Hello All, First time here. I was hoping you could help me with my program. I'm trying to use the given Iterators to overload my = operator to print my list to screen. I keep getting Link2019 errer though and have narrowed the problem down to my print operator. I'm wondering if it has anything to do with the fact that my operator is in private part of class? I'm new to this concept.
Here is my header file, I'm not allowed to change it though.Code:#include "List.h" // methods for Node all //ME Node::Node( const string &s, Node * p, Node * z) : word( s ), next( p ), prev(z) //constructor { word = s; // init. word data with a copy of s next = p; // next pointer points to p prev = z; //prev pointer points to z } const string &Node::get_word( ) const // get a const reference to word { return word; //returns curent objects data } Node *Node::get_next( ) const // get a Node * (value of next) { return next; //returns current objects pointer to next } Node *Node::set_next( Node * p ) // set next to a new value { next = p; // next points to p return next; } Node *Node::get_prev( ) const // get a Node * (value of next) { return prev; //returns current objects pointer to next } Node *Node::set_prev( Node * z ) // get a Node * (value of next) { prev = z; return prev; //returns current objects pointer to next } //****************************************************************************8 // methods for List List::List( ) // constructor: init. head and tail { cout << "List::List( )\n"; head = tail = 0; } List::List( const List &rhs ) //Copy Constructor { copy_list( rhs ); } List::~List( ) // destructor: deallocate the list { cout << "List::~List( )\n"; delete_list( ); } void List::copy_list( const List &rhs ) //Given { head = tail = 0; // copy rhs' list into this for( Node *p = rhs.head; p; p = p->get_next( ) ) { push_back( p->get_word( ) ); } } void List::push_back( const string &s ) { // p points to a new node Node *p = new Node( s, 0, tail ); if( tail == 0 ) // tail not pointing to a node yet? { head = tail = p; // head & tail point to new node in the list } else { // tail->next points to new node tail->set_next( p ); tail = p; // tail points to last node in the list } } void List::pop_back( ) { if( tail ) // tail points to a node? { Node *tmp = tail; tail = tail->get_prev( ); delete tmp; // delete node to be removed if( tail == 0 ) // no more elements in the list? { head = 0; } else { tail->set_next( 0 ); } } } // other methods for List... void List::delete_list( ) //ME { for( Node *p = head; p; ) { Node *tmp = p; // remember current pointer p = p->get_next( ); // advance p to the next Node delete tmp; // deallocate tmp cout << "Deleted\t" << tmp << "\tnext is\t" << p << '\n'; } } void List::push_front( const string &s ) //ME { Node *p = new Node(s,0,head); if( head == 0 ) // head not pointing to a node yet? { head = tail = p; // head & tail point to new node in the list } else { // head->next points to new node p -> set_next(head); head = p; } } void List::pop_front( ) //ME { Node* temp; if(head == NULL) { cout<<"\nLinked list is empty"; return; } if(head->get_next() == NULL) //to check if only one node is present { temp = head; head = NULL; //cout<<"\nDeleted node: "<<temp->data; free(temp); } else //If more than one nodes are present { temp = head; head = head->get_next(); //cout<<"\nDeleted node: "<<temp->data; free(temp); } } List::Iterator List::begin( ) const // beginning of a linked list ME { return List::Iterator( head ); } List::Iterator List::end( ) const // end of a linked list ME { return List::Iterator( NULL ); } // methods for Iterator // constructor: init. an Iterator List::Iterator::Iterator( Node *p ) { current = p; } // get a const ref to word const string &List::Iterator::operator *( ) const { return current->get_word( ); } // get a const ref to word void List::Iterator::operator ++( ) { if( current ) { current = current->get_next( ); } } // current != p bool List::Iterator::operator !=( const Iterator &iter ) const { return current != iter.current; } List &List::operator =( const List &s ) { List::Iterator iter; for( iter = s.begin( ); iter != s.end( ); ++iter ) { cout << "List *iter = " << *iter << "\n"; } return (*this); }
And finally my main, something else I can't change. I commented everything out except cout statement.Code:#include <iostream> #include <iomanip> #include <string> using namespace std; class Node { public: Node( const string &, Node *, Node * ); const string &get_word( ) const;// get a const reference to word Node *get_next( ) const; // get a Node * (value of next) Node *set_next( Node * ); // set next to a new value Node *get_prev( ) const; // get a Node * (value of prev) Node *set_prev( Node * ); // set prev to a new value private: string word; Node *next; Node *prev; }; class List { public: List( ); // constructor List( const List & ); // copy constructor ~List( ); // destructor // push a node to the back of list void push_back( const string & ); // push a node to the front of list void push_front( const string & ); // pop a node from the back of list void pop_back( ); // pop a node from the front of list void pop_front( ); class Iterator { public: Iterator( Node * = 0 ); const string &operator *( ) const; void operator ++( ); bool operator !=( const Iterator & ) const; private: Node *current; }; Iterator begin( ) const; // pointer to beginning of the list Iterator end( ) const; // pointer to end of the list private: Node *head; Node *tail; void copy_list( const List & );// copy a linked list void delete_list( ); // delete a linked list // do NOT allow copy assign. operator List &operator =( const List & ); };
Code:#include "List.h" // implement operator <<( ) using Iterators ostream &operator <<( ostream &, const List & ); int main( ) { List la; // create list la la.push_front( "mom" ); la.push_back( "please" ); la.push_back( "send" ); la.push_back( "money" ); la.push_front( "hi" ); cout << "\nla contains:\n" << la << '\n'; /* List lb( la ); // copy list la to lb /* cout << "lb contains:\n" << lb << '\n'; lb.pop_front( ); lb.pop_front( ); lb.push_front( "mother" ); lb.push_front( "dear" ); lb.push_back( "Bubba" ); /* cout << "lb contains:\n" << lb << '\n'; /* List lc; // create list lc lc.push_back( "money" ); lc.push_front( "send" ); cout << "\nlc contains:\n" << lc << '\n'; List ld; // create list ld cout << "\nld contains nothing:\n" << ld << '\n'; ld.push_front( "hi" ); cout << "ld contains:\n" << ld << '\n'; ld.pop_front( ); cout << "ld contains nothing:\n" << ld << '\n'; ld.push_back( "hello" ); ld.push_back( "Bubba" ); cout << "ld contains:\n" << ld << '\n'; ld.pop_front( ); cout << "ld contains:\n" << ld << '\n'; ld.pop_front( ); cout << "ld contains nothing:\n" << ld << '\n'; List le( ld ); cout << "le contains nothing:\n" << le << '\n'; le.push_back( "last" ); cout << "le contains:\n" << le << '\n'; */ system("pause"); return 0; }
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