[Swift 공식 문서] 6. Functions

func greet(person: String) -> String { let greeting = "Hello, " + person + "!" return greeting }

print(greet(person: "Anna")) // Prints "Hello, Anna!" print(greet(person: "Brian")) // Prints "Hello, Brian!"

func greet(person: String, alreadyGreeted: Bool) -> String { if alreadyGreeted { return greetAgain(person: person) } else { return greet(person: person) } } print(greet(person: "Tim", alreadyGreeted: true)) // Prints "Hello again, Tim!"

func greet(person: String) { print("Hello, \(person)!") } greet(person: "Dave") // Prints "Hello, Dave!"

func printAndCount(string: String) -> Int { print(string) return string.count } func printWithoutCounting(string: String) { let _ = printAndCount(string: string) } printAndCount(string: "hello, world") // prints "hello, world" and returns a value of 12 printWithoutCounting(string: "hello, world") // prints "hello, world" but doesn't return a value

func minMax(array: [Int]) -> (min: Int, max: Int) { var currentMin = array[0] var currentMax = array[0] for value in array[1..<array.count] { if value < currentMin { currentMin = value } else if value > currentMax { currentMax = value } } return (currentMin, currentMax) }

let bounds = minMax(array: [8, -6, 2, 109, 3, 71]) print("min is \(bounds.min) and max is \(bounds.max)") // Prints "min is -6 and max is 109"

func minMax(array: [Int]) -> (min: Int, max: Int)? { if array.isEmpty { return nil } var currentMin = array[0] var currentMax = array[0] for value in array[1..<array.count] { if value < currentMin { currentMin = value } else if value > currentMax { currentMax = value } } return (currentMin, currentMax) }

if let bounds = minMax(array: [8, -6, 2, 109, 3, 71]) { print("min is \(bounds.min) and max is \(bounds.max)") } // Prints "min is -6 and max is 109"

func greeting(for person: String) -> String { "Hello, " + person + "!" } print(greeting(for: "Dave")) // Prints "Hello, Dave!" func anotherGreeting(for person: String) -> String { return "Hello, " + person + "!" } print(anotherGreeting(for: "Dave")) // Prints "Hello, Dave!"

func someFunction(firstParameterName: Int, secondParameterName: Int) { // In the function body, firstParameterName and secondParameterName // refer to the argument values for the first and second parameters. } someFunction(firstParameterName: 1, secondParameterName: 2)

func greet(person: String, from hometown: String) -> String { return "Hello \(person)! Glad you could visit from \(hometown)." } print(greet(person: "Bill", from: "Cupertino")) // Prints "Hello Bill! Glad you could visit from Cupertino."

func someFunction(_ firstParameterName: Int, secondParameterName: Int) { // In the function body, firstParameterName and secondParameterName // refer to the argument values for the first and second parameters. } someFunction(1, secondParameterName: 2)

func someFunction(parameterWithoutDefault: Int, parameterWithDefault: Int = 12) { // If you omit the second argument when calling this function, then // the value of parameterWithDefault is 12 inside the function body. } someFunction(parameterWithoutDefault: 3, parameterWithDefault: 6) // parameterWithDefault is 6 someFunction(parameterWithoutDefault: 4) // parameterWithDefault is 12

func arithmeticMean(_ numbers: Double...) -> Double { var total: Double = 0 for number in numbers { total += number } return total / Double(numbers.count) } arithmeticMean(1, 2, 3, 4, 5) // returns 3.0, which is the arithmetic mean of these five numbers arithmeticMean(3, 8.25, 18.75) // returns 10.0, which is the arithmetic mean of these three numbers

func swapTwoInts(_ a: inout Int, _ b: inout Int) { let temporaryA = a a = b b = temporaryA }

var someInt = 3 var anotherInt = 107 swapTwoInts(&someInt, &anotherInt) print("someInt is now \(someInt), and anotherInt is now \(anotherInt)") // Prints "someInt is now 107, and anotherInt is now 3"

var someInt = 3 var anotherInt = 107 swapTwoInts(&someInt, &anotherInt) print("someInt is now \(someInt), and anotherInt is now \(anotherInt)") // Prints "someInt is now 107, and anotherInt is now 3"

func addTwoInts(_ a: Int, _ b: Int) -> Int { return a + b } func multiplyTwoInts(_ a: Int, _ b: Int) -> Int { return a * b }

func printHelloWorld() { print("hello, world") }

var mathFunction: (Int, Int) -> Int = addTwoInts

print("Result: \(mathFunction(2, 3))") // Prints "Result: 5"

let anotherMathFunction = addTwoInts // anotherMathFunction is inferred to be of type (Int, Int) -> Int

func printMathResult(_ mathFunction: (Int, Int) -> Int, _ a: Int, _ b: Int) { print("Result: \(mathFunction(a, b))") } printMathResult(addTwoInts, 3, 5) // Prints "Result: 8"

func stepForward(_ input: Int) -> Int { return input + 1 } func stepBackward(_ input: Int) -> Int { return input - 1 } func chooseStepFunction(backward: Bool) -> (Int) -> Int { return backward ? stepBackward : stepForward } var currentValue = 3 let moveNearerToZero = chooseStepFunction(backward: currentValue > 0) // moveNearerToZero now refers to the stepBackward() function print("Counting to zero:") // Counting to zero: while currentValue != 0 { print("\(currentValue)... ") currentValue = moveNearerToZero(currentValue) } print("zero!") // 3... // 2... // 1... // zero!

func chooseStepFunction(backward: Bool) -> (Int) -> Int { func stepForward(input: Int) -> Int { return input + 1 } func stepBackward(input: Int) -> Int { return input - 1 } return backward ? stepBackward : stepForward } var currentValue = -4 let moveNearerToZero = chooseStepFunction(backward: currentValue > 0) // moveNearerToZero now refers to the nested stepForward() function while currentValue != 0 { print("\(currentValue)... ") currentValue = moveNearerToZero(currentValue) } print("zero!") // -4... // -3... // -2... // -1... // zero!