Operators Overload

#include <iostream>

struct Rational {
    Rational(int numerator = 0, int denominator = 1) : numerator_(numerator), denominator_(denominator) {};

    void add(Rational rational) {
        numerator_ = numerator_ * rational.denominator_ + rational.numerator_ * denominator_;
        denominator_ *= rational.denominator_;
    }

    void sub(Rational rational) {
        numerator_ = numerator_ * rational.denominator_ - rational.numerator_ * denominator_;
        denominator_ *= rational.denominator_;
    }

    void mul(Rational rational) {
        numerator_ *= rational.numerator_;
        denominator_ *= rational.denominator_;
    }

    void div(Rational rational) {
        numerator_ *= rational.denominator_;
        denominator_ *= rational.numerator_;
    }

    void neg() {
        numerator_ = -numerator_;
    }

    void inv() {}

    double to_double() const {
        return numerator_ / (double)denominator_;
    }

    explicit operator bool() const
    {
        return numerator_;
    }

    Rational & operator += (Rational r)
    {
        this->add(r);
        return *this;
    }

    Rational & operator -= (Rational r)
    {
        this->sub(r);
        return *this;
    }

    Rational & operator *= (Rational r)
    {
        this->mul(r);
        return *this;
    }

    Rational & operator /= (Rational r)
    {
        this->div(r);
        return *this;
    }

    Rational operator - () const
    {
        return Rational(-this->numerator_, this->denominator_);
    }

    Rational operator + () const
    {
        return *this;
    }

    int & getNum() { return numerator_; }
    int & getDenom() { return denominator_; }

    int getNum() const { return numerator_; }
    int getDenom() const { return denominator_; }

private:
    int numerator_;
    int denominator_;
};

Rational operator + (Rational r1, Rational const & r2)
{
    return r1 += r2;
}

Rational operator - (Rational r1, Rational const & r2)
{
    return r1 -= r2;
}

Rational operator * (Rational r1, Rational const & r2)
{
    return r1 *= r2;
}

Rational operator / (Rational r1, Rational const & r2)
{
    return r1 /= r2;
}

bool operator == (Rational const & r1, Rational const & r2)
{
    return !(r1 - r2);
}

bool operator < (Rational const & r1, Rational const & r2)
{
    return ((r1.getNum() * r2.getDenom() - r2.getNum() * r1.getDenom()) < 0);
}

bool operator > (Rational const & r1, Rational const & r2)
{
    return r2 < r1;
}

bool operator <= (Rational const & r1, Rational const & r2)
{
    return !(r2 < r1);
}

bool operator >= (Rational const & r1, Rational const & r2)
{
    return !(r1 < r2);
}

bool operator != (Rational const & r1, Rational const & r2)
{
    return !(r1 == r2);
}

using namespace std;

int main() {
    Rational r1(1, 1);
    Rational r2(2, 3);

    cout << (r1 < 1.5) << endl;

    //cout << (+r1).to_double() << endl;
    //cout << (-r1).to_double() << endl;
    //Rational r2(1, 3);
    //Rational r3(5);

    //r1.add(r2);
    //std::cout << r1.to_double() << std::endl;
    //r1.sub(r2);
    //std::cout << r1.to_double() << std::endl;
    //r1.neg();
    //std::cout << r1.to_double() << std::endl;
    //r3.mul(r1);
    //std::cout << r3.to_double() << std::endl;
    //r3.div(r2);
    //std::cout << r3.to_double() << std::endl;

    system("pause>nul");
    return 0;
}