Swift Church Encoding. Barely.

gistfile1.swift

typealias ø = ((Int -> Int) -> Int -> Int)

func i<T>(v :T) -> T {
    return v
}

func c<T>(n: Int) -> (T -> T) -> T -> T {
    if n == 0 {
        return { x in i }
    }
    return { (𝑓 : (T -> T)) -> T -> T in
        return { x in
            return 𝑓(c(n - 1)(𝑓)(x))
        }
    }
}

func u<T>(f : ((Int -> Int) -> Int -> T)) -> T {
    return f({ (i : Int) -> Int in
        return i + 1
    })(0)
}

let o :ø = c(0)
let e :ø = c(1)
let ee :ø = c(2)
let eee :ø = c(3)

u(e)    // 1
u(ee)   // 2
u(eee)  // 3
u(c(4)) // 4
u(c(5)) // 5