Question

For an assignment (and for myself) I need to be able to print a singlely linked list of “Stock” objects.

Each Stock as the following private data members:
1 int
1 string

This is my print function in the linked list class I had to use/develop. I am not allowed to use STL::list().

//list.h
template<class NODETYPE>
void List< NODETYPE>::print() const
{
if(isEmpty() ){
    cout<<"the list is empty\n\n";
    return;
}

ListNode< NODETYPE> *currentPtr=firstPtr;

cout<<"The list is: ";

while (currentPtr!=0){
    //cout << currentPtr->data << ' ';
    currentPtr = currentPtr->nextPtr;
}

cout<< "\n\n";
}

Now for the Nodes in the List, listnode.h:

//ListNode.h
//ListNode Template Definition
#ifndef LISTNODE_H
#define LISTNODE_H

template< class NODETYPE > class List;

template < class NODETYPE>
class ListNode {
friend class List < NODETYPE>;

public:
    ListNode (const NODETYPE &); //constructor
    NODETYPE getData() const;

private:
   NODETYPE data;
   ListNode< NODETYPE> *nextPtr;

};

 template<class NODETYPE>
 ListNode< NODETYPE >::ListNode(const NODETYPE &info): data (info), nextPtr(0)
 {

 }
 template<class NODETYPE>
 NODETYPE ListNode<NODETYPE>::getData() const{
    return data;
 }

#endif

Now my Stock Class:

class Stock{
public:
    Stock(); //default constructor
    Stock(string, int); //overloaded constructor
    ~Stock(); //deconstructor
    void setSymbol(string); //sets stock symbol
    void setShares(int);
    string getSymbol();
    int getShares();
private:
    string symbol;
    int shares;
};
Stock::Stock(){
symbol=" ";
shares=0;
}
Stock::Stock(string s, int num){
    cout<<"Creating Stock with supplied Values! \n\n"<<endl;
    symbol=s;
    shares=num;
    price=p;
}

Simple int main() for testing:

int main(){

List < Stock > portfolio_list;

Stock Google("GOOG", 500);
Stock VMware("VMW", 90);
Stock Apple("APL", 350);

portfolio_list.insertAtFront(Google);
portfolio_list.insertAtFront(VMware);
portfolio_list.insertAtFront(Apple);

portfolio_list.print();

return 0;

}

So obviously, I get operator errors for “<<” in list.h, because it can’t output the contents of my stock class. My end goal is to loop through every element in a linked list and print the string symbol and int. I’m assuming I will need to use some sort of operator overloading? Or am I way off base? If I do, should this be implemented in my Stock class? Thanks in advance.

Answer 1

If I understood your code, you’ll have to overload the << operator to both ListNode and List classes.

//Representation of ListNode
template <class T>
ostream& operator << (ostream& ostr, ListNode<T>& ls) {
    return ostr << "Foo"; //replace "Foo" with the proper representation
}

//Representation of List
template <class T>
ostream& operator << (ostream& ostr, List<T>& ls) {
    ostr << "[ ";
    for(ListNode<T> *i = ls.firstPtr; i != NULL; i = i->nextPtr)
        ostr << *i << " ";
    return ostr << "]";
}

Would print [ Foo Foo Foo ] for a 3 element list.

BTW, you should mark those functions as friend if you need to access private members.