Repeater function in Swift

repeater.swift

// Runs in a Playground

func repeat(function: () -> (), untilNoChangeTo sentinel: () -> String) {
    var initial, final: String
    
    do {
        initial = sentinel()
        function()
        final = sentinel()
    } while initial != final
}

func repeatGenerically<T: Equatable>(function: () -> (), untilNoChangeTo sentinel: () -> T) {
    var initial, final: T
    
    do {
        initial = sentinel()
        function()
        final = sentinel()
    } while initial != final
}

class Repeater {
    var count = 0
    let target: Int
    
    init(count: Int, target: Int) {
        self.count = count
        self.target = target
    }
    
    func increment() {
        if count < target {
            ++count
        }
    }
    
    func countAsString() -> String {
        return "\(count)"
    }
    
    func countAsDouble() -> Double {
        return Double(count)
    }
}

let rep1 = Repeater(count: 0, target: 5)
let rep2 = Repeater(count: 0, target: 5)

repeat(rep1.increment, untilNoChangeTo: rep1.countAsString)
repeatGenerically(rep2.increment, untilNoChangeTo: rep2.countAsDouble)

println(rep1.count)
println(rep2.count)