СПРИНТ № 4 | Перегрузка операторов | Урок 4: Перегрузка операций присваивания 1/2

#include <numeric>
#include <iostream>

using namespace std;

class Rational {
public:
    Rational() = default;

    Rational(int numerator)
        : numerator_(numerator)
        , denominator_(1) {
    }

    Rational(int numerator, int denominator)
        : numerator_(numerator)
        , denominator_(denominator) {
        Normalize();
    }

    int Numerator() const {
        return numerator_;
    }

    int Denominator() const {
        return denominator_;
    }


    Rational& operator+=(Rational r) {
        numerator_ = numerator_ * r.Denominator() + denominator_ * r.Numerator();
        denominator_ = denominator_ * r.Denominator();
        Normalize();
        return *this;
    }

    Rational& operator-=(Rational r) {
        numerator_ = numerator_ * r.Denominator() - denominator_ * r.Numerator();
        denominator_ = denominator_ * r.Denominator();
        Normalize();
        return *this;
    }

    Rational& operator*=(Rational r) {
        numerator_ *= r.Numerator();
        denominator_ *= r.Denominator();
        Normalize();
        return *this;
    }

    Rational& operator/=(Rational r) {
        numerator_ *= r.Denominator();
        denominator_ *= r.Numerator();
        Normalize();
        return *this;
    }


private:
    void Normalize() {
        if (denominator_ < 0) {
            numerator_ = -numerator_;
            denominator_ = -denominator_;
        }
        const int divisor = gcd(numerator_, denominator_);
        numerator_ /= divisor;
        denominator_ /= divisor;
    }

    int numerator_ = 0;
    int denominator_ = 1;
};


std::ostream& operator<<(std::ostream& os, const Rational rat){
    os << rat.Numerator() << '/' << rat.Denominator();
    return os;
}

std::istream& operator>>(std::istream& is, Rational rat){
    char b;
    is >> rat.Numerator() >> b >> rat.Denominator();
    return is;
}

Rational operator+(Rational left, Rational right){
    const int numerator = left.Numerator() * right.Denominator() + right.Numerator() * left.Denominator();
    const int denominator = left.Denominator() * right.Denominator();
    return { numerator, denominator };
}

Rational operator-(Rational left, Rational right){
    const int numerator = left.Numerator() * right.Denominator() - right.Numerator() * left.Denominator();
    const int denominator = left.Denominator() * right.Denominator();
    return { numerator, denominator };
}

Rational operator+(Rational left){
    return {left.Numerator(), left.Denominator()};
}

Rational operator-(Rational left){
    return {-left.Numerator(), left.Denominator()};
}

int main(){
    Rational rat{2,1};
    Rational rat2{3,6};
    Rational rat3;

    cout << rat << endl;

    rat3+=rat;
    cout << rat3 << endl;


    rat3-=rat2;
    cout << rat3;
}