module Id;

data Nat = Zero | S(Nat);

def B iter<A,B>(f, g)(Nat x) =
    case x {
    Zero => g;
    S(xP) => f(iter(xP));
};

def B compS<B>(f)(Nat z) = f(S(z));

def A id<A>(A y) = y;

// type A as function?
def Nat iterid<A>(Nat n) =
    let (A f) = iter(compS, id)(n)
    in f(Zero);


def Nat start(Nat n) = iterid(n);

{

}