using System;

using System.Collections.Generic;

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using MyNamespace;

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namespace DailyQuiz

{

public class Program

{

    public static void Main()

    {

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           IEnumerable<string> cities = new[] {"al", "be", "de", "ga", "la", "lu"};

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           var query =

               cities.Filter(StringStartsWithL);

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           foreach (var city in query)

           {

               Console.WriteLine(city);   

           }

​

​

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    }

​

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        static bool StringStartsWithL(string s)

        {

            return s.StartsWith("l");

        }

​

​

​

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}

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}

​

​

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namespace MyNamespace

{

    public static class FilterExtensions

    {

        public static IEnumerable<T> Filter<T> (this IEnumerable<T> input, 

        Func<T, bool> predicate )

        {

            foreach (var item in input)

            {

                if (predicate(item))

                {

                    yield return item;

                }

            }       

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        }

​

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    }

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}

​

​

​