Lambda Expressions Are Cool, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

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

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            //Map() takes a function and applies it to each element in the array
            int[] data = new int[] {0,1,2,3,4,5};
            Console.WriteLine(data.ArrayString());
            data = data.Map(i => i * i); //note that if the only thing you're doing is returning a value,
            //you don't need a return expression or curly brackets.
            //if there is more than one parameter you need to surround them with parentheses. the types of these do not USUALLY need to be typed.
            Console.WriteLine(data.ArrayString());
            
            bool[] bools = new bool[] {true,false,true,false};
            Console.WriteLine(bools.ArrayString());
            bools = bools.Map(b => !b);
            Console.WriteLine(bools.ArrayString());
            
            
            //Another example of lambda, declaring a local function within a function
            Func<int,bool> positive = i => {Console.WriteLine(i); return i > 0;};
            Console.WriteLine(positive(5));
            Console.WriteLine(positive(-5));
            //You could declare the same function the regular way like this:
            //public bool positive(int i) 
            //{
            //    Console.WriteLine(i);
            //    return i > 0;
            //} 
            //(not inside of another function, though)
            
            //Void lambda, second Map() override
            string message = "Hello World!";
            message.ToCharArray().Map(c => {
                Console.Write(((int)c).ToString() + ":");
                Console.Write(c.ToString());
                Console.Write(",");
            });
            
            //...and you can put more than one parameter into a lambda expression, but because you need a delegate for each number of parameters, I'm just going to write a long comment about it.
            //if you have a delegate declared like "public delegate int intwoints(int a, int b);", then the lambda expression would be:
            //"intwoints example = (a,b) => a + b;" or something.
            //note that like passing parameters into a regular func you can name a and b whatever you want, just remeber to use those names in the body of your lambda.
            
            
            
            //I'm new to this tutorial thing so if there's something that's wrong or you didn't like here just tell me, thanks
        }
    }
    static class Extn
    {
        public delegate T2 Func<T1,T2>(T1 p); //replacing Func<> provided in VS
        public delegate void Action<T>(T p); //replacing Action<> provided in VS
        public static T[] Map<T>(this T[] a, Func<T,T> f)
        {
            T[] res = a;
            for(int x = 0; x < res.Length; x++) res[x] = f(res[x]);
            return res;
        }
        public static string ArrayString<T>(this T[] a) //prints out an array in "human-readable" format
        {
            string tor = "[";
            foreach(T t in a) tor += t.ToString() + ",";
            return tor.Remove(tor.Length - 1) + "]";
        }
        public static void Map<T>(this T[] a, Action<T> f)
        {
            foreach(T t in a) f(t);
        }
    }
}

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Compilation time: 0,17 sec, absolute running time: 0,09 sec, cpu time: 0,09 sec, average memory usage: 17 Mb, average nr of threads: 3