using System;

​

public class Program

{

    public static void Main() {

        var maybe = Maybe<int>.From(10);

​

        var maybe2 = Bind(maybe, a => Maybe<string>.From(a.ToString()));

    }

​

    static IMonad<K, B> Bind<T, K, A, B>(IMonad<T, A> monad, Func<A, IMonad<K, B>> binder) {

        return monad.Bind(binder);

    }

​

    abstract class AbstractMonad<T, A> : IMonad<T, A>

    {

        protected A value;

​

        public abstract IMonad<K, B> Bind<K, B>(Func<A, IMonad<K, B>> binder);

        public abstract IMonad<T, A> Return(A a);

    }

​

    class Maybe<A> : AbstractMonad<Maybe<A>, A>

    {   

        public static Maybe<A> From(A a) {

            return new Maybe<A>(a);

        }

​

        private Maybe(A a) {

            value = a;

        }

​

        public override IMonad<K, B> Bind<K, B>(Func<A, IMonad<K, B>> binder) {

            return binder(value);

        }

​

        public override IMonad<Maybe<A>, A> Return(A a) {

            return new Maybe<A>(a);

        }

    }

​

​

    interface IMonad<T, A>

    {

        IMonad<K, B> Bind<K, B>(Func<A, IMonad<K, B>> binder);

        IMonad<T, A> Return(A a);

    }

​

}

​

​