lua.md

lua

basics

• dynamically typed
• high-level
• designed for embedded use in applications
  • complete language is small
• easy to read and understand
• blocks are NOT defined by indentation
• garbage collection
• functions are values (i.e. first-class citizens)
• doesn't have built-in class-based OOP, but supports object-oriented programming through prototype-based approach:
  • tables and metatables
  • can implement objects, inheritance, and polymorphism
• immutable strings
• parentheses in if statements are optional
• can also be used for functional programming

data types

• nil: represents null or no value
• boolean: true or false
• number
• string
• table: used for arrays, dictionaries and objects

x = 10            -- number
y = "Hello"       -- string
is_active = true  -- boolean
z = nil           -- nil

fruits = {"apple", "banana", "cherry"}
print(fruits[1])  -- Output: apple

person = {name = "John", age = 30}
local person = {
    name = "John",
    greet = function(self)
        print("Hello, my name is " .. self.name)
    end
}

print(person["name"])  -- Output: John

-- Method call
person:greet()  -- Output: Hello, my name is John

string manipulation

str1 = "Hello"
str2 = "World"
result = str1 .. " " .. str2  -- Concatenation with a space
print(result)  -- Output: Hello World

str = "Hello"
-- calculates string length
print(#str)  -- Output: 5

-- s: The string.
-- i: The starting index (1-based).
-- j: The ending index (optional). If not specified, it extracts up to the end.
string.sub(s, i, j)

-- removes leading and trailing whitespaces
str = str:gsub('^%s+', ''):gsub('%s+$', '')

• string.gsub(input_string, pattern, replacement)
  • input_string: the string to modify
  • pattern: the pattern to search for
  • replacement: the string to replace the pattern with

if else

x = 15
if x > 20 then
  print("x is greater than 20")
elseif x > 10 then
  print("x is greater than 10")
else
  print("x is 10 or less")
end

loops

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

for i = 1, 5 do
  print(i)
end

functions

function greet(name)
  return "Hello, " .. name
end

print(greet("Alice"))  -- Output: Hello, Alice

modules

used to organize code into reusable libraries

creating a module:

-- mymodule.lua
local M = {}
function M.sayHello()
  print("Hello from module!")
end
return M

using a module:

local mymodule = require("mymodule")
mymodule.sayHello()  -- Output: Hello from module!