Lesson 8 · Implementing the Navigator Class — Knowledge ChecksAnswer key

How does the Navigator control the robot's motors?

1. A.It creates its own DifferentialDrive
2. B.It delegates to its LineTrack object, which controls the motors✓
3. C.It sets motor power directly
4. D.It doesn't move the robot at all

The Navigator asks LineTrack to turn and follow lines; LineTrack (built in Module 2) owns the DifferentialDrive. That's delegation — reusing code you already wrote.

Why does desired_heading() use self.position instead of a 'current' parameter?

1. A.To save memory
2. B.The Navigator object already knows its own position — that's the advantage of a class✓
3. C.Because parameters are not allowed in methods
4. D.It doesn't need the current position at all

A class bundles data with behavior. The Navigator stores its position, so its methods can read it directly instead of having it passed in every time.

Why drive straight(8) before track_until_cross() only when going straight ahead?

1. A.To speed the robot up
2. B.To clear the current intersection, so track_until_cross() finds the NEXT cross, not the one it's sitting on✓
3. C.To turn the robot around
4. D.To recharge the battery

When turning, turn_right() already moves off the cross. Going straight, the robot is parked on the cross — without clearing it, the sensors detect it immediately and stop early.

The path from Manhattan is [(1,0),(2,0),(2,1)]. How many times does drive_path call track_until_cross()?

1. A.Once
2. B.Three times — once per intersection in the path✓
3. C.Four times — including the start
4. D.It depends on the turns

drive_path loops once per element in the path, and each pass ends with a track_until_cross() to reach that intersection. Three elements → three calls. The start isn't in the path.