How to create function

// Function without parameters and return value

func greet() {

    print("Hello, world!")

}

// Function with parameters and return value

func addNumbers(_ a: Int, _ b: Int) -> Int {

    let sum = a + b

    return sum

}

// Function with external parameter names

func greet(person name: String, greeting: String = "Hello") {

    print("\(greeting), \(name)!")

}

// Function with multiple return values using a tuple

func calculateStatistics(scores: [Int]) -> (min: Int, max: Int, sum: Int) {

    let minScore = scores.min() ?? 0

    let maxScore = scores.max() ?? 0

    let sum = scores.reduce(0, +)

    return (minScore, maxScore, sum)

}

// Example usage

greet()

let result = addNumbers(5, 3)

print("Sum: \(result)")

greet(person: "John", greeting: "Hi")

let stats = calculateStatistics(scores: [5, 3, 9, 2])

print("Min: \(stats.min), Max: \(stats.max), Sum: \(stats.sum)")

Here's a breakdown of the code:

Basic Function (greet):

• greet is a simple function without parameters and return value.
• It prints "Hello, world!" when called.

Function with Parameters and Return Value (addNumbers):

• addNumbers takes two parameters (a and b) and returns their sum as an Int.
• It uses the + operator to add the two numbers and then returns the result.

Function with External Parameter Names (greet):

• greet takes two parameters: name and greeting.
• greeting has a default value of "Hello".
• The function prints a greeting message with the provided name and greeting.

Function with Multiple Return Values (calculateStatistics):

• calculateStatistics takes an array of integers (scores) and returns a tuple with three values: minimum, maximum, and sum of the array elements.
• It uses optional chaining (??) to provide default values for min and max in case the array is empty.

Example Usage:

• The functions are then called with different arguments and their results are printed.
• 
  
• When creating a function, consider whether it needs parameters, whether it returns a value, and how you want to name its parameters and return values. Swift allows for flexible and expressive function declarations to suit various needs.