Lua/tutorial

This page is aimed to describe the main aspects of the Lua programming language.

Essential elements

Functions

A function is basically a chunk of code which does something and can be told to do this thing from somewhere else. It can also pass data about what it did back to the place which told it to run (the place which "called" it).

print("Hello world!")

Defining: You are also able to write and call your own functions

function MyFunction()
	print("Hello world!")
	return 0
end

myFunction()

Parameters: With the parameters you can pass useful data that you'll use in this the next process

function debugMessage(text)
	print("Lua Message: "..text)
end

debugMessage("This is a test")

Return: return functionality in functions, are used to return back some data produced by calling this function. Please, take a look at variables [1]

myVar = 10

function Doubler(x)
	return x+x
end

myDoubler = Doubler(myVar)

So the function Doubler will return a variable multiplied by 2

Variables

The variables can be defined normally either globally or locally. Lua doesn't allow static variables.

There are a few types of variable (string, number, boolean, table, userdata)

myVariable = "This is a test string"

myVariable = 12345

myVariable = true

myVariable = {"foo","bar",100}

Format in strings

You can also add format to the string to print different things, for example

Hour = 15
Minutes = 37
TextFormat = "It's %s Hours with %s Minutes"

print(string.format(TextFormat,Hour,Minutes))

Will produce: It's 15 Hours with 37 Minutes

Local Variables

Usually, local variables are used in functions

var = 4
function printDoubler(x)
	local y = x+x -- Our variable (y) will be local. (Means that it can only be used inside this chunk)
	print(y)
end

-- The variable (y) is null outside the function, (can't be used outside the function)
printDoubler(var)

Conditional

Conditionals are another important part at scripting, they use the next structure

if (condition) then
	-- Our script
end

For example, we can check the result of substracting 2 values

value1 = 70
value2 = 20
if (value1 - value2 == 50) then
	print("Our result is 50")
end

Other methods for conditionals are:

x > y (when X is higher than Y) (Numbers)
x < y (when X is lower than Y) (Numbers)
x == y (when X is the same of Y) (Numbers and strings)
x ~= y (when X is different than Y) (Numbers and strings)
x >= y (when X is the same or higher than Y) (Numbers)
x <= y (when X is the same or lower than Y) (Numbers)

or: the "or" keyword can be used also when another condition happens in the same conditional, so the condition must work.

value1 = 60
value2 = 20
value3 = 30
if (value1 - value2 == 70 or value1 + value3 == 80 or value3 + value2 == value1 + 10) then
	print("Some of our condition worked")
end

and: the "and" keyword can be used to force to check when 2 conditions or more, worked in a conditional

value1 = 60
value2 = 20
value3 = 30
if (value2 + value3 == 50 and value1 - value3 == 25) or (value1 + value3 == 90 and value2 - value3 == -10) then
	print("Some of our conditionals worked")
end

Note: Parenthesis in conditionals are alternative

Table

A table is a variable that allows you to set multiple variables inside it (by sorting). In Lua, the tables don't need a specific size.

myArray = {}

You can store variables by using a specific id (slot) in it

myArray[slot] = "This is a test string inside of an array"

For example

myArray = {}
myArray[1] = "Hello"
myArray[2] = "World!"

That would be the same as if it was done like this:

myArray = {"Hello","World!"}

String Slots: String slots are also allowed to be used, but you may not use spaces in it.

WeaponDamage = {}
WeaponDamage["M4A1"] = 22

Or

WeaponDamage = {}
WeaponDamage.M4A1 = 22

Or

WeaponDamage = {
	M4A1 = 22
}

Why tables? Tables are better and more efficient than creating an amount of variables, is a way to "optimize" our code. So we can prevent cases like this:

player1 = 0
player2 = 0
player3 = 0

function setPlayer(id,value)
	if id == 1 then
		player1 = value
	end
	if id == 2 then
		player2 = value
	end
	if id == 3 then
		player3 = value
	end
end

You can optimize this code by doing this:

playerValue = {}

function setPlayer(id,value)
	playerValue[id] = value
end

Loops

while: the loop "while" uses a format like of conditional, but this one repeats while the condition works

a = 0
while (a < 10) do
	a = a + 1
end

for: the loop "for" is usually used to count, the format used is the initialization, finalization, step. If step is not specified, it's automatically switch to 1.

for i = 1, 32 do
	print(i)
end

In that case, we start from 1 and stop at 32 by step 1, means we called the function "print" 32 times

repeat-until: This loop is like the loop while, but it doesn't freeze the program and works only when the condition doesn't work

a = 0
repeat
	a = a + 1
until a >= 5

First script

So we seem to be ready, now we can start to create our first script, let's create a basic welcome message for Counter-Strike 2D
We have to check our first resource, a hook that calls a function when someone joins

addhook("join","player_join")

So we will call our function "player_join"

function player_join(id)
end

But it will do nothing if we don't put the welcome message

function player_join(id)
	msg2(id, string.format("Welcome to my server, %name !", player(id,"name")))
end

So, our full code would look like this

addhook("join","player_join")
function player_join(id)
	msg2(id, string.format("Welcome to my server, %name !", player(id,"name")))
end

With Lua we can also create a detector that tells when someone important joins, for example if DC joins to your server

-- Create the hook
addhook("join","player_join")

-- Create the function
function player_join(id)
	-- Check the USGN id of this player
	if player(id, "usgn") == 1 then

		-- The USGN id of this user is 1, means that is real DC
		-- Throw a message warning everyone that DC is in that server
		msg("WARNING: DC has joined to the server!!")

	-- stop our condition
	end

-- stop our function
end