Олимпиадное задание "Калькулятор рациональных дробей"

#include <iostream>
#include <cstdlib>
 
class Fraction
{
private:
    int num, den;
public:
    Fraction();
    Fraction(int);
    Fraction(int,int);
    Fraction(const Fraction&);
    int getNum();
    int getDen();
    void setNum(int);
    void setDen(int);
    friend Fraction reduce(Fraction);
    void reduceit();
    friend std::ostream& operator<<(std::ostream&, Fraction);
    friend Fraction operator+(Fraction,Fraction);
    friend Fraction operator-(Fraction,Fraction);
    friend Fraction operator*(Fraction,Fraction);
    friend Fraction operator/(Fraction,Fraction);
    friend std::istream& operator>>(std::istream&, Fraction&);
    operator float();
};
 
Fraction::Fraction()
{
    num=0; den=1;
}
 
Fraction::Fraction(int n)
{
    num=n; den=1;
}
 
Fraction::Fraction(int n, int d)
{
    setNum(n); setDen(d);
}
 
Fraction::Fraction(const Fraction& it)
{
    *this=it;
}
 
int Fraction::getNum()
{
    return num;
}
 
int Fraction::getDen()
{
    return den;
}
 
void Fraction::setNum(int n)
{
    num=n;
}
 
void Fraction::setDen(int d)
{
    if (d<0)
    {
        num*=-1;
        d*=-1;
    }
    den=(d!=0 ? d : 1);
}
 
int NOD(int m, int n)
{
    if (m==0) return n;
    if (n==0) return m;
    if (m%2==0 && n%2==0)
        return 2*NOD(m/2,n/2);
    if (m%2==0 && n%2!=0)
        return NOD(m/2,n);
    if (m%2!=0 && n%2==0)
        return NOD(m,n/2);
    if (m%2!=0 && n%2!=0)
        return NOD(n,abs(m-n));
    return -1;
}
 
Fraction reduce(Fraction fr)
{
    int del=NOD(fr.num,fr.den);
    return Fraction(fr.num/del,fr.den/del);
}
 
void Fraction::reduceit()
{
    *this=reduce(*this);
}
 
std::ostream& operator<<(std::ostream& stream, Fraction fract)
{
    if (fract.den!=1)
        stream<<'('<<fract.num<<'/'<<fract.den<<')';
    else
        stream<<fract.num;
    return stream;
}
 
Fraction operator+(Fraction arg1, Fraction arg2)
{
    return reduce(Fraction(arg1.num*arg2.den+arg2.num*arg1.den,
        arg1.den*arg2.den));
}
 
Fraction operator-(Fraction arg1, Fraction arg2)
{
    return arg1+Fraction(-arg2.num,arg2.den);
}
 
Fraction operator*(Fraction arg1, Fraction arg2)
{
    return reduce(Fraction(arg1.num*arg2.num,arg1.den*arg2.den));
}
 
Fraction operator/(Fraction arg1, Fraction arg2)
{
    return arg1*Fraction(arg2.den,arg2.num);
}
 
std::istream& operator>>(std::istream& stream, Fraction& fract)
{
    int n,d;
    stream>>n;
    stream.get();
    stream>>d;
    fract=Fraction(n,d);
    return stream;
}
 
Fraction::operator float()
{
    return float(num)/den;
}