using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {

            IEnumerable<String> enu = new String[] {"koko", "kol"};
            enu.IsEmpty();
            enu.MeanLength();

            IEnumerable<float> floatt = new float[] { 2.3f, 4.5f};
            floatt.IsEmpty();
            floatt.Mean();

            IEnumerable<int> intt = new int[] {};
            intt.IsEmpty();
            intt.Mean();


            Console.ReadKey();
        }
    }

    static class Rozszerzajaca
    {

        public static bool IsEmpty(this IEnumerable source)
        {
            if (source != null && source.GetEnumerator().MoveNext())
            {

                Console.WriteLine("IsEmpty: Not Empty!");
                return false;

            }
            else
            {
                Console.WriteLine("IsEmpty: Empty!");
                return true;
            }

        }

        public static void Mean(this IEnumerable<float> source)
        {
            if (source != null && source.GetEnumerator().MoveNext())
            {

                float sum = 0;
                int il = 0;
                foreach (float i in source)
                {
                    sum = sum + i;
                    il++;
                }

                float res = sum / il;
                Console.WriteLine("Mean: " + res);
            }
            else
                Console.WriteLine("Mean: Empty array!");

        }


        public static void Mean(this IEnumerable<int> source)
        {
            if (source != null && source.GetEnumerator().MoveNext())
            {
                double sum = 0;
                int il = 0;
                foreach (int i in source)
                {
                    sum = sum + i;
                    il++;
                }

                double res = sum / il;
                Console.WriteLine("Mean: " + res);
            }
            else
                Console.WriteLine("Mean: Empty array!");



        }

        public static void MeanLength(this IEnumerable<string> source)
        {
            if (source != null && source.GetEnumerator().MoveNext())
            {
                double sum = 0;
                int il = 0;
                foreach (var i in source)
                {
                    sum = sum + i.Length;
                    il++;
                }
                double res = sum / il;
                Console.WriteLine("Mean length: " + res);
            }
            else
                Console.WriteLine("Mean length: Empty array!");

        }

    }
}