Beispiel: ``Rational Numbers''

#include <iostream.h>
class Rational
{
private:
  int zaehler, nenner;
public:
  /* GR für die Berechnung des größten
     gemeinsamen Teilers des Nenners;
     kann mit dem ggt kürzen
  */
  int ggt(int, int);
  /* GR berechne das größte gemeinsame
     Vielfache zweier Rationals
  */
  void ggv(Rational& r);
  Rational();
  Rational(int, int n=1);
  friend Rational operator +  (Rational, Rational);
  friend ostream& operator << (ostream&, Rational&);
};

Rational::Rational()
{
  zaehler = 0;
  nenner = 1;
}

Rational::Rational(int Zaehler, int Nenner)
{
  zaehler = Zaehler;
  nenner = Nenner;
}

int Rational::ggt(int a, int b) 
{
  if (b == 0)
    return a;
  else
    return ggt(b, a%b);
}

void Rational::ggv(Rational& r)
{
  int nenner_alt = nenner;
  
  nenner *= r.nenner;
  zaehler *= r.nenner;
  r.nenner *= nenner_alt;
  r.zaehler *= nenner_alt;
}

Rational operator +  (Rational r1, Rational r2)
{
  int g = r1.ggt(r1.nenner, r2.nenner);
  r1.ggv(r2);
  Rational temp(r1.zaehler + r2.zaehler, r1.nenner);
  temp.zaehler /= g;
  temp.nenner /= g;
  return temp;  
}

ostream& operator << (ostream& s, Rational& r)
{
  return s << r.zaehler << '/' << r.nenner;
}

main()
{
  Rational a(1,2), b(1,1), c;
  Rational x(5,8), y(1,6), z;

  
  c = a + b;
  cout << a << "+" << b << "=" << c << endl;

  z = x + y;
  cout << x << "+" << y << "=" << z << endl;

}