CPSC120A
Fundamentals of Computer Science I

Lab 15

Logical Operators

Practice 1

Write a function compute_value(x), which uses a single if statement to determine what value to return. This function should return the value of x if \( 0 < x < 10\). Otherwise, your program should return 0. 
















  
Practice 2



Write a function omit_values(x), which uses a single if
statement to determine what value to return.  This function should
return the value of x as long as x is even
or x is negative.  Otherwise, your program should return 0.


  

    
  

  

    
  

  





The Return of the Bouncing Image



  The bouncing image screen saver you created in the last lab only
  moved horizontally.  A better animation is one that bounces all over
  the screen.  Using logical operators, you can create this animation.




Details



  Create a program that animates a bouncing image in a file
  called bouncing.py.  The image should begin in the center
  of the window and move diagonally.  When the image hits an edge of
  the window, it should bounce.  The animation should continue until
  the end of the animation loop.  Your program should only have
  two conditional statements.




Example


  $ python3 bouncing.py





Hint



  
  

    

      Look back at your bouncing ball program from the last lab.  This
      program will have the same overall structure.  Some things that
      are different:
    

    
    
      
  • 
        The image should have two variables controlling its speed.
        One for the x speed and one for the y speed.  These
        should be used in conjunction with an accumulator to change
        the position of the image every iteration of the loop.
      
    • 
      
  • 
        Making the image bounce is a matter of changing the image's
        direction.  The x speed and y speed variables control
        the image's direction.
      
    • 
      
  • 
        
    
          Only one speed variable needs to change when the image hits an
          edge.  For example when the ball hits the bottom edge:
        
    
        
        
    
          Only the y speed changes, and it changes sign, not magnitude.
        
    
      
    • 
      
  • 
        When the image hits the top and the bottom of the window, only
        the y speed changes and it changes in the same way, by
        changing sign.  If it is positive it becomes negative; if it
        is negative it becomes positive.  The x speed changes in
        the same way, when it hits the right or left sides.  This
        means that you only need two if statements to get the image to
        bounce, one for the top and bottom and one for the left and
        right.  Use a logical operator to create each of these
        conditional statements.
      
    • 
    

  




Pong



  One of the first successful video games was Pong. Back in the 1970's
  a game of Pong was so complicated that devices were sold that played
  only Pong. Today, Pong is the "Hello World" version of a video game;
  Its typically the first one you write. Today you are going to
  create a 1-player version of Pong.




Details



  Copy the program from the previous activity into a file
  called pong.py.  Modify the program to add a user
  controlled image.  The image should always be at or near the bottom
  of the window.  The image should be able to move only left and right
  in response to keyboard or mouse input.




  Modify the program so that the image bounces off of the player
  controlled image but does not bounce off of the bottom of the
  window.




Example


  $ python3 pong.py





Hint



  
  

    
Testing if the bottom of the ball hits the top of the paddle
      requires testing for three different conditions:
    

    
    
      
  1. 
        The bottom of the ball must be below the top of the rectangle.
      
    2. 
      
  2. 
        The center of the ball must be to the right of the rectangle's
        left side.
      
    3. 
      
  3. 
        The center of the ball must be to the left of the rectangle's
        right side.
      
    4. 
    

    
    

      Use logical operators to test if all three of these conditions
      are true..
    

  






  
Challenge 1

  

    The original Pong game was meant to be like ping-pong and you need
    two players to play ping-pong.  Modify the program so that it is a
    two player game.  Add a second user controlled image to the
    opposite side of the screen.
  






  
Challenge 2

  

    Modify the program so that it keeps score.  Every time the ball
    goes off the window, the player on the other side gets a point and
    the ball's position resets.  Draw each player's score in the
    window.
  






  
Challenge 3

  

    The game is kind of easy because the path of the ball is
    completely deterministic.  Make the game more interesting by
    speeding up the ball every time it bounces and give players the
    ability to add spin to the ball.  Players can spin the ball, or
    change its direction, by moving the paddle when it hits the ball.
    If the paddle is moving in the same direction as the ball, it will
    make the bounce angle more obtuse.  If the paddle is moving in the
    opposite direction as the ball, it will make the bounce angle more
    acute.  If the paddle is not moving, it should bounce like normal.
  




Submission


Please show your source code and run your programs for the instructor or lab assistant. Only a programs that have perfect style and flawless functionality will be accepted as complete.