using System;

public class Program

{

    public static void Main()

    {

        var items = new int[5];

        Console.WriteLine("\nWraping any numbers");

        for(var i = -6; i < 7; i++)

        {

            var idx = ArrayUtils.WrapIndex(i, items);

            Console.WriteLine(i + " -> " + idx);

        }

        Console.WriteLine("\ngoing backward with step size 1");

        var current = 0;

        for(var i = 10; i > 0; i--)

        {

            ArrayUtils.Backward(ref current, items, 1);

            Console.WriteLine("current =" + current);

        }

        Console.WriteLine("\ngoing forward with step size 3");

        for(var i = 10; i > 0; i--)

        {

            ArrayUtils.Forward(ref current, items, 3);

            Console.WriteLine("current =" + current);

        }

    }

​

    public static class ArrayUtils

    {

    public static void Forward<T>(ref int currentIndex, T[] array, int amount)

    {

        currentIndex = WrapIndex(currentIndex + amount, array);

    }

    public static void Backward<T>(ref int currentIndex, T[] array, int amount)

    {

        currentIndex = WrapIndex(currentIndex - amount, array);

    }

    public static int WrapIndex<T>(int newIndex, T[] array)

    {

        var length = array.Length;

        return ((newIndex % length) + length) % length;

    }

}}