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/* 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.
*/
#include <iostream>
#include <string>
using namespace std;
#include <deque>
#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
*/
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