//Rational operator*(const Rational & r) const {return Rational(ToDouble()*r.ToDouble());}
//Rational operator/(const Rational & r) const {return Rational(ToDouble()/r.ToDouble());}
- Rational operator-() const {Rational r(*this); r.P = -r.P;}
+ Rational operator-() const {Rational r(*this); r.P = -r.P; return r;}
Rational & operator=(const Rational & r) {P = r.P; Q = r.Q; Simplify(); return *this;}
Rational & operator+=(const Rational & r) {this->operator=(*this+r); return *this;}
Rational & operator-=(const Rational & r) {this->operator=(*this-r); return *this;}