Week 11 Lab: Better Scribbler Movement

For this lab, you are going to write code to make your Scribbler robot be able to go to certain locations on the whiteboard, using some classes.

Step 1: Make the lab11 folder, etc.

Open Eclipse and make sure you are in the workspace S:\workspace. Make a lab11 folder. Then ***copy*** the move.py file over from your lab7 folder into your lab11 folder. (move.py should be unchanged from lab7.)

Make a new file called scribpoint.py. Put this new class definition into it:

class ScribPoint:
    def __init__(self):
        self.x = 0
        self.y = 0

This class will represent an (x, y) coordinate on a whiteboard on the floor where the Scribbler is, or will go to. Initially, the point being represented is (0, 0).

Step 2: Adding getter and setter methods

Now, add the getter and setter methods for x and y. Call them, getX(), getY(), setX(), and setY().

Step 3: Import scribpoint into move.py

Open the move.py file. At this point, I recommend that you only have one move.py file open in Eclipse. If you have two of them open (one from lab11) you might edit the wrong one.

Now, in move.py, at the top by the other imports, put this:

from scribpoint import *

Step 4: New function goToPoint()

In move.py, we are going to add a new function, goToPoint(), to make a Scribbler robot go to a point on the x,y coordinate plane.

• Near the bottom of move.py, after the last function, create a new function definition called goToPoint():

• Let’s assume that the x,y coordinate system has the standard orientation as in math class: with x being the horizontal axis, increasing to the right, and y being the vertical axis, increasing upward.  Also, we assume that whereever you put the scribbler down on the whiteboard, it is at (0, 0) and facing the positive x axis. (i.e., facing "east")
• You need to use the atan2() function from the math package.  Look up atan2() in the math package on Google now. Notice the order of the arguments!
• You’ll also need to use math's degrees() function to convert radians to degrees, because our current API uses degrees. (To use math you'll have to import it... hint, hint...)
• Your goToPoint() function should leave the scribbler facing in the correct orientation -- i.e., "looking" at the positive X axis.  That way if you call goToPoint() multiple times in a row, you can always assume it is oriented correctly.
• Write the code now for goToPoint(start, end). Your code should:
  • Calculate deltaX and deltaY, based on start's and end's x and y values. (Recall, start and end are ScribPoint objects.) Hint: You get the x value from start by calling start.getX().
  • Call atan2(deltaY, deltaX) and then convert the results to degrees, and store in a variable angle.
  • Compute the distance to the new point (which is (deltaX, deltaY) relative to where the Scribbler is now).
  • Make the Scribbler move to the new point, using turnDegrees() and travelForw().
  • Make the Scribbler turn back to face east.

Step 5: Add code to test goToPoint()

Now, create a file lab11.py. At the top of that, add the magic code to import __future__ stuff. Then, add the line to import move, like we've been doing.

Add code to lab11.py to:

• connect to a scribbler
• create a ScribPoint object (which by default initializes it to location (0, 0)).
• create a second ScribPoint object. After creation, set its x and y attributes to 16 and 12, respectively. Thus, the object will represent point (16, 12) on the whiteboard.
• Use goToPoint() to make the Scribbler move to location (16, 12) -- i.e. the location represented by this second ScriptPoint object. Remember, that you have to pass in two ScribPoint objects to the function: the first is where the Scribbler is (i.e., (0, 0)), and the 2nd is where you want the Scribbler to go to.
• Use goToPoint() to make the Scribbler move back to (0, 0).

Put a marker in your Scribbler and run your code. See if your line segment is close to the 20 cm. It should be.

Create more ScribPoint() objects and to test your goToPoint() to make sure it really works.

Step 6: Draw a 5 point Star

***Replace*** the code you have in lab11.py with code to draw a 5-pt star with these points

• 5, 20
• 45, 20
• 12.5, 45
• 25, 5
• 37.5, 45

Remember that where ever you put the Scribbler down is point (0, 0), and whichever direction you have it facing is the +x axis. Also, you don't really want to draw a line from (0, 0) to (5, 20). So, you'll have to make some adjustments to get this to work.

Step 5: Submit your code

Clean up any code in lab11.py that isn't relevant anymore (old print statements, etc.) Make sure your code is well-documented, indented, hospitable, etc. Make sure you have the correct information in it about you, the author.

To submit your final version of lab11.py and move.py, you’ll need to use Windows Explorer.

• Open the Windows Explorer (shortcut: WindowsKey - e)
• Find your lab11.py, scribpoint.py, and move.py files down in your lab11 folder.
• Copy lab11.py, scribpoint.py, and move.py.
• Now, navigate to T:\CS104\current\<yourid>\.
• Create a folder there called lab11. (Do NOT call it Lab11 or lab 11 or Lab 11 or VivaLaFrance. Call it lab11.)
• Look again at the folder you just created. Is it called lab11? If not, do something silly, and then rename the folder lab11.
• Paste all the files (lab11.py, scribpoint.py and move.py) into that folder.

Grading Rubric: 15 points total

10 points: program that runs correctly.  There are many parts to handle in this program, so make sure all work correctly.
1 points: correct comments at the top of the file.
4 points: code is clean and neat and uses good comments and variable names. I.e., the code is hospitable.