linq monad

linqMonad.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using Monad;
using System.Collections;

namespace Monad
{
    public class Maybe<T>
    {
        public readonly static Maybe<T> Nothing = new Maybe<T>();
        public T Value { get; private set; }
        public bool HasValue { get; private set; }
        Maybe()
        {
            HasValue = false;
        }
        public Maybe(T value)
        {
            Value = value;
            HasValue = true;
        }
    }

    public static class Helpers//monad in linq
    {
        public static Maybe<T> ToMaybe<T>(this T value)
        {
            return new Maybe<T>(value);
        }

        public static Maybe<U> SelectMany<T, U>(this Maybe<T> m, Func<T, Maybe<U>> k) //bind
        {
            if (!m.HasValue)
                return Maybe<U>.Nothing;
            return k(m.Value);
        }

        public static Maybe<V> SelectMany<T, U, V>(
        this Maybe<T> id,
        Func<T, Maybe<U>> k,
        Func<T, U, V> s)
        {
            return id.SelectMany(x => k(x).SelectMany(y => s(x, y).ToMaybe()));
        } 
    }
    


    class Program
    {
        static void Main(string[] args)
        {
            //list monad
            var result2 = from x in new List<int> { 1, 2, 3 }
                          from y in new List<int> { 4, 5, 6 }
                            select Tuple.Create(x,y);
                
            //maybe monad
            var r = from x in 5.ToMaybe()
                    from y in Maybe<int>.Nothing
                    select x + y;

            Console.WriteLine(r.HasValue ? r.Value.ToString() : "Nothing");

            Console.ReadLine();
        }
    }
}