Lua / C# Comparison¶

Time:

This article is a general overview of the Lua programming language and how its syntax compares to C#.

General Differences¶

Comments¶

Lua¶

-- Single line comment

--[[
	Block comment
--]]

C#¶

// Single line comment

/*
	Block comment
*/

Strings¶

Lua¶

-- Multi-line string
[[This is a string that,
when printed, will appear
on multiple lines]]



-- Concatenation
s1 = "This is a string "
s2 = "made with two parts."
endString = s1 .. s2

C#¶

// Multi-line string
"This is a string that,\nwhen printed, will appear\n on multiple lines."



// Concatenation
string s1 = "This is a string ";
string s2 = "made with two parts.";
string endString = s1 + s2;

Conditional Operators¶

Lua C#

Equal To == ==

Greater Than > >

Less Than < <

Greater Than or Equal To >= >=

Less Than or Equal To <= <=

Not Equal To ~= !=

And and &&

Or or ||

Arithmetic Operators¶

Lua C#

Addition + +

Subtraction - -

Multiplication * *

Division / /

Modulus % %

Exponentiation ^ **

Reserved Keywords¶

Below are Lua’s reserved keywords mapped to their C# equivalent. Not all C# keywords are shown.

Lua C#

and

break break

do do

if if

else else

elseif else if

then

end

true true

false false

for for / foreach

function

in in

local

nil null

not

or

repeat

return return

until

while while

Line Endings¶

Semicolons are not required in Lua, but they will work if used in your code.

Scoping¶

In Lua, variables and logic can be written in a tighter scope than their function or class by nesting the logic within do and end keywords, similar to nesting it within curly brackets {} in C#. For more details on scope in Lua, please see the /articles/Scope|Scope article.

Lua¶

local example = "Example text"

do
	example = example .. " changed!"
	print(example)  -- Outputs 'Example text changed!'
end

print(example)  -- Outputs 'Example text'

C#¶

string example = "Example text";

{
	example += " changed!";
	Console.WriteLine(example);  // Outputs 'Example text changed!'
}

Console.WriteLine(example);  // Outputs 'Example text'

Variables¶

In Lua, variables do not specify their type when being declared/defined. Also, Lua variables do not have access modifiers, although you may prefix “private” variables with an underscore for readability.

Lua¶

local variableName = "value"

-- "Public" declaration
local variableName

-- "Private" declaration
local _variableName

C#¶

string variableName = "value";

// Public declaration
public string variableName

// Private declaration
string variableName;

Loops¶

For Loops¶

Lua¶

-- Forward loop
for i = 1, 10 do
	doSomething()
end



-- Reverse loop
for i = 10, 1, -1 do
	doSomething()
end

C#¶

// Forward loop
for (int i = 1; i <= 10; i++) {
	doSomething();
}



// Reverse loop
for (int i = 10; i >= 1; i--) {
	doSomething();
}

While Loops¶

Lua¶

while boolExpression do
	doSomething()
end



repeat
	doSomething()
until not boolExpression

C#¶

while (boolExpression) {
	doSomething();
}



do {
	doSomething();
} while (boolExpression)

For Each Loops¶

Lua¶

local abcList = {"a", "b", "c"}

for i, v in ipairs(abcList) do
	print(v)
end



local abcDictionary = { a=1, b=2, c=3 }

for k, v in pairs(abcDictionary) do
	print(k, v)
end

C#¶

List abcList = new List{"a", "b", "c"};

foreach (string v in abcList) {
	Console.WriteLine(v);
}



Dictionary abcDictionary = new Dictionary
{ {"a", 1}, {"b", 2}, {"c", 3} };

foreach (KeyValuePair entry in abcDictionary) {
	Console.WriteLine(entry.Key + " " + entry.Value);
}

Conditional Statements¶

Lua¶

-- One condition
if boolExpression then
	doSomething()
end

-- Multiple conditions
if not boolExpression then
	doSomething()
elseif otherBoolExpression then
	doSomething()
else
	doSomething()
end

C#¶

// One condition
if (boolExpression) {
	doSomething();
}

// Multiple conditions
if (!boolExpression) {
	doSomething();
}
else if (otherBoolExpression) {
	doSomething();
}
else {
	doSomething();
}

Ternary Operations¶

Lua does not offer a direct equivalent to the C ternary operator a?b:c. However, the Lua idiom (a and b) or c offers a close approximation, provided b is not false.

Lua¶

local max = (x>y and x) or y

C#¶

int max = (x>y) ? x: y;

Functions¶

Be sure to read our article on articles/Understanding Functions in Roblox|Functions to get a deeper understanding of Lua functions.

Generic Functions¶

Lua¶

-- Generic function
local function increment(number)
	return number + 1
end

C#¶

// Generic function
int increment(int number) {
	return number + 1;
}

Variable Argument Number¶

Lua¶

-- Variable argument number
local function variableArguments(...)
	print(...)
end

C#¶

// Variable argument number
void variableArguments(params string[] inventoryItems) {
	for (item in inventoryItems) {
		Console.WriteLine(item);
	}
}

Named Arguments¶

Lua¶

-- Named arguments
local function namedArguments(args)
	return args.name .. "'s birthday: " .. args.dob
end

namedArguments{name="Bob", dob="4/1/2000"}

C#¶

// Named arguments
string namedArguments(string name, string dob) {
	return name + "'s birthday: " + dob;
}

namedArguments(name: "Bob", dob: "4/1/2000");

Try/Catch Structures¶

Lua¶

local function fireWeapon()
	if not weaponEquipped then
		error("No weapon equipped!")
	end
	-- Proceed...
end

local success, errorMessage = pcall(fireWeapon)
if not success then
	print(errorMessage)
end

C#¶

void fireWeapon() {
	if (!weaponEquipped) {
		// Use a user-defined exception
		throw new InvalidWeaponException("No weapon equipped!");
	}
	// Proceed...
}

try {
	fireWeapon();
} catch (InvalidWeaponException ex) {
	// An error was raised
}

Tables¶

Be sure to read the articles/Table|Tables article to get a deeper understanding on how you can use tables in Lua.

Dictionary Tables¶

Tables in Lua can be used just like Dictionaries in C#.

Lua¶

local dictionary = {
	val1 = "this",
	val2 = "is"
}

print(dictionary.val1)  -- Outputs 'this'
print(dictionary[val1])  -- Outputs 'this'

dictionary.val1 = nil  -- Removes 'val1' from table
table.remove(dictionary, 1)  -- Also removes 'val1' from table

dictionary["val3"] = "a dictionary"  -- Overwrites 'val3' or sets new key-value pair

C#¶

Dictionary dictionary = new Dictionary()
{
	{ "val1", "this" },
	{ "val2", "is" }
};

Console.WriteLine(dictionary["val1"]);  // Outputs 'this'

dictionary.Remove("val1");  // Removes 'val1' from dictionary

dictionary["val3"] = "a dictionary";  // Overwrites 'val3' or sets new key-value pair
dictionary.Add("val3", "a dictionary");  // Creates a new key-value pair

Numerically-Indexed Tables¶

Tables in Lua can also be used like a List in C#. The key difference is that indices start at 1 with Lua and 0 with C#.

Lua¶

local NPCAttributes = {"strong", "intelligent"}

print(NPCAttributes[1])  -- Outputs 'strong'

print(#NPCAttributes)  -- Outputs the size of the list

-- Append to the list
table.insert(NPCAttributes, "humble")
-- Another way...
NPCAttributes[#NPCAttributes+1] = "humble"

-- Insert at the beginning of the list
table.insert(NPCAttributes, 1, "brave")

-- Remove item at a given index
table.remove(NPCAttributes, 3)

C#¶

List NPCAttributes = new List{"strong", "intelligent"};

Console.WriteLine(NPCAttributes[0]);  // Outputs 'strong'

Console.WriteLine(NPCAttributes.Count);  // Outputs the size of the list

// Append to the list
NPCAttributes.Add("humble");
// Another way...
NPCAttributes.Insert(NPCAttributes.Count, "humble");

// Insert at the beginning of the list
NPCAttributes.Insert(0, "brave");

// Remove item at a given index
NPCAttributes.Remove(2);

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