public void Undo(UndoStack stack)
 {
     for (int i = 0; i < undolist.Length; ++i)
     {
         stack.RunUndo(undolist[i]);
     }
 }
 public void Undo(UndoStack stack)
 {
     for (int i = 0; i < undolist.Length; ++i)
     {
         stack.RunUndo(undolist[i]);
     }
 }