Jump Statements

class TicTacToe     // Declares the TicTacToe class.
{
    static void Main()      // Declares the entry point of the program.
    {
       int winner=0;
       // Stores locations each player has moved.
       int[] playerPositions = {0,0};

       // Hardcoded board position
       // X | 2 | O
       // ---+---+---
       // O | O | 6
       // ---+---+---
       // X | X | X
       playerPositions[0] = 449;
       playerPositions[1] = 28;

       // Determine if there is a winner
       int[] winningMasks = {
                  7, 56, 448, 73, 146, 292, 84, 273 };

       // Iterate through each winning mask to determine
       // if there is a winner.
       foreach(int mask in winningMasks)                                    
       {                                                                    
             if ((mask & playerPositions[0]) == mask)
             {
                   winner = 1;
                   break;                                                   
             }
             else if ((mask & playerPositions[1]) == mask)
             {
                   winner = 2;
                   break;                                                   
             }
 }                                                                          

 System.Console.WriteLine(
      "Player {0} was the winner", winner);
}
}

Player 1 was the winner

Beginner Topic: Bitwise Operators for Positions

The tic-tac-toe example (Appendix B) uses the bitwise operators to determine which player wins the game. First, the code saves the positions of each player into a bitmap called playerPositions. (It uses an array so that the positions for both players can be saved.)

To begin, both playerPositions are 0. As each player moves, the bit corresponding to the move is set. If, for example, the player selects cell 3, shifter is set to 3 1. The code subtracts 1 because C# is zero based and you need to adjust for 0 as the first position instead of 1. Next, the code sets position, the bit corresponding to cell 3, using the shift operator 000000000000001 << shifter, where shifter now has a value of 2. Lastly, it sets playerPositions for the current player (subtracting 1 again to shift to zero based) to 0000000000000100. Listing 3.48 uses |= so that previous moves are combined with the current move.

Setting the Bit That Corresponds to Each Player's Move

int shifter;  // The number of places to shift
                                                 // over in order
 to set a bit.
int position; // The bit which is to be set

// int.Parse() converts "input" to an integer.
// "int.Parse(input) 1" because arrays
// are zero based.
shifter = int.Parse(input)- 1;

// Shift mask of 00000000000000000000000000000001
// over by cellLocations.
position = 1 << shifter;
// Take the current player cells and OR them to set the
// new position as well.
// Since currentPlayer is either 1 or 2,
// subtract one to use currentPlayer as an
// index in a 0-based array.
playerPositions[currentPlayer-1] |= position;

Later on in the program, you can iterate over each mask corresponding to winning positions on the board to determine if the current player has a winning position, as shown in Listing 3.47.

class EmailDomain
{
 static void Main()
 {

  string email;
  bool insideDomain = false;
  System.Console.WriteLine("Enter an email address: ");

  email = System.Console.ReadLine();

  System.Console.Write("The email domain is: ");

  // Iterate through each letter in the email address.
  foreach (char letter in email)
  {
      if (!insideDomain)
      {
        if (letter == '@')
        {
           insideDomain = true;
        }
        continue;
      }

      System.Console.Write(letter);
   }
  }
}

Enter an email address:
mark@dotnetprogramming.com
The email domain is: dotnetprogramming.com

foreach (char letter in email)
{
   if (insideDomain)
   {
          System.Console.Write(letter);
   }
   else
   {
          if (letter == '@')
          {
              insideDomain = true;
          }
    }
}

// ...
static void Main(string[] args)
{
 bool isOutputSet = false;
 bool isFiltered = false;

 foreach (string option in args)
 {
     switch (option)
     {
         case "/out":
             isOutputSet = true;
             isFiltered = false;
             goto default;                                                   
         case "/f":
             isFiltered = true;
             isRecursive = false;
             goto default;                                                   
         default:
             if (isRecursive)
             {
                   // Recurse down the hierarchy
                   // ...

             }
             else if (isFiltered)
             {
                // Add option to list of filters.
                // ...
             }
             break;
      }
  }
  // ...
}

C:\SAMPLES>Generate /out fizbottle.bin /f "*.xml" "*.wsdl"