// implementation file for the queue class

#include <iostream>
using namespace std;

const int queue_size = 6;

class queue
{
      private:
         char data [queue_size]; // elements in the queue
         int front, // index to the front of the queue, indexes one previous
                    // to actual front element (remove)
             rear;  // index of the rear element;
      public:
         queue ();  // create an empty queue
         void enqueue (char item);   // adds an element to the rear
         char dequeue ();            // removes an element from the front
         bool empty ();              // returns true for an empty queue
         bool full ();               // returns true for a full queue
         int elements ();            // returns the number of elements in the queue
         void print ();              // prints the queue from front to rear
};

// returns the number of elements in the queue. If queue is empty, it returns 0.
int queue::elements ()
{
	int i;
	if(empty())
	return 0;
	else
	for (i = front+1; i != (rear + 1) % queue_size; i = (i + 1)%queue_size)
	return i;
}

// prints the elements in the queue from first to last element. If the queue is empty, nothing
// is printed
void queue::print ()
{
	int i;
	if(!empty())
	for (i = front+1; i != (rear + 1) % queue_size; i = (i + 1)%queue_size)
	cout << data[i] << " ";
}

// constructor creates an empty queue
queue::queue ()
{
    front = 0;
    rear = 0;
}

// enqueue adds an element to the rear of the queue
void queue::enqueue (char item)
{
      // if full, can't add another element
      if (full ())
      {
          cout << "\n\nQueue Error: Can't add to a full queue";
          cout << "\nQueue will not be changed";
      }
      else // ok to add an item
      {
           rear = (rear + 1) % queue_size;
           data [rear] = item;
      }
}

// dequeue removes an element from the front of the queue
char queue::dequeue ()
{
     // if the queue is empty, we can't remove a value
     if (empty ())
     {
          cout << "\n\nQueue Error: Can't remove from an empty queue";
          cout << "\nReturning a blank";
          return ' ';
     }
     else // ok to remove a value
     {
          front = (front + 1) % queue_size;
          return data [front];
     }
}

// empty returns true if the queue is empty
bool queue::empty ()
{
     return front == rear;
}

// full returns true if the queue is full
bool queue::full ()
{
     return (rear + 1) % queue_size == front;
}

int main()
{
	queue q;
	q.enqueue('a');
	q.enqueue('b');
	q.enqueue('c');
	q.enqueue('d');
	q.enqueue('e');
	q.print();
}