more_reader.cs

    public static class ReaderExtensions
    {
        public static Func<T, B> Select<T, A, B>(this Func<T, A> reader, Func<A, B> f)
        {
            return t => f(reader(t));
        }

        public static Func<T, B> SelectMany<T, A, B>(this Func<T, A> reader, Func<A, Func<T, B>> f)
        {
            return t =>f(reader(t))(t);
        }

        public static Func<T, C> SelectMany<T, A, B, C>(this Func<T, A> reader, Func<A, Func<T, B>> f, Func<A, B, C> selector)
        {
            return reader.SelectMany(a => f(a).Select(b => selector(a, b)));
        }
    }

more_reader_contrived_examples.cs

    public class ReaderExamples
    {
        Func<int, int> add1 = x => x + 1;
        Func<int, string> show = x => x.ToString();
 
        [Test]
        public void Example1()
        {
            var incAndShow = add1.Select(show);
 
            Assert.AreEqual("2", incAndShow(1));
        }
 
        [Test]
        public void Example2()
        {
            var incAndShow = from next in add1
                             select show(next);
 
            Assert.AreEqual("2", incAndShow(1));
        }
 
        [Test]
        public void Example3()
        {
            var incAndShow = add1.SelectMany<int, int, string>(a => t => show(a));
 
            Assert.AreEqual("2", incAndShow(1));
        }
 
        [Test]
        public void Example4()
        {
            var incPlusShow = from next in add1
                              from shown in show
                              select (next + " " + shown);
 
            Assert.AreEqual("2 1", incPlusShow(1));
        }
    }