extension Int: ExampleProtocol {
    var simpleDescription: String {
        return "The number (self)"
    }
    mutating func adjust() {
        self += 42
    }
}
7.simpleDescription

7.adjust()

Immutable value of type `Int` only has mutating members named adjust.

var myNum = 7
myNum.adjust()
println(myNum) // 49