Argument Labels

// ARGUMENT LABELS EXPLAINED
// Swift has TWO names for each parameter:
// 1. External name (used when calling)
// 2. Internal name (used inside function)

// DEFAULT: Same name for both
func greet(name: String) {
    print("Hello, \(name)!")  // 'name' used internally
}
greet(name: "Alice")  // 'name' used externally

// CUSTOM EXTERNAL LABEL
func greet(person name: String) {
    print("Hello, \(name)!")  // 'name' is internal
}
greet(person: "Bob")  // 'person' is external

// WHY USE DIFFERENT LABELS?
// Makes function calls read like English!

func send(message text: String, to recipient: String) {
    print("Sending '\(text)' to \(recipient)")
}
send(message: "Hello!", to: "Charlie")
// Reads: "send message 'Hello!' to Charlie"

// OMITTING EXTERNAL LABEL WITH _
func add(_ a: Int, _ b: Int) -> Int {
    return a + b
}
print(add(5, 3))  // No labels needed!

// Common pattern: first parameter without label
func contains(_ element: String, in array: [String]) -> Bool {
    return array.contains(element)
}
contains("apple", in: ["apple", "banana"])

// MULTIPLE LABELS EXAMPLE
func move(from source: String, to destination: String) {
    print("Moving from \(source) to \(destination)")
}
move(from: "Home", to: "School")

// MAKING API-LIKE FUNCTIONS
func setColor(red r: Int, green g: Int, blue b: Int) {
    print("RGB(\(r), \(g), \(b))")
}
setColor(red: 255, green: 128, blue: 0)

// PREPOSITION PATTERN
func insert(_ item: String, at index: Int) {
    print("Inserting \(item) at position \(index)")
}
insert("new item", at: 5)

// Best practices:
// 1. Omit label for first param if it's obvious
// 2. Use prepositions (to, from, at, in, with)
// 3. Make calls read like English sentences