Brushing Up on my C++

[Krak]

I was brushing up on my C++....overloading operators, that is. So I got to writing the good ol' Fraction class. However, I ran into these errors that I'm not sure how to fix.

class Fraction{
      public:
             int num, den, coef; //numerator, denominator, coefficient
             Fraction():num(1),den(1),coef(0){} //default constructor
             Fraction(int numx, int denomx){
                  num=numx;
                  den=denomx;
                  coef=0;
             }
             ~Fraction(){}
             Fraction& operator+(Fraction& frac2);
             void print(){std::cout<<num<<"/"<<den<<"\n";}
};

Fraction& Fraction::operator+(Fraction& frac2){
          Fraction temp;
          temp.num = (this.num * frac2.den) + (this.den * frac2.num);//new numerator
          temp.den = this.den*frac2.den;
          return temp;
}
      

int main(void){
    Fraction A(1,2);
    Fraction B(2,3);
    Fraction C = A+B;
    C.print();
    std::cin.get();
    return 0;
}

'num' is not a type
'den' is not a type
request for member of non-aggregate type before '*' token

[urban]

- I'm not sure, this operator is "called" from an object of your class, so you can use num and den without "this":

temp.num = (num * frac2.den) + (den * frac2.num);

- If that doesn't work try to write this:

temp.num = ((*this).num * frac2.den) + ((*this).den * frac2.num);

because I think "this" is a pointer to current object.

[prog-bman]

You would use this->variable. not this.variable.

[Krak]

Thank you, gentlemen.

[Ko_Onrad]

Hi,
I don't think that your programm runs correctly 'cause you are returning a reference to a local object.

__Fraction& __
Fraction::operator+(Fraction& frac2){
          Fraction temp;
          temp.num = (this.num * frac2.den) + (this.den * frac2.num);//new numerator
          temp.den = this.den*frac2.den;
          return __temp;__
}

As far as I remember operator+ should return a new Fraction object and operatopr+= should return a reference to *this.

[Krak]

Hi,
I don't think that your programm runs correctly 'cause you are returning a reference to a local object.

__Fraction& __
Fraction::operator+(Fraction& frac2){
          Fraction temp;
          temp.num = (this.num * frac2.den) + (this.den * frac2.num);//new numerator
          temp.den = this.den*frac2.den;
          return __temp;__
}

As far as I remember operator+ should return a new Fraction object and operatopr+= should return a reference to *this.

I actually had warnings about that. What's really so bad about that? I create 'temp' which is a Fraction....and return it, which returns a reference to it....what's so bad about that?

[dwks]

__Fraction& __
Fraction::operator+(Fraction& frac2){

You create a local object. You return a reference to it. But by the time you go to use that reference, the object has gone out of scope! In other words, it no longer exists.

You need to return a copy, not a reference (or pointer).