My ostream and istream friend function can't access private class members

Question

My code:

matrix.h

#include <iostream>

class Matrix {
private:
    int row;
    int col;
    int **array;

public:
    Matrix();
    friend std::ostream& operator<<(ostream& output, const Matrix& m);
};

matrix.cpp

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

Matrix::Matrix()
{
    row = 3;
    col = 4;

    array = new int*[row];

    for (int i = 0; i < row; ++i)
    {
        array[i] = new int[col];
    }

    for (int i = 0; i < row; ++i)
    {
        for (int j = 0; j < col; ++j)
        {
            array[i][j] = 0;
        }
    }
}

std::ostream& operator<<(std::ostream& output, const Matrix& m)
{
    output << "\nDisplay elements of Matrix: " << std::endl;

    for (int i = 0; i < m.row; ++i)
    {
        for (int j = 0; j < m.col; ++j)
        {
            output << m.array[i][j] << " ";
        }
        output << std::endl;
    }

    return output;
}

main.cpp

#include "matrix.h"
#include <iostream>
using namespace std;

int main()
{
    Matrix a;
    cout << "Matrix a: " << a << endl;

    system("pause");
    return 0;
}

Error:

member "Matrix::row" (declared at line 3 matrix.h") is inaccessible
member "Matrix::col" (declared at line 3 matrix.h") is inaccessible
member "Matrix::array" (declared at line 3 matrix.h") is inaccessible
binary '<<' : no operator found which takes a right-hand operand of type 'Matrix'
'ostream': ambiguous symbol
'istream': ambiguous symbol

What am I doing wrong? :(

**Edited: I've editted the question to give a MCVE example like Barry suggested, and also removed using namespace std like Slava recommended. I'm still getting the same error.

Please provide a [minimal, **complete**, and verifiable example](http://www.stackoverflow.com/help/mcve). Is `Matrix` is a namespace? — Barry, Sep 25 '15 at 15:18
What I posted is my exact code. The only part I left out is other functions by using "..." @Barry — ChewingSomething, Sep 25 '15 at 15:21
Your Matrix class doesn't include ``? Or have a closing `};`? — Barry, Sep 25 '15 at 15:23
Oh it does have }; but no it does not include . Is that the problem why it doesn't work? @Barry — ChewingSomething, Sep 25 '15 at 15:24
I've added #include but the errors are still the same. @Barry — ChewingSomething, Sep 25 '15 at 15:26
Please review the MCVE link and post a complete example. Without a complete and verifiable example, it's impossible to know what the problem is. — Barry, Sep 25 '15 at 15:28
Check what ostream and istream classes you reference in the header file. It looks like there are 2 different classes for each name available. — Simon Kraemer, Sep 25 '15 at 15:31
@Barry okay, I've edited the question again. I hope I'm doing it right cz I'm new here. — ChewingSomething, Sep 25 '15 at 15:56
@SimonKraemer This is the new complete code of my program. Trying to provide a minimal code for people to ease you guys in detecting where my problem is. — ChewingSomething, Sep 25 '15 at 15:56

score 2 · Accepted Answer · answered Sep 25 '15 at 16:03

Now that you have a complete example, you're missing std:: here:

friend std::ostream& operator<<(ostream& output, const Matrix& m);
                              ^^^

Add it and everything compiles fine:

friend std::ostream& operator<<(std::ostream& output, const Matrix& m);

score 1 · Answer 2 · answered Sep 25 '15 at 15:33

1

What am I doing wrong? :(

It is a bad practice to put statement using namespace std; into header, and there is a reason for that. According to this:

'ostream': ambiguous symbol 'istream': ambiguous symbol

You have istream and ostream declared in global namespace somewhere. Follow good practice, it is not so difficult to type std::

answered Sep 25 '15 at 15:33

Slava

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Okay, here's the new edited code.. I've followed your suggestion. Not sure if I'm doing it right though cz I'm new to c++ and I've always used using namespace std in all my programs.. I can still use using namespace std in my Main.cpp right? – ChewingSomething Sep 25 '15 at 15:58
1

@ChewingSomething show exact errors, not your interpretations – Slava Sep 25 '15 at 16:02

My ostream and istream friend function can't access private class members

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