About the undo logic of skeleton code

[CurlyRhapsody]

While I was testing my PA2, I realized a problem that undoing a step that collected extra lives will increase the number of lives (instead of decreasing) by how many lives you have collected.

Here is an example:
I am at the left top position of the map. If I move down, I will collect 3 lives.

Then, I perform a down move and undo. Notice that the number of lives increased to 14 by moving down, and increased to 17 when performing undo.

I have checked the readme in PA1 again, and undo should be implemented as "decrease by the number of lives you collected in the previous move if any of them was collected".

Because of this, I started to think there might have a problem in the main logic of the project (i.e. The skeleton code).
I investigated it and then I found out there is actually a problem on line 82 of GameController.java (Inside the method processUndo()), which is written like this:

this.gameState.increaseNumLives(aliveState.collectedExtraLives.size());

This line should have used decreaseNumLives instead of increaseNumLives. However, I attempted to fix this problem and found out that either changing the function into decreaseNumLives or multiplying the parameter by -1 will fail the sanity test.

Because of this, I would like to ask whether if this is normal or it is actually a problem that needs to be fixed. Thanks!

[henryhchchc]

There is no need to care about the behavior of the GameController since it is part of the logic in PA1. Just follow the logic of the provided skeleton code and focus on implementing the GUI.

[enor2017]

So it is just the game design and we don't need to fix it, or the GameController is fine but we need to fix this problem in our GUI implementation?

Or, why should it be increaseNumLives rather than decreaseNumLives? I read through the logic but cannot understand this.

[henryhchchc]

This is a bug in the reference implementation of PA1. In PA2 we are not putting our main focus on game logic. You don't need to care about the internal logic of GameController, simply calling its methods are fine. We won't deduct any point because of a bug in the game logic.

[enor2017]

OK, thank you so much for the clarification.