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/*
* This file contains code from "C++ Primer, Fourth Edition", by Stanley B.
* Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the
* copyright and warranty notices given in that book:
*
* "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo."
*
*
* "The authors and publisher have taken care in the preparation of this book,
* but make no expressed or implied warranty of any kind and assume no
* responsibility for errors or omissions. No liability is assumed for
* incidental or consequential damages in connection with or arising out of the
* use of the information or programs contained herein."
*
* Permission is granted for this code to be used for educational purposes in
* association with the book, given proper citation if and when posted or
* reproduced.Any commercial use of this code requires the explicit written
* permission of the publisher, Addison-Wesley Professional, a division of
* Pearson Education, Inc. Send your request for permission, stating clearly
* what code you would like to use, and in what specific way, to the following
* address:
*
* Pearson Education, Inc.
* Rights and Contracts Department
* 75 Arlington Street, Suite 300
* Boston, MA 02216
* Fax: (617) 848-7047
*/
template <class Type> class Queue {
// interface functions to Queue are unchanged
public:
Queue(): head(0), tail(0) { }
// copy control to manage pointers to QueueItems in the Queue
Queue(const Queue &Q): head(0), tail(0) {copy_elems(Q);}
Queue& operator=(const Queue&);
~Queue() { destroy(); }
// return element from head of Queue
// unchecked operation: front on an empty Queue is undefined
Type& front() { return head->item; }
const Type front() const { return head->item; }
void push(const Type &);// add element to back of Queue
void pop(); // remove element from head of Queue
bool empty() const { // true if no elements in the Queue
return head == 0;
}
private:
// workaround: MS Compiler doesn't allow nested template class
// to be defined outside the class body
//struct QueueItem; // forward declaration of nested type QueueItem
struct QueueItem {
QueueItem(const Type &t): item(t), next(0) { }
Type item; // value stored in this element
QueueItem *next; // pointer to next element in the Queue
// MS won't allow definition outside the class so no static members
// of nested template classes
//static int static_mem;
};
QueueItem *head; // pointer to first element in Queue
QueueItem *tail; // pointer to last element in Queue
// utility functions used by copy constructor, assignment and destructor
void destroy(); // delete all the elements
void copy_elems(const Queue&); // copy all elements from parameter
private:
// copy all elements from input range denoted by iterator pair
// workaround: MS Compiler requires member templates to be
// defined inside the class body
template <class Iter> void copy_elems(Iter, Iter)
{
while (beg != end) {
push(*beg);
++beg;
}
}
};
template <class Type>
void
Queue<Type>::copy_elems(const Queue &orig)
{
// copy elements from orig into this Queue
QueueItem *pt = orig.head;
while (pt) { // last element has next pointer == 0
push(pt->item); // copy the element
pt = pt->next; // get the next one from orig
}
}
template <class Type>
Queue<Type>& Queue<Type>::operator=(const Queue &rhs)
{
if (this != &rhs) {
// destroy elements on this Queue
destroy();
copy_elems(rhs); // copy from rhs into left-hand Queue
}
return *this;
}
template <class Type>
void
Queue<Type>::destroy()
{
while (!empty())
pop();
}
template <class Type>
void Queue<Type>::push(const Type &val)
{
// allocate a new QueueItem object
QueueItem *pt = new QueueItem(val);
// put item onto existing queue
if (empty())
head = tail = pt; // queue has only one element
else
{
tail->next = pt; // add new element to end of queue
tail = pt;
}
}
template <class Type>
void Queue<Type>::pop()
{
// pop is unchecked: popping off an empty Queue is undefined
QueueItem* p = head; // keep pointer to head so can delete it
head = head->next; // head now points to next element
delete p; // delete old head element
}
/* workaround: MS Complier doesn't allow member templates to be
* defined outside the class body
template <class Type> template <class Iter>
void Queue<Type>::copy_elems(Iter beg, Iter end)
{
while (beg != end) {
push(*beg);
++beg;
}
}
* because can't define a member oustide the class, also can't
* have static members of nested template classes
// defines an int static member of QueueItem,
// which is a type nested inside Queue<Type>
template <class Type>
int Queue<Type>::QueueItem::static_mem = 1024;
*/
#include <iostream>
using std::cout; using std::endl;
Queue<int> queue1;
int main()
{
for (int ix = 0; ix != 1024; ++ix)
queue1.push(ix);
for (int ix = 0; ix != 1024; ++ix) {
int i = queue1.front(); // check next item
if (i != ix)
cout << "Something's wrong! i = " << i
<< " ix = " << ix << endl;
queue1.pop(); // and remove it
}
if (!queue1.empty())
cout << "Queue is not empty but should be!" << endl;
else
cout << "OK, queue empty again" << endl;
for (int ix = 0; ix != 1024; ++ix)
queue1.push(ix);
Queue<int> queue2(queue1); // use copy constructor
for (int ix = 0; ix != 1024; ++ix) {
int i = queue2.front(); // check next item
if (i != ix)
cout << "Something's wrong! i = " << i
<< " ix = " << ix << endl;
queue2.pop(); // and remove it
}
if (!queue2.empty())
cout << "queue2 is not empty but should be!" << endl;
else
cout << "OK, queue2 empty again" << endl;
queue2 = queue1; // use asssignment operator
for (int ix = 0; ix != 1024; ++ix) {
int i = queue2.front();
if (i != ix)
cout << "Something's wrong! i = " << i
<< " ix = " << ix << endl;
queue2.pop();
}
if (!queue2.empty())
cout << "queue2 is not empty but should be!" << endl;
else
cout << "OK, queue2 empty again" << endl;
}