infix operator ***: MultiplicationPrecedence
infix operator +++: AdditionPrecedence

func ***(x: Int, y: Int) -> String {
    print("f1")
    return ""
}

func ***(x: Int, y: Int) -> Int {
    print("f2")
    return 0
}

func +++(x: String, y: Int) -> Int {
    print("f3")
    return 0
}

func +++(x: Int, y: Int) -> Int {
    print("f4")
    return 0
}

let result = 0 *** 4 +++ 0      // prints f2 and f4