CS 40 Fall 2007 Homework 3

1. Make a world containing a helicopter and two light houses (Beach -> Lighthouse). Add a method circleAround that has a parameter of type Object named target. The method causes the helicopter to circle around the target. Use this strategy for circling:

• Make the helicopter face the target
• helicopter.move(helicopter.distance(target) - 10) toward target asSeenBy helicopter
• Make the helicopter turn 90 degrees
• In a loop, make the helicopter move a bit, turn a bit, move a bit, turn a bit, so that it eventually makes a complete circle. I did this by trial and error. Looping 100 times, turning 0.01 revolution each time, moving forward by 0.5 meters seemed to work for me. I put the turn and move in a "Do together", but I don't know if that is necessary. Of course, you could use math to figure out the values for turning and moving, but that would be un-American.

In World.my_first_method, first have the helicopter call circleAround(lighthouse), then have the helicopter call circleAround(lighthouse2).

20 points.

Grading criteria

a) Does the circleAround method have a parameter of type target?

b) Does the code of the circleAround method always refer to target, never to lighthouse?

c) Does the circling work?

d) Does my_first_method contain two calls to the circleAround method?

2. Make a class CirclingCopter, a helicopter with the circleAround method. (If you were unable to do part 1, just implement the method by having the helicopter say "I wish I could fly in a circle." You'll still get all points for this part.)

Your CirclingCopter should have some color or texture that makes it look different from the regular helicopter.

Make a world with two instances of that class. Have them both circle a single lighthouse (at different heights).

15 points

Grading criteria

a) Is there a class CirclingCopter in this world?

b) Are there two instances of the class in this world?

c) Does my_first_method contain two calls to the circleAround method?

Put two attachments, heli1.a2w and heli2.a2w into the eCampus assignment.