import Foundation

func noArgumentAndNoReturnValue() {
    "I don't know what I'm doing"
}

noArgumentAndNoReturnValue()

func plusTwo(value: Int) {
    let newValue = value + 2
}

plusTwo(value: 30)

func newPlusTwo(value: Int) -> Int {
    return value + 2
}

newPlusTwo(value: 30)

func customAdd(value1: Int, value2: Int) -> Int {
    value1 + value2
}

let customAdded = customAdd(value1: 10, value2: 30)

// function(external internal: Type) -> Type
func customMinus(_ lhs: Int, _ rhs: Int) -> Int {
    lhs - rhs
}

customMinus(10, 2)

customAdd(value1: 20, value2: 60)

@discardableResult
func myCustomAdd(_ lhs: Int, _ rhs: Int) -> Int {
    lhs + rhs
}

func doSomethingComplicated(with value: Int) -> Int{
    func mainLogic(value: Int) -> Int {
        value + 2
    }
    
    return mainLogic(value: value + 3)
}

doSomethingComplicated(with: 10)

func getFullName(
    firstName: String = "Foo",
    lastName: String = "Bar"
) -> String {
    "\(firstName) \(lastName)"
}

getFullName()
getFullName(firstName: "Gary")
getFullName(lastName: "Gan")
getFullName(firstName: "Gary", lastName: "Gan")