我是否使用C#动态实现了Y-combinator,如果没有,那么它是什么？

using System;

delegate Func<A, R> RecursiveFunc<A, R>(Func<A, R> f);

class Program
{
    static Func<A, R> Y<A, R>(RecursiveFunc<A, R> f)
    {
        Func<Func<A, R>, Func<A, R>> g = (Func<A, R> h) =>
        {
            return (A x) => h(h)(x);
        };
        return g(f(g(f)));
    }

    static Func<int, int> factorial = Y<int, int>(fact => n =>
    {
        if (n == 0) return 1;
        else return n * fact(n - 1);
    });

    static void Main(string[] args)
    {
        Console.WriteLine(factorial(5)); // 输出 120
    }
}