Cont monad in C#, C#

Language: Layout:

// Cont monad in C#.
//Rextester.Program.Main is the entry point for your code. Don't change it.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public delegate TR Cont<TA, TR>(Func<TA, TR> c);
    public static class LinqContMonad
    {
        public static Cont<TU, TR> Select<TA, TR, TU>(this Cont<TA, TR> p, Func<TA, TU> selector)
        {
                return c => p(a => c(selector(a)));
        }

public static Cont<TV, TR> SelectMany<TA, TR, TU, TV>(
                this Cont<TA, TR> p,
                Func<TA, Cont<TU, TR>> selector,
                Func<TA, TU, TV> projector)
        {
                return c => p(a => selector(a)(u => c(projector(a, u))));
        }
    }
    
    public class Program
    {
        public static void Main(string[] args)
        {
            Cont<int, string> ex1 =
                from a in (Cont<int, string>)(c => c(1))
                from b in (Cont<int, string>)(c => c(10))
                select a + b;
            // result1 == "11"
            string result1 = ex1(x => x.ToString());
            Console.WriteLine(result1);

Cont<int, string> ex2 =
                from a in (Cont<int, string>)(c => c(1))
                from b in (Cont<int, string>)(fred => "escape")
                select a + b;
            // result2 == "escape"
            string result2 = ex2(x => x.ToString());
            Console.WriteLine(result2);

Cont<int, string> ex3 =
                from a in (Cont<int, string>)(c => c(1))
                from b in (Cont<int, string>)(fred => fred(10) + fred(20) )
                select a + b;
            // result3 == "1121"
            string result3 = ex3(x => x.ToString());
            Console.WriteLine(result3);
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0.26 sec, absolute running time: 0.11 sec, cpu time 0.09 sec, average memory usage: 14 Mb, average nr of threads: 4