ich habe mir einen struct gebastelt (klassen kenne ich noch nicht, dass kommt später noch), der den Zahlenkörper $\mathbb{Q}$ darstellen soll, also die rationalen Zahlen.

Dazu habe ich auch einige Operatoren implementiert. der code sieht wie folgt aus:

#include<iostream>

// Define the new type Rational

struct Rational{
  int n;
  int d; // INV: d!=0
};

// Grundoperatoren

// PRE:  Two value of type Rational
// POST: return value is a Rational representing the summation

Rational operator+ (Rational x, Rational y){
  Rational result;
  result.n=x.n*y.d+y.n*x.d;
  result.d=x.d*y.d;
  return result;
} 

// PRE:  Two value of type Rational 
// POST: return value is a Rational representing the subtraction

Rational operator- (Rational x, Rational y){
  Rational result;
  result.n=x.n*y.d-y.n*x.d;
  result.d=x.d*y.d;
  return result;
} 

// PRE:  Two value of type Rational 
// POST: return value is a Rational representing the product

Rational operator* (Rational x, Rational y){
  Rational result;
  result.n=x.n*y.n;
  result.d=x.d*y.d;
  return result;
} 

// PRE:  Two value of type Rational, y!=0 
// POST: return value is a Rational representing the quotient

Rational operator/ (Rational x, Rational y){
  Rational result;
  result.n=x.n*y.d;
  result.d=x.d*y.n;
  return result;
} 

// Booloperatoren

// PRE:  Two value of type Rational 
// POST: return value is true if a==b

bool operator== (Rational x, Rational y){
  return x.n*y.d==y.n*x.d ;
} 

// PRE:  Two value of type Rational 
// POST: return value is true if a==b

bool operator!= (Rational x, Rational y){
  return !(x.n*y.d==y.n*x.d) ;
}; 

//Rational operator< (Rational x, Rational y){
//  return !(x.n*y.d==y.n*x.d) ;
//} 

// PRE:  A Rational
// POST: Rational has been written on outstream

std::ostream& operator<< (std::ostream& o, Rational x){
  return o << x.n << "/" << x.d;
};

std::istream& operator>> (std::istream& i, Rational x){
  char c; // For the / in input
  return i >> x.n >> c >> x.d;
};

int main ()
{

  // Input

  std::cout << "Your first rational number r:\n";
  Rational r;
  std::cin >> r;

  std::cout << "Your second rational number s:\n";
  Rational s;
  std::cin >> s;

  // Computation and Output

  std::cout << " The sum of 2 Rationals is         " << r+s    << ".\n";
  std::cout << " The subtraction of 2 Rationals is " << r-s    << ".\n";
  std::cout << " The product of 2 Rationals is     " << r*s    << ".\n";
  std::cout << " The division of 2 Rationals is    " << r/s    << ".\n";
  std::cout << " The equality of 2 Rationals is    " <<(r==s)  << ".\n";
  std::cout << " The inequalitz of 2 Rationals is  " <<(r!=s)  << ".\n";

 return 0;
}

Eigentlich glaubte ich, dass dies klappen sollte, wenn ich aber zum bsp.

$r=\frac{2}{3}$ und $s=\frac{5}{6}$ eingebe, bekomme ich als output:

The sum of 2 Rationals is -760672256/0.
The subtraction of 2 Rationals is -760672256/0.
The product of 2 Rationals is 470474752/0.
The division of 2 Rationals is -760672256/0.
The equality of 2 Rationals is 0.
The inequalitz of 2 Rationals is 1.

da läuft doch irgendwas schief?

Merci für die Hilfe,

euer Hugo

std::istream& operator>> (std::istream& i, Rational x){
  char c; // For the / in input
  return i >> x.n >> c >> x.d;
}

werden die Werte in die Kopie geschrieben, welche gleich wieder zerstört wird.
Also "Rational x" jeweils durch "Rational& x" bzw. "const Rational& x" ersetzen und es sollte gehen.

Hugo B