CS 1101: Lab 2 - Part 1

Extending the Soccer Animation from Lab 1

Now that we have learned about structs, we can create a single game with both the ball and the goalie. The information that defines each frame in the animation now has two pieces: the x-coordinate of the ball and the y-coordinate of the goalie. We need to create a struct to hold these values, and we need to extend the functions for drawing, moving, and reacting to inputs so that the functions consume and return a struct instead of consuming and returning a single coordinate.

You may copy any code you need from your Lab 1 file as you work on these exercises. Name your file lab2.

  1. Write a data definition and examples of data for a struct for a game, which has both a ball and a goalie. (Your struct needs to represent the x-coordinate of the ball and the y-coordinate of the goalie.)

  2. Write a function draw-game that consumes a game struct and produces a scene containing both a ball and a goalie. Reuse your old functions from Lab 1 wherever possible.

  3. Write a function update-game that consumes a game struct and produces a new game struct. In the returned game, the position of the ball should change using your old update-ball-x function, and the goalie should be unchanged. Write test cases for your function.

  4. Write a function react-game that consumes a game struct and a string (representing a key press) and produces a game struct. In the returned game, the ball should be unchanged and the goalie should change using your old goalie-react function. Write test cases for your function.

  5. Put it all together using the following commands, substituting a starting value for an-initial-game-structure (your starting value should be a struct): 

          (big-bang an-initial-game-structure
                (on-tick update-game)
                (to-draw draw-game)
                (on-key react-game))
    You should now get the combined effects of the ball and goalie in a single game. In future assignments, we'll learn how to write more sophisticated animations where the different elements of the "world" interact.
Use turnin to turn in your animation. Proceed to part 2 of the lab by choosing one of the options on programming with structs.