Function Basics

// What is a Function?
// A reusable block of code that performs a specific task

// DEFINING A FUNCTION
func sayHello() {
    print("Hello, World!")
}

// CALLING A FUNCTION
sayHello()  // Output: Hello, World!
sayHello()  // Can call as many times as needed!

// FUNCTION WITH A PARAMETER
func greet(name: String) {
    print("Hello, \(name)!")
}

greet(name: "Alice")   // Hello, Alice!
greet(name: "Bob")     // Hello, Bob!

// FUNCTION WITH MULTIPLE PARAMETERS
func introduce(name: String, age: Int) {
    print("Hi, I'm \(name) and I'm \(age) years old.")
}

introduce(name: "Charlie", age: 12)

// FUNCTION WITH RETURN VALUE
func add(a: Int, b: Int) -> Int {
    return a + b
}

let sum = add(a: 5, b: 3)
print("Sum: \(sum)")  // Sum: 8

// Use the result directly
print(add(a: 10, b: 20))  // 30

// SINGLE EXPRESSION FUNCTIONS
// If the function has only one line, you can omit 'return'
func multiply(a: Int, b: Int) -> Int {
    a * b  // Implicit return
}

print(multiply(a: 4, b: 5))  // 20

// WHY USE FUNCTIONS?
// 1. Avoid repeating code (DRY - Don't Repeat Yourself)
// 2. Make code easier to read and understand
// 3. Easy to test and fix bugs
// 4. Can reuse in different parts of your program