Please really need help with overloading operators!

[slomotion]

Thank you

[kbw]

You have to work backwards. Look at it like this.

I'd expect to write code like:

Frac a(3, 9);
Frac b(10, 6);
Frac c = a + b;

And that implies that it's declared like:

Frac operator+(const Frac& a, const Frac& b);

Using your existing interface, it'd be implemented as:

Frac operator+(const Frac& a, const Frac& b)
{
    Frac result;
    result.add(a, b);
    return result;
}

[Catfish666]

And also overload the pre-increment and post-increment operators ++ which will add 1 to the value of the fraction.

These are a bit tricky, so I'll help.

class Frac
{
public:

    // pre-increment
    // return a reference to *this
    Frac & operator ++ ();

    // post-increment (note int dummy parameter)
    // return a copy of Frac before updating
    Frac operator ++ (int);

    // operator== and operator!= are best implemented externally to Frac
    // this is so that the first parameter doesn't need to be Frac

    friend bool operator == (const Frac &, const Frac &);
    friend bool operator != (const Frac &, const Frac &);
};

Frac & Frac::operator ++ ()
{
    num += den; // just like Frac::addone()
    return *this;
}

Frac Frac::operator ++ (int)
{
    Frac temp(*this); // make a copy of current Frac

    num += den;
    return temp;
}

// operator== and operator!= are best implemented externally to Frac
// this is so that the first parameter doesn't need to be Frac if you
// want to compare a Frac to another type

bool operator == (const Frac &lhs, const Frac &rhs)
{
    // lhs - left hand side
    // rhs - right hand side

    if (lhs.num == rhs.num)
        return lhs.den == rhs.den;

    return false;
}

Edit: relevant link: http://www.parashift.com/c++-faq-lite/increment-pre-post-overloading.html

[slomotion]

Thank you

[Catfish666]

@Catfish666 could you please help me with the first portion as well? That is the one I don't understand at all.

What exactly? How to overload the >> << + - * / == != operators?

[slomotion]

Thank you

[Catfish666]

Well kbw already showed you how to overload operator+.
Operators - * / are overloaded the same way as +, you only need to change the operation accordingly: subtraction, multiplication, division.

Then I showed you post- and pre- increment, and equality and inequality operators.

So what's left is only the >> and << operators.

They are used to input and output your Frac. See these links:
http://www.parashift.com/c++-faq/input-operator.html
http://www.parashift.com/c++-faq/output-operator.html

[slomotion]

Thank you

[Catfish666]

#include <iostream>
#include <istream>
#include <ostream>

class Frac
{

friend std::ostream & operator << (std::ostream &, const Frac &);
friend std::istream & operator >> (std::istream &, Frac &);

};

std::ostream & operator << (std::ostream &os, const Frac &f)
{
    os << "Fraction is: " << f.num << '/' << f.den << std::endl;
    return os;
}

std::istream & operator >> (std::istream &is, Frac &f)
{
    // printing shouldn't happen here, just reading!
    // so this is just an example.
    std::clog << "Function reading!\n";
    std::clog << "Enter num: ";
    is >> f.num;
    std::clog << "Enter den: ";
    is >> f.den;
    return is;
}

int main()
{
    Frac f;

    // now these should work
    std::cin >> f;
    std::cout << f;
}

[slomotion]

Thank you

[Catfish666]

But could I have just done only for the top part and would it still work out the same?

I don't understand your question.

Do you mean using namespace std; so that you can remove the std:: prefixes?
That is a bad habit that you should unlearn.

http://www.parashift.com/c++-faq/using-namespace-std.html

And as for the - operator, is this correct? And that's all I need to do, correct?

It looks correct to me, yes.