unused variable in elevator.h

[zhaofeng-shu33]

There are some unused class private variables in elevator.h. For example, _items[i] for i > 0 (class Elevator); _item_num (class LinkedElevator?).

[Alpar Juttner]

The elements of _items are actually used through pointers. I agree it's a bit dirty. As far as I remember is it implemented this way for performance reasons.

On the other hand, _item_num is indeed unnecessary.

[zhaofeng-shu33]

I check the latest file elevator.h again. _items[0] is used but _items[i] are not used throughout the source code.

Can I make a patch to this file or contribute something equivalent?

[Alpar Juttner]

OK, I explain it in more details.

Syntactically, you could indeed replace std::vector<Item> _items with Item _item plus every instance of _items[0] with _item, and it would compile beautifully. But would crash immediately when trying to use it. Because the whole vector is indeed in heavy use through pointers.

In fact, it is a fundamental part of the data structure. It contains all items ordered by their levels and by their activeness. I.e. it starts with the active items on level 0, then come the inactive ones on level 0, then the active ones on level 1, then the inactive ones on level 1 etc. The vectors _first and _last_active indicate the borders of these intervals on each level. In addition, the map _where gives a cross reference to the elements. The values of these vectors are pointers (Item *), and the elements of _items are accessed and manipulated through them.

Right at the beginning, initStart() puts all items into _item. Later on, its values are manipulated with the functions copy() and swap().

I hope this helped.

[zhaofeng-shu33]

I understood now. Thank you very much.