Rx/CSharp Scan function example

cs

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

namespace SplitObservableTest
{
    class Program
    {
        static void Main(string[] args)
        {
            List<String> values = new List<string>()
            {
                "1", "2", "3",
                "a", "5", "6", "b", 
                "8", "9", "10", "11",
                "a", "13", "14", "b",
                "16", "17", "18", "19",
                "a", "21", "22", "b",
                "24"
            };
            var toDel = "<del>";
            // If we find an 'a' then we begin marking for deletion (return 'toDel').
            // Once we find a 'b' we stop marking for deletion (return an emtpy string).
            // If we are not deleting then return the value.  Otherwise return acc 
            // (which should be 'toDel').
            Func<string, string, string> scanFunc = (acc, val) =>
            {
                if (val == "a") return toDel;
                else if (val == "b") return "";
                else if (acc != toDel) return val;
                else return acc;
            };
            Func<string, bool> filterFunc = (val) =>
            {
                return val != toDel; // && val != ""; uncomment to get rid of empty lines
            };

            var dd = values.ToObservable()
                .Scan("", scanFunc)
                .Where(filterFunc)
                ;
            dd.Subscribe(s => Console.WriteLine(s));
        }
    }
}