Computer Science Teacher
Computer Science Teacher - Thoughts and Information from Alfred Thompson

March, 2012

  • Computer Science Teacher - Thoughts and Information from Alfred Thompson

    ChronoZoom–a new way to look at history

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    Microsoft Research announced a new project a couple of days ago called ChronoZoom - An Infinite Canvas in Time and you can get full information at that link but the intro paragraph below is a bit of an idea of what this is about. I think this will be interesting to history teachers as well as computer science teachers.

    ChronoZoom is an open-source community project dedicated to visualizing the history of everything. Big History is the attempt to understand, in a unified, interdisciplinary way, the history of cosmos, Earth, life, and humanity. By using Big History as the story line, ChronoZoom seeks to bridge the gap between the humanities and sciences an enable all this information to be easily understandable and navigable.

    Get involved



  • Computer Science Teacher - Thoughts and Information from Alfred Thompson

    Pex4fun, an online lab for APCS

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    Are you teaching Advanced Placement Computer Science? Are you looking for supplemental exercises that may help you students with the concepts? If so this announcement may be of interest to you. Pex for Fun has been around for a while offering coding duels in C#, F# and Visual Basic. Recently though it was decided to invest some time, money and effort to adapt some exercises specifically to help learn APCS concepts. Most students find the differences between Java and C# pretty minor at this level so most APCS students will find this doable even if they have only been taught Java previously.

    Pex4fun APCS (http://pexforfun.com/apcs) is an online lab for APCS. It features 156 coding duels organized in chapters mapping the APCS program. In each coding duel, the student has to implement a program against a specification. At each attempt, pex4fun analyzes the student program together with the specification program to produce an input/output table showcasing cases where the behavior matches or not. Based on this feedback, the student can iteratively refine his solution until his program has the same observable behavior as the specification program.

    Pex4fun is free, runs in any browser and provides a rich auto-completion experience.

    clip_image002



  • Computer Science Teacher - Thoughts and Information from Alfred Thompson

    Tic Tac Toe for Windows Phone

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    Introduction

    imageWe are going to create a simple Tic Tac Toe game for Windows Phone. We’ll be using Visual Studio as our development environment and C# for our programming language. All the resources you need are listed below and all are free.

     

    Resources:

    Windows Phone Development SDK

    VISUAL STUDIO 2010 EXPRESS FOR WINDOWS PHONE http://www.microsoft.com/visualstudio/en-us/products/2010-editions/windows-phone-developer-tools  or http://bit.ly/ymbC9Q  

    Windows Phone for Absolute Beginners video series http://channel9.msdn.com/Series/Windows-Phone-7-Development-for-Absolute-Beginners  or http://bit.ly/x72NnV  

    Alfred Thompson’s blog http://blogs.msdn.com/b/alfredth/  or http://bit.ly/AlfredTh 

    For a copy of this post in Word format, the images for the project, and code snippets used to create this lab download the PhoneTTT.zip file from https://skydrive.live.com/?cid=9a87f3a86cb0aa3e&id=9A87F3A86CB0AA3E%215413

    Open Visual Studio

    Find Visual Studio on the Start menu and open it up. It should look something like this.

    Next we will open a new project. From the File menu select New Project. From the New Project form select Visual C# as the language Silverlight for Windows Phone under that and Windows Phone Application as the application type. Make sure you give your project a name. Something like TicTacToe followed by your initials will do nicely (TicTacToeACT)

     

    image

    image

    We’ll be using the latest Windows Phone Version which is 7.1.

    image

    Our initial screen will look something like this.

    image

    We’ll come back to this in a minute.

    Add Image Resources

    We need to add some image files to the project. We will be adding images for an empty box , the letter O and the letter X.   Right click on the Solution in the Solution viewer and select Add > Existing Item. You can download them from here if you like.

    imageimageempty

     

     

    image

    Browse to where the files for the project are (should be on the Desktop) and select the three files we need and click on add.

    image

    Design Our Form

    Now let’s go back to designing our form on the mock up of the phone.  Left  click on where it says “page name” and select properties. The properties window will open up and we will change the Text property to Tic Tac Toe.

    imageimage

    Next we will use the Tool box and drag an Image onto the form.

    imageimage

    Using the properties form set the Height to 69, the width to 93 and the Source to the image file of the empty box. Use copy and paste to make a series of identical image boxes on the form. The results should look something like the image above.

    Add a tenth copy below the ninth copy. Next to that draw a Text Block. Change the Text property of the Text Block  to read “Next Move.” You may want to play with the font size property as well. The result will look something like this.

    image

    We’ll come back to this but now let us enter some code.

    Declare some variables

    Under MainPage.xaml on the Solution Explorer you will find MainPage.xaml.cs which hold our programming code. Double click on that to open the code editing window.

    image

    Above the constructor declare some variables that we will use to manage the game throughout the program.

    public partial class MainPage : PhoneApplicationPage
     {
     
     
         // Boolean variables to track whose move it is and if the game is over
         Boolean isX, GameOver;
         // An array to track the contents of each box (0 = empty 1 = X 2 = O)
         int[] boxValue;
         // Helpful images
         Image myXImage, myOimage, myEmptyImage;
         // Counting moves
         int MoveCount;
                 
         // Constructor
         public MainPage()

    Initialize Variables

    Inside the constructor we will set the initial values of our variables.

    Note that the resetBoxes method has not been created yet so the IDE gives us a warning. (The same sort of red squiggly live we are used to from Microsoft Word) Let’s correct that now. Also note that a common cause of problems is the wrong location in the Uri section. Change the “TicTacToe” in this sample code to match your project name.

    // Constructor
    public MainPage()
    {
        InitializeComponent();
     
     
        boxValue = new int[10];
        // STore the images for use in the game
        myXImage = new Image();
        myXImage.Source = new System.Windows.Media.Imaging.BitmapImage(new Uri("/PhoneApp3;component/x.jpg", UriKind.RelativeOrAbsolute));
        myOimage = new Image();
        myOimage.Source = new System.Windows.Media.Imaging.BitmapImage(new Uri("/PhoneApp3;component/o.jpg", UriKind.RelativeOrAbsolute));
        myEmptyImage = new Image();
        myEmptyImage.Source = new System.Windows.Media.Imaging.BitmapImage(new Uri("/PhoneApp3;component/empty.jpg", UriKind.RelativeOrAbsolute));
        // Set the initial state of the game board
        resetBoxes();
            
    }

    Create a Method to Set the Game Board

    Our method here will have to initialize some additional variables. We do it here so that we can reset them all in just one place when we start new games.

     
            // Set the initial state of the game board
            void resetBoxes()
            {
     
                GameOver = false;
                MoveCount = 0;
     
                isX = true;
                // Set all boxes to empty
                for (int i = 0; i < 10; i++)
                    boxValue[i] = 0;
                // Display empty images in all boxes on screen
                image1.Source = myEmptyImage.Source;
                image2.Source = myEmptyImage.Source;
                image3.Source = myEmptyImage.Source;
                image4.Source = myEmptyImage.Source;
                image5.Source = myEmptyImage.Source;
                image6.Source = myEmptyImage.Source;
                image7.Source = myEmptyImage.Source;
                image8.Source = myEmptyImage.Source;
                image9.Source = myEmptyImage.Source;
                GameOver = false;
                MoveCount = 0;
                textBlock1.Text = "Next Move ";
                image10.Source = myXImage.Source;
     
            }

    Respond to Taps

    We’ll play the game by tapping on individual boxes. For each tap we have to make sure it is a valid move (nothing in the box already), store and display the right symbol and check for a win or a tie. We’ll need a tab routine for each box but I’m only going to show one of them here. The rest is left as an exercise for the student. J

    As you can see this method calls several of the methods we have not yet created. Let’s get on that.

    // Respond to taps on all boxes.
    // For each box:
    // Check that it is empty and only act if it is
    // Call UpdateBox to record move and return which symbol to display
    // Check for a winner
    private void image9_Tap(System.Object sender, System.Windows.Input.GestureEventArgs e)
    {
        if (boxValue[9] == 0)
        {
            boxValue[9] = updateBox();
            if (boxValue[9] == 1)
            {
                image9.Source = myXImage.Source;
            }
            else
            {
                image9.Source = myOimage.Source;
            }
            if (IsWinner())
                endGame();
        }
    }

    Updating a Box

    // Count move and determine which player made the move.
    // Display the symbol for the next player to move
    public int updateBox()
    {
        if (GameOver)
            return 0;
        MoveCount = MoveCount + 1;
     
        if (isX)
        {
            isX = !isX;
            image10.Source = myOimage.Source;
            return 1;
        }
        else
        {
            isX = !isX;
            image10.Source = myXImage.Source;
            return 2;
        }
     
    }

    Checking for a Winner

    Checking for a winner means looking for three boxes in a row, column or diagonal that have the same value. Oh and it has to be the same not empty box value.

    Getting close now. Notice the call to TieGame? Let’s create that routine after we create the winning end of a game.

    // Determine if there is a winner by checking possible winning combinations
        private bool IsWinner()
        {
            bool HaveWinner = false;
            HaveWinner = false;
            if (boxValue[1] != 0 & boxValue[1] == boxValue[2] & boxValue[1] == boxValue[3])
                HaveWinner = true;
            if (boxValue[4] != 0 & boxValue[4] == boxValue[5] & boxValue[4] == boxValue[6])
                HaveWinner = true;
            if (boxValue[7] != 0 & boxValue[8] == boxValue[7] & boxValue[7] == boxValue[9])
                HaveWinner = true;
            if (boxValue[1] != 0 & boxValue[1] == boxValue[4] & boxValue[4] == boxValue[7])
                HaveWinner = true;
            if (boxValue[2] != 0 & boxValue[2] == boxValue[5] & boxValue[5] == boxValue[8])
                HaveWinner = true;
            if (boxValue[3] != 0 & boxValue[6] == boxValue[3] & boxValue[6] == boxValue[9])
                HaveWinner = true;
            if (boxValue[1] != 0 & boxValue[1] == boxValue[5] & boxValue[5] == boxValue[9])
                HaveWinner = true;
            if (boxValue[3] != 0 & boxValue[3] == boxValue[5] & boxValue[5] == boxValue[7])
                HaveWinner = true;
     
            if (HaveWinner == true)
                GameOver = true;
            // if there is no winner but we have taken 9 moves declare a draw (tie)
            if (MoveCount >= 9)
                TieGame();
            return HaveWinner;
        }

    Handling the End of a Game

    Here we have the two routines that show the end of a game. One for a winning game and one for a tie game.

    // Announce the winner
          public void endGame()
          {
              textBlock1.Text = "The Winner is";
              if (isX)
              {
                  image10.Source = myOimage.Source;
              }
              else
              {
                  image10.Source = myXImage.Source;
              }
          }
                  
     
          // Display tie game information
          public void TieGame()
          {
              image10.Source = myEmptyImage.Source;
              textBlock1.Text = "Tie Game";
     
          }

    We just have two more things to do. The first of those is that we have to “tell” the image boxes to call the tap routines when they are tapped. For this we go back to the design window.

    Assigning Tap Handlers

     

    Back on the property window you will find the Events tab. Selecting that and moving down we find an option for Tap.  Selecting each image one by one we can use the drop down list to set the right handler for each image box.

    image

    Starting a New Game

    All we need now is a way to start a new game. I suggest we tap on the Text Block to do that. Select the Text Block and in the properties window option for Tap enter New Game and press the enter key. This will open up the code window with a chance for use to call the ResetBoxes method we created.

    private void NewGame(object sender, GestureEventArgs e)
    {
        resetBoxes();
    }

    Testing

    Ok let’s run it and see how we did.



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