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Functions

A function is a reusable block of code that performs a specific task. Breaking code into functions improves readability, reusability, and modularity.

C++ Functions​

Syntax​

returnType functionName(dataType param1, dataType param2) {
    // function body
    return value;
}

Example​

int add(int i, int j, int k) {
    return i + j + k;
}

Anonymous Function (Lambda)​

auto add = [](int x, int y) {
    return x + y;
};

C# Functions​

Syntax​

accessModifier returnType FunctionName(dataType param1, dataType param2) {
    // function body
    return value;
}

Example​

public int Add(int i, int j, int k) {
    return i + j + k;
}

Anonymous Function (Lambda)​

Func<int, int, int> add = (x, y) => x + y;

Java Functions​

Syntax​

// Inside a class
returnType functionName(dataType param1, dataType param2) {
    // function body
    return value;
}

Example​

public int add(int i, int j, int k) {
    return i + j + k;
}

Anonymous Function (Lambda – Java 8+)​

interface Add {
    int operation(int a, int b);
}

Add add = (a, b) -> a + b;

Python Functions​

Definition​

A function in Python is created using the def keyword. Functions can be nested, support multiple argument types, and allow anonymous (lambda) expressions.

Syntax​

def function_name(parameters):
    # function body
    return value

Example​

def add_numbers(i, j, k):
    return i + j + k

Default Arguments – Syntax​

def func_name(param=defaultValue):
    # body

Example​

def greet(name="User"):
    print("Hello", name)

Keyword Arguments – Syntax​

def func_name(param1, param2):
    # body

Example​

def profile(name, age):
    print(name, age)

profile(age=30, name="Alice")

Positional Arguments – Syntax​

def func_name(param1, param2):
    # body

Example​

def person(name, age):
    print(name, age)

person("Alice", 30)

Arbitrary Arguments – Syntax​

def func_name(*args):   # Non-keyword
def func_name(**kwargs):  # Keyword

Example​

def many_args(*args):
    for arg in args:
        print(arg)

def many_kwargs(**kwargs):
    for k, v in kwargs.items():
        print(f"{k} = {v}")

Nested Functions – Syntax​

def outer():
    def inner():
        # body
    inner()

Example​

def outer():
    msg = "Nested"
    def inner():
        print(msg)
    inner()

Anonymous Function (Lambda) – Syntax​

lambda arguments: expression

Example​

add = lambda x, y: x + y
print(add(2, 3))  # Output: 5

JavaScript Functions​

Syntax​

function functionName(param1, param2) {
    // body
}

Example​

function add(i, j, k) {
    return i + j + k;
}

Anonymous Function (Arrow Function)​

const add = (x, y) => x + y;

TypeScript Functions​

Definition​

TypeScript functions are like JavaScript functions but with type annotations for parameters and return values.

Syntax​

function functionName(param1: type, param2: type): returnType {
    // body
}

Example​

function add(i: number, j: number, k: number): number {
    return i + j + k;
}

Anonymous Function (Typed Arrow Function)​

const add = (x: number, y: number): number => x + y;