it compiles and runs, but in one moment it gives me an unhandled exception. I tracked the problem till i found it. it is the line in bold in my code. Whats wrong with it?

"LinkedList.h"

"Main.cpp"Code:#include <iostream> using namespace std; template<typename T> struct LinkedNode { T data; LinkedNode* next; LinkedNode* prev; }; template<typename T> class LinkedList { public: LinkedList(); ~LinkedList(); LinkedList(const LinkedList& rhs); LinkedList& operator=(const LinkedList& rhs); bool isEmpty(); LinkedNode<T>* getFirst(); LinkedNode<T>* getLast(); void insertFirst(T data); void insertLast(T data); bool insertAfter(T tKey, T tData); void removeFirst(); void removeLast(); bool remove(T removalCandidate); void destroy(); private: LinkedNode<T>* mFirst; LinkedNode<T>* mLast; }; template<typename T> LinkedList<T>::LinkedList() : mFirst(), mLast() { } template<typename T> LinkedList<T>::~LinkedList() { destroy(); } template<typename T> LinkedList<T>::LinkedList(const LinkedList &rhs) { destroy(); *this = rhs; } template<typename T> LinkedList<T>& LinkedList<T>::operator =(const LinkedList<T> &rhs) { if(this = &rhs) return *this; destroy(); mFirst = rhs.mFirst; mLast = rhs.mLast; return this*; } template<typename T> bool LinkedList<T>::isEmpty() { if(mFirst == 0) return true; else return false; } template<typename T> LinkedNode<T>* LinkedList<T>::getFirst() { return mFirst; } template<typename T> LinkedNode<T>* LinkedList<T>::getLast() { return mLast; } template<typename T> void LinkedList<T>::insertFirst(T tData) { LinkedNode<T>* newNode = new LinkedNode<T>(); newNode->data = tData; if(isEmpty()) mLast = newNode; else mFirst->prev = newNode; newNode->next = mFirst; mFirst = newNode; } template<typename T> void LinkedList<T>::insertLast(T tData) { LinkedNode<T>* newNode = new LinkedNode<T>(); newNode->data = tData; if(isEmpty()) mFirst = newNode; else mLast->next = newNode; newNode ->prev = mLast; newNode ->next = 0; mLast = newNode; } template<typename T> bool LinkedList<T>::insertAfter(T tKey, T tData) { if(isEmpty()) return false; LinkedNode<T>* current = mFirst; while(current->data != tKey) { current = current->next; if(current == 0) return false; } LinkedNode<T>* newNode = new LinkedNode<T>(); newNode->data = tData; if(current == mLast) { newNode->next = 0; mLast = newNode; } else { newNode->next = current->next; current->next->prev = newNode; } newNode->prev = current; current->next = newNode; return true; } template<typename T> void LinkedList<T>::removeFirst() { LinkedNode<T>* oldNode = mFirst; mFirst = mFirst->next; delete oldNode; oldNode = 0; } template<typename T> void LinkedList<T>::removeLast() { LinkedNode<T>* oldNode = mLast; delete oldNode; mLast = mLast->prev; } template<typename T> bool LinkedList<T>::remove(T removalCandidate) { if(isEmpty()) return false; LinkedNode<T>* current = mFirst;while(current->data != removalCandidate){ current = current->next; if(current == 0) return false; } if(current == mLast) { current->prev->next = 0; mLast = current->prev; } else { current->prev->next = current->next; current->next->prev = current->prev; } delete current; current = 0; return true; } template<typename T> void LinkedList<T>::destroy() { if(mFirst != 0) { LinkedNode<T>* current = mFirst; while(current != 0) { LinkedNode<T>* oldNode = current; current = current->next; delete oldNode; oldNode = 0; } } }

This code is supposed to simulate the std::list class.Code:#include "LinkedList.h" #include <iostream> #include <string> using namespace std; int main() { LinkedList<int> myIntList; // Insert to the front of the list. myIntList.insertFirst(4); myIntList.insertFirst(3); myIntList.insertFirst(2); myIntList.insertFirst(1); // Insert to the back of the list. myIntList.insertLast(5); myIntList.insertLast(7); myIntList.insertLast(8); myIntList.insertLast(9); // Forgot to add 6 to the list, insert before 7. But first // we must get an iterator that refers to the position // we want to insert 6. cout << "Before deletion..." << endl; myIntList.insertAfter(5, 6); // Print the list to the console window. for(LinkedNode<int>* i = myIntList.getFirst(); i != myIntList.getLast()->next; i = i->next) cout << i->data << " "; cout << endl; // Remove the first node in the list. myIntList.removeFirst(); // Remove the last node in the list. myIntList.removeLast(); // Remove the node that has a value of 5 myIntList.remove( 1 ); // Print the list to the console window. cout << "After deletion..." << endl; for(LinkedNode<int>* i = myIntList.getFirst(); i != myIntList.getLast()->next; i = i->next) cout << i->data << " "; cout << endl; system("PAUSE"); }