template <class T>
class AQueue {

   private:
        T *ring;
        int capacity, count, head, tail;

   public: 
        // creates an empty queue of the given size.
        // quits if the capacity is unreasonable.
        AQueue (int capacity);

        // enqueues the item at the end of the queue.
        // quits if no space for item.
        void enqueue (T item);   

        // dequeues and returns the item from the front of the queue.
        // quits if queue is empty.
        T dequeue ();   

        // returns number of items in queue
        int size () const;   

        // returns the item from the front of the queue, without changing the queue.
        //quits if queue is empty.
        T look () const; 
};

// creates an empty queue of the given size.
// quits if the capacity is unreasonable.
template <class T>
AQueue<T>::AQueue (int capacity) {
     count = head = tail = 0;
     if (capacity < 1 ) {  // initialize fields and quit
          capacity = 1; 
          ring = new T[1];
          quit("AQueue<T>::AQueue - capacity too small\n");
     }
     ring = new T [capacity];
     this -> capacity = capacity;
} 

// enqueues the item at the end of the queue.
// quits if no space for item.
template <class T>
void AQueue<T>::enqueue (T item) {
     if (count == capacity) 
          quit("AQueue<T>::enqueue - queue full\n");

     ring[tail] = item; count++;
     tail = (tail + 1) % capacity;
}

// dequeues and returns the item from the front of the queue.
// quits if queue is empty.
template <class T>
T AQueue<T>::dequeue () {
     T result;
     if (count == 0) 
          quit("AQueue<T>::dequeue - queue empty\n");

     result = ring[head];
     count--;
     head = (head + 1) % capacity;
     return result;
}

// returns number of items in queue
template <class T>
int AQueue<T>::size () const {
     return count;
}

// returns the item from the front of the queue, without changing the queue.
// quits if queue is empty.
template <class T>
T AQueue<T>::look () const {
     if (count == 0) 
          quit("AQueue<T>::look - queue empty\n");

     return ring[head];
}