/// <summary>
/// Creates an ordered waiter.
/// </summary>
/// <param name="startPos">If startPos is >= 0 then waiter starts from that position.
/// If not something will need to hit increment |startPos| times.</param>
public OrderedWaiter(long startPos)
{
_waiters = new Heap <WaitStats>((s1, s2) => s1.Line > s2.Line);
_currCleared = startPos;
}
/// <summary>
/// Creates an ordered waiter.
/// </summary>
/// <param name="firstCleared">If true, then the first position (that is,
/// position 0) will be considered already free to proceed. If not something
/// will need to hit increment.</param>
public OrderedWaiter(bool firstCleared = true)
{
_waiters = new Heap <WaitStats>((s1, s2) => s1.Line > s2.Line);
_currCleared = firstCleared ? 0 : -1;
}