Question

I have a class in which I m trying to overload the << operator. For some reason, it is not being overloaded.

Here is my .h file:

friend std::ostream& operator<<(std::ostream&, const course &); //course is my class object name

in my .cpp, I have this as my implementation:

std::ostream& operator<<(std::ostream &out, const course & rhs){
    out << rhs.info;
    return out;
}

This should be correct, but when I try to compile it, it says that cout << tmp; is not defined in ostream.

I ve included iostream in my .cpp and .h

I m been pulling my hair out trying to figure this out. Can you see anything that s wrong with this?

EDIT: Since what I m doing seems to be correct, here s all of my source code: http://pastebin.com/f5b523770

line 46 is my prototype

line 377 is the implementation

line 435 is where it fails when i attempt to compile it.

also, I just tried compiling it on another machine, and it gives this error instead:

course.cpp:246: error: non-member function  std::ostream& operator<<(std::ostream&, const course&)  cannot have cv-qualifier
make: *** [course.o] Error 1

Answer 1

The syntax you ve listed is correct, but the overloaded operator prototype has to be declared in the course definition to work properly.

course.h

class course {
public:
  friend std::ostream& operator<<(std::ostream&, const course&);
private:
  int info;
}

course.cpp

std::ostream& operator<<(std::ostream &out, const course &rhs){
  out << rhs.info;
  return out;
}

Answer 2

It looks fine to me. Here s my version of it:

course.h

#include <iostream>

class course
{
public:
    friend std::ostream& operator<<(std::ostream&, const course &); //course is my class object name
    int info;
    course(){info = 10;}
};

course.cpp

#include <iostream>    
#include "course.h"

std::ostream& operator<<(std::ostream &out, const course & rhs)
{
    out << rhs.info;
    return out;
}

main_file.cpp

#include <iostream>
#include "course.h"

int main()
{
    course a;
    std::cout<<a;

    return 0;
}

Answer 3

You should include the rest of the code, I don t think we can see where the problem is.

The following trivial example works:

class course
{
public:
    course(int info) : info(info) { }
    int info;

    friend std::ostream& operator<<(std::ostream&, const course &);
};

std::ostream& operator<<(std::ostream &out, const course & rhs)
{
    out << rhs.info;
    return out;
}

int main(int, char*[])
{
    course tmp(3);
    std::cout << tmp;
    return 0;
}

Answer 4

I found this helpful!

My insertion and extraction operators are slightly different.

here they are defined:

friend ostream& operator<<(ostream &fout, datatype toPrint)

friend istream& operator>>(istream &fin, datatype &toReadTo)

the syntax needs to be exact.

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