How does C# Evaluate an array loop Boolean equilancy?

Question

I'm trying to figure out why in the following method the last value in the array '8' would fulfill the where clause of "(8 & 7) == 0."

public class Test {
      public static void Main() {
             int[] Arr = {-3, -1, 0, 1, 3, 8};
             var s = from x in Arr where (x & (x-1)) == 0 select x+1;
             foreach (int x in s)
                    Console.Write(x + " ");
      } 
}

It's included on a recruitment skills test, and for the life of me I can't figure out why that value is selected. Either way I won't be using it on my tests, but I'm curious since I've never run across this before.

Answer 1

So a single & is a bitwise operator. It's looking at those numbers binary representation.

7 = 0111 and 8 = 1000

When you combine them you get 0.

That is why your method prints out a 9.