using System;

using System.Linq;

using System.Collections.Generic;

​

// Basic filter works like so:

// Filter(new int[] {1,2,3,4}, (Func<int,bool>)(input => input > 2))

// --> [3,4]

​

// Basic reduce works like so:

// Reduce(new int[] {1,2,3,4}, (acc,input) => acc+input)

// --> 10

​

public class Program {

    public static int[] filter(int[] n, Func<int, bool> fn){

        List<int> result = new List<int>();

        foreach(var i in n){

            if(fn(i)) result.Add(i);

        }

        return result.ToArray();

    }

    public static int reduce(int[] n, Func<int, int, int> fn) {

        int result = 0;

        foreach(var i in n) 

            result = fn(result, i);

        return result;

    }

    public static void Main(){

        int[] x = {1,2,3,4};

        Func<int, bool> f = v => v > 2;

        foreach(var i in filter(x, f)) Console.WriteLine(i);

        Func<int, int, int> r = (acc,v) => acc+v;

        Console.WriteLine(

            reduce(x, r) == 10

        );

    }

}

​

​