x = 2
*	x = 5 * 3	Multiplication x = 15
/	x = 6 / 3	Division x = 2
%	x = 5 % 3	Modulus x = 2
^	x = 2 ^ 3	Exponentiation x = 8
==	x == 5	Compare if x equals 5
~=	x ~= 5	Compare if x does not equal 5
<	x < 5	Compare if x is less than 5
>	x > 5	Compare if x is greater than 5
<=	x <= 5	Compare if x is less than or equal to 5
>=	x >= 5	Compare if x is greater than or equal to 5
and	x > 1 and x < 5	Logical AND between conditions
or	x < 1 or x > 5	Logical OR between conditions
not	not x == 5	Logical NOT of condition
..	"Lua " .. "is awesome"	Concatenates strings into "Lua is awesome"
#	#t	Returns the length of a string or table t

If else

local x = 10
 
if x > 5 then
    print("x is greater than 5")
elseif x == 5 then
    print("x is equal to 5")
else
    print("x is less than 5")
end

Switch

Lua has not built-in switch statement. Instead we can use if-elseif.

local choice = 2
 
if choice == 1 then
    print("Option 1 selected")
elseif choice == 2 then
    print("Option 2 selected")
elseif choice == 3 then
    print("Option 3 selected")
else
    print("Invalid option")
end

Loops

While loop

local count = 0 
while count < 5 do 
	print("Count is:", count) 
	count = count + 1 
end

For loop

for i = 1, 5 do
	print("i is:", i)
end

Repeat Until loop

local value = 0 
repeat 
	print("Value is:", value) 
	value = value + 1 
until value > 5

Iterating over a table

local fruits = {"Apple", "Banana", "Cherry"} 
for index, fruit in ipairs(fruits) do 
	print(index, fruit) 
end

Variables and Scope

Variables inLua are dynamically typed

local x = 10 -- Local variable
y = 20       -- Global variable (avoid unless necessary)

Lua uses block scoping

do
	local z = 30 -- Scope limited to this block
	print(z)     -- Outputs: 30
end
print(z)         -- Error: z is not defined

Tables

Tables are the primary data structure inLua.

-- Tables are the primary data structure in Lua.
local t = {}            -- Create an empty table
t["key"] = "value"      -- Key-value pair
t[1] = "First Element"  -- Numeric index (arrays)
t.name = "Lua Table"    -- Shortcut for string keys
 
-- Iterating over a table
for k, v in pairs(t) do
    print(k, v)
end
 
-- Multi-dimensional tables
local matrix = {
    {1, 2, 3},
    {4, 5, 6},
    {7, 8, 9}
}
print(matrix[1][2])  -- Outputs: 2

Functions

-- Defining a function
function greet(name)
    return "Hello, " .. name
end
 
-- Calling a function
print(greet("World"))  -- Outputs: Hello, World
 
-- Anonymous functions
local add = function(a, b)
    return a + b
end
print(add(3, 5))  -- Outputs: 8
 
-- Varargs (Variable number of arguments)
function sum(...)
    local s = 0
    for _, v in ipairs({...}) do
        s = s + v
    end
    return s
end
print(sum(1, 2, 3, 4))  -- Outputs: 10

Coroutines

Coroutines allow cooperative multitasking inLua.

co = coroutine.create(function()
    for i = 1, 3 do
        print("Coroutine iteration:", i)
        coroutine.yield()
    end
end)
 
coroutine.resume(co)  -- Outputs: Coroutine iteration: 1
coroutine.resume(co)  -- Outputs: Coroutine iteration: 2
coroutine.resume(co)  -- Outputs: Coroutine iteration: 3

Error Handling

Using pcall (protected call) for error handling.

local status, err = pcall(function()
    error("An error occurred!")
end)
if not status then
    print("Error:", err)
end