How to overload operator << with linked list?

Question

For class, I am trying to overload the << operator so I can print out an object I created. I declared and added to this

WORD you; //this is a linked list that contains 'y' 'o' 'u'

and I want to do this

cout << you; //error: no operator "<<" matches theses operands

I have to overload the insertion operator as a friend function with chaining to print a word.

I have declared and defined the overloaded function, but it still does not work. Here is the class declaration file, followed by the .cpp file with the function

#include <iostream>

using namespace std;
#pragma once

class alpha_numeric //node
{
public:
char symbol; //data in node
alpha_numeric *next;//points to next node
};

class WORD
{
public:
WORD(); //front of list initially set to Null
//WORD(const WORD& other);
bool IsEmpty(); //done
int Length();
void Add(char); //done
void Print(); //dont
//void Insert(WORD bword, int position);
//WORD operator=(const string& other);

friend ostream & operator<<(ostream & out, alpha_numeric *front);//******************<-----------------

private:
alpha_numeric *front; //points to the front node of a list
int length;

};

In the .cpp file, I put *front in the parameter because it said front was not defined when I tried to use it inside the function, even though I declared it in the class. I then tried this. I have no clue if it is correct.

ostream & operator<<(ostream & out, alpha_numeric *front)
{
alpha_numeric *p;
for(p = front; p != 0; p = p -> next)
{
    out << p -> symbol << endl;
}
}

Why don't you create ostream& operator<<(ostream &out, WORD &word) ? — seva titov
– seva titov, Commented Jun 5, 2012 at 2:15
@SevaTitov It has to be implemented as a friend function, its in the homework directions — Mike
– Mike, Commented Jun 5, 2012 at 2:18

JsDoITao · Accepted Answer · 2012-06-05 02:25:26Z

1

If you want to overload << for class WORD, the parameter must be 'WORD' type. I think you must search overload for << 1stly before asking such question. :-)

class WORD
{
friend ostream & operator<<(ostream & out, const WORD& w);
}

ostream & operator<<(ostream & out, const WORD& w)
{
alpha_numeric *p;
for(p = w.front; p != 0; p = p -> next)
    out << p -> symbol;
out<<endl;
return out;
}

answered Jun 5, 2012 at 2:25

JsDoITao

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3 Comments

Mike Over a year ago

can you explain why it has to be const?

JsDoITao Over a year ago

@MikeGordon you do not want to make any change to WORD in operator<<, right? that's the reason.

behnaz.sheikhi Over a year ago

Thanks, @JsDoITao for your solution, I have other questions about this content. If the members such as symbol and next in-class alpha_numeric were private instead of public how we can handle them? I am new in C++ as well, and I have this issue but in class alpha_numeric symbol and next are private members and I gave the error of symbol and next are private in this content.

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