Functions - Basic Examples¶

Python Functions¶

Basic Function¶

def greet(name):
    """Simple greeting function"""
    return f"Hello, {name}!"

# Call the function
message = greet("Alice")
print(message)  # Output: Hello, Alice!

Function with Parameters¶

def calculate_area(length, width):
    """Calculate rectangle area"""
    area = length * width
    return area

# Call with arguments
rectangle_area = calculate_area(5, 3)
print(f"Area: {rectangle_area}")  # Output: Area: 15

Function with Default Parameters¶

def power(base, exponent=2):
    """Calculate power with default exponent"""
    return base ** exponent

# Calls with and without default
result1 = power(3)        # Uses default exponent=2
result2 = power(3, 3)     # Uses provided exponent=3
print(f"3^2 = {result1}")   # Output: 3^2 = 9
print(f"3^3 = {result2}")   # Output: 3^3 = 27

Function with Multiple Returns¶

def get_grade(score):
    """Return grade and pass/fail status"""
    if score >= 60:
        return "A" if score >= 90 else "B", "Pass"
    else:
        return "F", "Fail"

# Unpack multiple return values
grade, status = get_grade(85)
print(f"Grade: {grade}, Status: {status}")  # Output: Grade: B, Status: Pass

Function with Variable Arguments¶

def sum_all(*numbers):
    """Sum variable number of arguments"""
    total = 0
    for num in numbers:
        total += num
    return total

# Different number of arguments
result1 = sum_all(1, 2, 3)
result2 = sum_all(10, 20, 30, 40, 50)
print(f"Sum 1: {result1}")  # Output: Sum 1: 6
print(f"Sum 2: {result2}")  # Output: Sum 2: 150

Java Methods¶

Basic Method¶

public class Calculator {

    // Simple method
    public static String greet(String name) {
        return "Hello, " + name + "!";
    }

    public static void main(String[] args) {
        String message = greet("Alice");
        System.out.println(message);  // Output: Hello, Alice!
    }
}

Method with Parameters¶

public class Geometry {

    // Method with parameters
    public static double calculateArea(double length, double width) {
        double area = length * width;
        return area;
    }

    public static void main(String[] args) {
        double rectangleArea = calculateArea(5.0, 3.0);
        System.out.println("Area: " + rectangleArea);  // Output: Area: 15.0
    }
}

Method with Overloading¶

public class MathOperations {

    // Method overloading - same name, different parameters
    public static int add(int a, int b) {
        return a + b;
    }

    public static double add(double a, double b) {
        return a + b;
    }

    public static int add(int a, int b, int c) {
        return a + b + c;
    }

    public static void main(String[] args) {
        System.out.println("Int sum: " + add(5, 3));        // 8
        System.out.println("Double sum: " + add(5.5, 3.2));  // 8.7
        System.out.println("Triple sum: " + add(1, 2, 3));   // 6
    }
}

Method with Variable Arguments¶

public class VarArgsExample {

    // Variable arguments method
    public static int sumAll(int... numbers) {
        int total = 0;
        for (int num : numbers) {
            total += num;
        }
        return total;
    }

    public static void main(String[] args) {
        int result1 = sumAll(1, 2, 3);
        int result2 = sumAll(10, 20, 30, 40, 50);
        System.out.println("Sum 1: " + result1);  // Output: Sum 1: 6
        System.out.println("Sum 2: " + result2);  // Output: Sum 2: 150
    }
}

C++ Functions¶

Basic Function¶

#include <iostream>
using namespace std;

string greet(string name) {
    return "Hello, " + name + "!";
}

int main() {
    string message = greet("Alice");
    cout << message << endl;  // Output: Hello, Alice!
    return 0;
}

Function with Parameters¶

double calculateArea(double length, double width) {
    double area = length * width;
    return area;
}

int main() {
    double rectangleArea = calculateArea(5.0, 3.0);
    cout << "Area: " << rectangleArea << endl;  // Output: Area: 15
    return 0;
}

Function with Default Parameters¶

// Default parameters (C++ specific syntax)
double power(double base, int exponent = 2) {
    double result = 1.0;
    for (int i = 0; i < exponent; i++) {
        result *= base;
    }
    return result;
}

int main() {
    double result1 = power(3);      // Uses default exponent=2
    double result2 = power(3, 3);   // Uses provided exponent=3
    cout << "3^2 = " << result1 << endl;  // Output: 3^2 = 9
    cout << "3^3 = " << result2 << endl;  // Output: 3^3 = 27
    return 0;
}

🎯 Function Best Practices¶

Practice	Python	Java	C++
Naming	`snake_case`	`camelCase`	`camelCase`
Return Type	Inferred	Explicit declaration	Explicit declaration
Default Values	`param=value`	Method overloading	`param=value`
Multiple Returns	Tuple	Create class	Struct/Pair

📚 Learn Functional Theory →