In C++, I want to implement a ring iterator for a deque that contains a personally defined class.

Question

I have a function of a "Table" class that should add a player to the table. I decided that if the seat is taken, the function should try and go through all the seats and add the player to the next available seat. How do I implement this in my addPlayer function?

int Table::addPlayer(Player player, int position)
{
deque<Player>::iterator it;

if(playerList[position] != "(empty seat)") {
    //What goes here?
}
playerList.put(player,it);
cout >> "Player " >> player.toString >> " sits at position " >> position >> endl;

}

Answer 1

Instead of using position, use the iterator to point to that position, using something like this:

it = playerList.begin() + position;

Then, check if the seat is taken using the iterator. If the seat is taken, increment the iterator, but check for end, like this:

while (no empty seat found yet)
   {
   ++it;
   if (it==playerList.end()) it = playerList.begin();
   }

Of course, if all seats have been taken, this will result in an endless loop. Therefore, also keep the iterator you started from (let's call this itStart), and add a check on it:

while (no empty seat found yet)
   {
   ++it;
   if (it==playerList.end()) it = playerList.begin();
   if (it==itStart) break;       // We tried all seats
   }

Answer 2

Maybe you should also take a look at the circular buffer from boost.

http://www.boost.org/doc/libs/1_43_0/libs/circular_buffer/doc/circular_buffer.html

I think it will do what you want, and is quite easy to use.