module ListRev1;


// let comp f g = fun z -> f (g z);;

// def B comp<A, B>(f,g)() = (A z) => f(g(z)); // Error
def B comp<A, B>(f,g)(A z) = f(g(z));

// let rev1 l =
//   let rec walk = function
//   [] -> (fun ys -> ys)
//     | x :: xs -> comp (walk xs) (fun ys -> x :: ys)
//   in walk l [];;

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

def List<A> walk<A>(List<A> l) =
    case l {
    Nil => id;
    Cons(x,xs) => comp((walk(xs)), ((List<A> ys) => Cons(x, ys)));
}

def List<A> rev1<A>(List<A> l) = walk(l, Nil);


def List<A> start<A>(List<A> l) = rev1(l);

{


}