C++/Queue Stack/your queue

Create your own queue based on deque

<source lang="cpp">

/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/

1. include <iostream>
2. include <string>

using namespace std;

1. include <deque>
2. include <exception>

template <class T> class Queue {

 protected:
   std::deque<T> c;        // container for the elements
 public:
   /* exception class for pop() and top() with empty queue
    */
   class ReadEmptyQueue : public std::exception {
     public:
       virtual const char* what() const throw() {
           return "read empty queue";
       }
   };
 
   // number of elements
   typename std::deque<T>::size_type size() const {
       return c.size();
   }
   // is queue empty?
   bool empty() const {
       return c.empty();
   }
   // insert element into the queue
   void push (const T& elem) {
       c.push_back(elem);
   }
   // read element from the queue and return its value
   T pop () {
       if (c.empty()) {
           throw ReadEmptyQueue();
       }
       T elem(c.front());
       c.pop_front();
       return elem;
   }
   // return value of next element
   T& front () {
       if (c.empty()) {
           throw ReadEmptyQueue();
       }
       return c.front();
   }

};

int main() {

  try {    
     Queue<string> q;
     // insert three elements into the queue
     q.push("These ");
     q.push("are ");
     q.push("more than ");
     // read and print two elements from the queue
     cout << q.pop();
     cout << q.pop();
     // push two new elements
     q.push("four ");
     q.push("words!");
     // skip one element
     q.pop();
     // read and print two elements from the queue
     cout << q.pop();
     cout << q.pop() << endl;
     // print number of remaining elements
     cout << "number of elements in the queue: " << q.size()
          << endl;
     // read and print one element
     cout << q.pop() << endl;
  }
  catch (const exception& e) {
     cerr << "EXCEPTION: " << e.what() << endl;
  }

} /* These are four words! number of elements in the queue: 0 EXCEPTION: read empty queue

*/        
 </source>