Programming and Design with Alice - Assignment Example

The following is the design process.

            The first design using pseudocode is very simple: step up and step down so that the mouse and cat legs move up and down. This does not work because we have not yet defined the movement.

Front right leg up

Front left leg down

Back left leg up

Back right leg down

            Alice does not have primitive methods to perform the front left leg up and the front left leg down. It is therefore required that the code for this movement be designed. Elegant design requires that methods are kept from being too large. To maintain a small size for the methods, additional methods are added to do the small tasks. The following is done

Call the frontRightLegUp function

Do together

Call the frontLeftLegUp function

Call the frontRightLegDown function

            Now the next step is to order this movement

Do together

Front left leg up

Front right leg down

Do together

Back left leg up

Back right leg down

The final storyboard is as follows

Do together

A cat sits on the floor.

The mouse sits beside the cat

Do in order

The cat turns around and notices the mouse

The mouse looks back at the cat

The mouse takes one step ahead of the cat

The cat follows the cat

The mouse always makes one step ahead of the cat

            A loop is implemented at the point where the mouse takes a step ahead of the mouse. This loop ensures that whenever the mouse takes a step the cat takes another step of the same magnitude so that the mouse is always one step ahead of the cat.

            The next step is transforming the storyboard into program code. The first action of the storyboard is the mouse turns to see the cat. The first method, therefore, turns to face. We use the turn-to-face to make the mouse turn to look in the direction of the cat. The next step is the cat taking one step away from the cat. We use the move-away method.

            Alice contains control statements that are vital in controlling movements. In the cat chase program, the cat moves away from the cat while the cat moves towards the mouse. The control statement Do in order is used to tell Alice to first make the cat look at the mouse and the mouse move away from the cat.   

            Other actions must be done together.  When the front right leg is up, for example, the front left leg must be held down. To achieve this functionality Alice is told to Do these actions together through the DO together control statement.

           To implement this program into Alice a scene must first be created. The initial scene is a room (Farooq, 2012). The intention of the cat is to catch the mouse. It should follow it while the mouse should always be one step ahead of the cat. We select the room scene and then a cat and a mouse.

           The next stage is in the program code editor. The code that makes the program is written. In Alice, the program code editor is at the bottom right of the main window. The instructions are edited in the area labeled World. my first method which can be renamed to anything of the programmer’s liking. Since the cat chase program is so simple it can be programmed in just one method. The first pair of the code is inserted in the Do in order block. In the cat’s methods, there is a turn-to-face method that is selected and dragged to the Do in order block. This method requires an argument i.e. the object that the cat should turn to face. The mouse is then picked as the object to be faced. The next method is to move away from where the mouse moves away from the cat. Lastly, the cat moves towards the mouse. 

The program is executed by pressing the play button.