Hàm (Function) trong Swift

func sayHello() {
    print("Hello, Swift!")
}
 
sayHello()  // Gọi hàm

func greet(name: String) {
    print("Hello, \(name)!")
}
 
greet(name: "Alice")

func sum(a: Int, b: Int) -> Int {
    return a + b
}
 
let result = sum(a: 10, b: 20)
print(result)  // 30

func greet(person name: String) {
    print("Hello, \(name)!")
}
 
greet(person: "Alice")  // 'person' là external label

func sum(_ a: Int, _ b: Int) -> Int {
    return a + b
}
 
sum(10, 20)  // Không cần label

func greet(name: String = "Guest", greeting: String = "Hello") {
    print("\(greeting), \(name)!")
}
 
greet()                          // Hello, Guest!
greet(name: "Alice")            // Hello, Alice!
greet(name: "Bob", greeting: "Hi")  // Hi, Bob!

func sum(_ numbers: Int...) -> Int {
    var total = 0
    for number in numbers {
        total += number
    }
    return total
}
 
print(sum(1, 2, 3))        // 6
print(sum(1, 2, 3, 4, 5))  // 15

func increment(_ value: inout Int) {
    value += 1
}
 
var count = 5
increment(&count)
print(count)  // 6

func minMax(array: [Int]) -> (min: Int, max: Int) {
    return (array.min()!, array.max()!)
}
 
let result = minMax(array: [1, 5, 3, 9, 2])
print("Min: \(result.min), Max: \(result.max)")

func findIndex(of value: Int, in array: [Int]) -> Int? {
    for (index, item) in array.enumerated() {
        if item == value {
            return index
        }
    }
    return nil
}
 
if let index = findIndex(of: 5, in: [1, 3, 5, 7]) {
    print("Found at index: \(index)")
}

func add(a: Int, b: Int) -> Int {
    return a + b
}
 
var mathFunction: (Int, Int) -> Int = add
print(mathFunction(5, 3))  // 8

func calculate() -> Int {
    func add(a: Int, b: Int) -> Int {
        return a + b
    }
 
    return add(a: 5, b: 3)
}
 
print(calculate())  // 8