Logic issue with lists and loops in unityscript - for-loop

Question

I have 3 lists: ListOfBoxes, ListOfGoals and ListOfDoned.
these first 2 lists contain transforms, the 3rd is empty.
When a box from ListOfBoxes x and z position are the same as a goals in ListOfGoals i move that box to ListOfDoned.
What I want to happen next is; If a box in the ListOfDoned is no longer at a goal in ListOfGoals move back into ListOfBoxes.
Here Is My Code:
for(var n = 0; n < ListOfGoals.Count; n++)
{
for (var p = 0; p < ListOfBoxes.Count; p++)
{
if (Mathf.Abs(ListOfBoxes[p].position.x - ListOfGoals[n].position.x) < epsilon)
{
if (Mathf.Abs(ListOfBoxes[p].position.z - ListOfGoals[n].position.z) < epsilon)
{
Debug.Log("Box" + p + " has been placed at " + n);
ListOfDoned.Add(ListOfBoxes[p]);
ListOfBoxes.RemoveAt (p);
break;
}
}
}
}
for (var q = 0; q < ListOfDoned.Count; q++)
{
for (r = 0; r < ListOfGoals.Count; r++)
{
if (Mathf.Abs(ListOfDoned[q].position.x - ListOfGoals[r].position.x) < epsilon)
{
if (Mathf.Abs(ListOfDoned[q].position.z - ListOfGoals[r].position.z) < epsilon)
{
break;
}
else
{
if (r == ListOfGoals.Count)
{
ListOfBoxes.Add(ListOfDoned[q]);
ListOfDoned.RemoveAt (q);
}
}
}
}
}
I can see that what is happening is that it's checking all of the goals in the list instead of exiting if it has found one, but I'm not sure what the logic would be go get this working correctly.
Thanks in advance.
[EDIT to try to add clarity] - Imagine I have 2 boxes in ListOfBoxes and 2 goals in listofgoals. When 1 box moves to the same position as one of the goals (only x and z axis, not y) I want that box removed from ListOfBoxes to ListOfDoned. That's the first nested for loop, and it seems to be working fine. However if that box is later moved from the same position as one of those goals I need it back in ListOfBoxes. This is what I want the second nested for loop to do.
What appears to be happening is that it is comparing the boxes in listOfDoned with all of the goals in listofgoals and (even though it has the same position as one of the goals) it doesnt have the same position as the other one so the else case and put the box in the list listofboxes.
I need to check against the position of all the goals, and as long as it's position is the same as one of them, don't do anything, else return it to listOfBoxes.

Answer 1

[EDIT: This answer addresses what I believe is a problem in your code, but I don't think it fixes the behaviour you describe in your comments. Let me revise this pending more clarification.]
I believe the problem you describe is due to your if statement inside the second nested loop:
if (r == ListOfGoals.Count)
{
ListOfBoxes.Add(ListOfDoned[q]);
ListOfDoned.RemoveAt (q);
}
You need to remember that the contents of your loop will only execute if the condition you specified in your for loop is true. In this case, that is
r < ListOfGoals.Count
This means that your if condition r == ListOfGoals.Count can never occur, because the loop will terminate before r ever reaches up to ListOfGoals.Count. Since the condition never evaluates to true, items will never be moved from ListOfDoned to ListOfBoxes, even if they're supposed to be.
To fix this, I suggest changing your if statement to:
if (r == ListOfGoals.Count - 1)
{
ListOfBoxes.Add(ListOfDoned[q]);
ListOfDoned.RemoveAt (q);
}
Which would correspond to the last execution of the loop. Hope this helps! Let me know if you have any questions.

Answer 2

Thanks to PipsqueakGames on twitter for helping me reach this solution.
for(var n = 0; n < ListOfGoals.Count; n++)
{
for (var p = 0; p < ListOfBoxes.Count; p++)
{
if (Mathf.Abs(ListOfBoxes[p].position.x - ListOfGoals[n].position.x) < epsilon)
{
if (Mathf.Abs(ListOfBoxes[p].position.z - ListOfGoals[n].position.z) < epsilon)
{
Debug.Log("Box" + p + " has been placed at " + n);
ListOfDoned.Add(ListOfBoxes[p]);
ListOfBoxes.RemoveAt (p);
break;
}
}
}
}
for (q = 0; q < ListOfDoned.Count; q++)
{
var matched:boolean = false;
for (r = 0; r < ListOfGoals.Count; r++)
{
if (Mathf.Abs(ListOfDoned[q].position.x - ListOfGoals[r].position.x) < epsilon)
{
if (Mathf.Abs(ListOfDoned[q].position.z - ListOfGoals[r].position.z) < epsilon)
{
matched = true;
Debug.Log("Box" + q + " is still at " + r);
break;
}
}
}
if (!matched)
{
ListOfBoxes.Add(ListOfDoned[q]);
ListOfDoned.RemoveAt (q);
}
}