Language lab · Beginner → Scripting

🌙 Lua

Concept → trace → write code → run tests → explain why → improve → mini-project. Start in the browser if you like; set up your own computer when you are ready.

💻 Runs on your computerOfficial download & docs ↗

📖 Topics with real code (13)

Every verified output below was produced by running the code with Lua 5.4.9 Copyright (C) 1994-2026 Lua.org, PUC-Rio on 6 Nov 2026. Open a topic to edit the code and run it right here in your browser.

🌱 Beginner (5)

Variables and types

Lua has nil, boolean, number (integer and float), string, table and function. local keeps a variable inside its block. type() shows the type; tonumber and tostring convert.

local age = 15
local height = 1.62
local student = true
local name = "Asha"
print(name, age, height, student)
print(type(age), type(height), type(student), type(name), type(nil), math.type(age), math.type(height))
print(tonumber("88") + 2, 7 // 2, 7 / 2, tostring(90) .. "!")

✅ Verified output

Asha	15	1.62	true
number	number	boolean	string	nil	integer	float
90	3	3.5	90!

Operators and boolean logic

.. joins strings, // is floor division, ~= means "not equal". and/or return one of their operands, which gives a handy default idiom.

local a, b = 17, 5
print(a + b, a - b, a * b, a / b, a // b, a % b, a ^ 2)
print(a == b, a ~= b, not true)
local nickname = nil
print(nickname or "no nickname", false and "x" or "default")

✅ Verified output

22	12	85	3.4	3	2	289.0
false	true	false
no nickname	default

Conditionals

if … then … elseif … else … end. Only nil and false are false: 0 and "" are true in Lua.

local marks = 78
local grade
if marks >= 90 then grade = "A+"
elseif marks >= 75 then grade = "A"
elseif marks >= 35 then grade = "Pass"
else grade = "Fail" end
print("Grade: " .. grade)
if 0 then print("0 is true in Lua") end

✅ Verified output

Grade: A
0 is true in Lua

Loops

Numeric for (start, stop, step), generic for with ipairs/pairs, while and repeat…until. goto continue is a common way to skip a turn.

for i = 1, 5 do
  if i == 3 then goto continue end
  print("for " .. i)
  ::continue::
end
local n = 10
while n > 0 do
  if n < 4 then break end
  print("while " .. n)
  n = n - 3
end
local k = 0
repeat k = k + 1 until k >= 3
print("repeat ran " .. k .. " times")

✅ Verified output

for 1
for 2
for 4
for 5
while 10
while 7
while 4
repeat ran 3 times

Functions

Functions are values. They can take a variable number of arguments (...) and return several results.

local function area(length, width)
  width = width or 1
  return length * width
end
local function stats(...)
  local t, sum = { ... }, 0
  for _, v in ipairs(t) do sum = sum + v end
  return math.min(...), math.max(...), sum / #t
end
print(area(5, 3), area(7))
print(stats(4, 9, 2, 7))

✅ Verified output

15	7
2	9	5.5

🌿 Intermediate (5)

Tables as arrays

Tables are Lua's only data structure. As arrays they are 1-based; # gives the length; table.insert, table.sort and table.concat help.

local marks = { 72, 95, 64, 88 }
table.insert(marks, 91)
table.sort(marks)
print(table.concat(marks, ", "), "first " .. marks[1], "last " .. marks[#marks])
local squares = {}
for x = 1, 5 do if x % 2 == 1 then squares[#squares + 1] = x * x end end
print(table.concat(squares, " "))

✅ Verified output

64, 72, 88, 91, 95	first 64	last 95
1 9 25

Tables as dictionaries

Tables also map keys to values. pairs walks all keys (in no fixed order, so sort keys to print).

local stock = { pen = 40, book = 12 }
stock.eraser = 25
stock.pen = stock.pen - 5
local keys = {}
for k in pairs(stock) do keys[#keys + 1] = k end
table.sort(keys)
for _, k in ipairs(keys) do print(k, stock[k]) end
local freq = {}
for w in ("the cat and the hat and the bat"):gmatch("%a+") do freq[w] = (freq[w] or 0) + 1 end
print("the=" .. freq.the, "and=" .. freq["and"])

✅ Verified output

book	12
eraser	25
pen	35
the=3	and=2

Strings and patterns

string functions can be called with : on any string. Lua patterns (%d digits, %a letters) power find, match and gsub.

local t = ("  GayaGnan learning  "):match("^%s*(.-)%s*$")
print(t:upper(), t:gsub("learning", "labs"), #t)
print(string.format("Total: %.2f for %d items", 49.5 * 3, 3))
print(("level"):reverse() == "level")
for num in ("a1b22c333"):gmatch("%d+") do io.write(num, " ") end
print()

✅ Verified output

GAYAGNAN LEARNING	GayaGnan labs	17
Total: 148.50 for 3 items
true
1 22 333

Objects with metatables

Lua has no classes, but metatables and __index give objects and inheritance. The : syntax passes self.

local Account = {}
Account.__index = Account
function Account.new(owner, balance) return setmetatable({ owner = owner, balance = balance or 0 }, Account) end
function Account:deposit(amount)
  assert(amount > 0, "amount must be positive")
  self.balance = self.balance + amount
  return self
end
local acc = Account.new("Asha", 500):deposit(250)
print(acc.owner, acc.balance)
local Savings = setmetatable({}, { __index = Account })
Savings.__index = Savings
function Savings:addInterest() return self:deposit(self.balance * 0.05) end
local s = setmetatable(Account.new("Ravi", 1000), Savings)
print(s:addInterest().balance)

✅ Verified output

Asha	750
1050.0

Errors with pcall

error() raises an error; pcall runs a function in protected mode and returns false plus the message instead of crashing.

local function withdraw(balance, amount)
  if amount > balance then error("need " .. (amount - balance) .. " more", 0) end
  return balance - amount
end
print(pcall(withdraw, 100, 30))
print(pcall(withdraw, 100, 150))
local ok, err = pcall(function() return nil + 1 end)
print(ok, (err:gsub("^.-:%d+: ", "")))

✅ Verified output

true	70
false	need 50 more
false	attempt to perform arithmetic on a nil value

🌳 Advanced (3)

Closures

An inner function keeps access to the outer function's local variables. Each counter below has its own count.

local function makeCounter(step)
  local count = 0
  return function() count = count + (step or 1); return count end
end
local byOne, byTen = makeCounter(), makeCounter(10)
byOne(); byOne()
print(byOne(), byTen(), byTen())
local function compose(f, g) return function(x) return f(g(x)) end end
print(compose(function(x) return x + 1 end, function(x) return x * 2 end)(5))

✅ Verified output

3	10	20
11

Recursion and memoization

A cache table makes recursive Fibonacci fast. Lua 5.4 integers are 64-bit.

local memo = {}
local function fib(n)
  if n < 2 then return n end
  if not memo[n] then memo[n] = fib(n - 1) + fib(n - 2) end
  return memo[n]
end
local out = {}
for i = 0, 9 do out[#out + 1] = fib(i) end
print(table.concat(out, " "), fib(80))

✅ Verified output

0 1 1 2 3 5 8 13 21 34	23416728348467685

Coroutines

Coroutines pause with yield and resume later: cooperative multitasking used by game engines and network servers.

local producer = coroutine.wrap(function()
  for i = 1, 3 do coroutine.yield("item " .. i) end
  return "done"
end)
print(producer()); print(producer()); print(producer()); print(producer())
local co = coroutine.create(function(a, b) local c = coroutine.yield(a + b); return c * 2 end)
print(coroutine.resume(co, 2, 3))
print(coroutine.resume(co, 10))
print(coroutine.status(co))

✅ Verified output

item 1
item 2
item 3
done
true	5
true	20
dead

🛠️ Set up and verify

Install

winget install DEVCOM.Lua

brew install lua

sudo apt install lua5.4

Editor: Visual Studio Code with Lua (sumneko).
Create hello.lua
```
print('Hello, GayaGnan!')
```
Run it and check the version
```
hello.lua
lua -v
```
Health check: paste what your terminal printed.

Install one language at a time. These commands only install or print versions; nothing here deletes files. Versions change: check the official page and note the version you installed.

🧭 The 14-lab path

00 · Setup and verify — install the runtime and editor, run hello world, print the version, fix PATH
01 · Syntax and trace — follow each line and the value of every variable
02 · Logic — conditionals and decision trees
03 · Loops — trace tables and loop challenges
04 · Functions — break problems down and test each piece
05 · Data structures — lists, maps, stacks, queues and trees you can see
06 · Debugging — bug cases with a hint ladder
07 · Algorithms — search, sort and Big-O comparison
08 · Files and data — read and write fixture files
09 · API or database — talk to a mock API or a sandbox database
10 · Testing — write tests and read failing assertions
11 · Security — secure coding and dependency hygiene for this language
12 · Project — one portfolio mini-project
13 · Assessment — quiz, coding test, rubric and an explain-your-answer prompt

📚 Modules

types
operators
conditionals
loops
functions
tables as arrays
tables as dictionaries
strings and patterns
metatables
pcall
closures
memoization
coroutines

🏗️ Mini-projects

Text adventure game
Config-file parser
Game-engine scripting (concepts)

Projects use synthetic data only.