overloaded << operator

[ephekt]

Im having a problem passing the correct value to my overloaded << operator. Its displaying some random garbage number. its lines 50 through 55. I tried looking at older posts to answer my question but i could not find a working example of how this works any help would be appreciated thank you

#include <iostream>
using namespace std;

class Rational
{
int num;
int den;

public:
       Rational(); //Default set to 0/1       
       Rational(int num);//set to whole number over 1 
       Rational(int num, int den); //set to any values               
      
       void setnum(int);
       void setden(int);
       void simplify(int num, int den); //simplify rational number 
       void displayRational(); // displays rational number
       
       friend istream& operator>>(istream& ins, Rational& ratnum); //input opperator overload 
       friend ostream& operator>>(ostream& outs, const Rational& ratnum); //output operator overload
       
       friend Rational operator+(const Rational& ratnum1, const Rational& ratnum2); //addition
       friend Rational operator-(const Rational& ratnum1, const Rational& ratnum2); //subtraction
       friend Rational operator*(const Rational& ratnum1, const Rational& ratnum2); //multiply
       friend Rational operator/(const Rational& ratnum1, const Rational& ratnum2); //divide 
       
       friend bool operator<(const Rational & ratnum1, const Rational & ratnum2); //less than
       friend bool operator>(const Rational & ratnum1, const Rational & ratnum2); //greater than
       friend bool operator<=(const Rational & ratnum1, const Rational & ratnum2); //less than or equal to
       friend bool operator>=(const Rational & ratnum1, const Rational & ratnum2); //greater than or equal to 
       friend bool operator==(const Rational & ratnum1, const Rational & ratnum2); //equal to 
};

Rational::Rational(): num(0), den(1)
{}//default constructor

Rational::Rational(int num): num(num), den(1)//sets numerator to whole number
{}

Rational::Rational(int num, int den): num(num), den(den)//sets to any value
{}

//simplify 

void Rational::displayRational()// displays a rational number
{
     cout << num <<"/"<< den << endl;
}
//input
ostream& operator << (ostream& outs, const Rational& RationalNmber) //output
{
  int num, den; 
    
  outs << num << "/" << den ;
  return outs;   
}   

      
       
int main()
{      
 Rational test1, test2(10), test3(1, 2);
 
 test1.displayRational();
 test2.displayRational();
 test3.displayRational();

  
 cout << "\nTest1 equals " << test1;
 cout << "\nTest2 equals " << test2;
 cout << "\nTest3 equals " << test3;
 
 system ("pause");
 return 0;
}

[Gkneeus]

what are the values for num and den? I did not look at your code but they are not defined.

[ephekt]

I had the idea that the constructors would set the values of num and den from the test objects. And I was hoping for the same output as the displayRational function from the overloaded << operator

[Danny Toledo]

ostream& operator << (ostream& outs, const Rational& RationalNmber) //output
{
  int num, den; //uninitialized data
    
  outs << num << "/" << den ; // but you use it as if it were initialized
  return outs;   
}

Maybe you meant something like:

ostream& operator << (ostream& outs, const Rational& RationalNmber) //output
{
  outs << RationalNmber.num << "/" << RationalNmber.den ;
  return outs;   
}

[ephekt]

i tried something like that and i get an error that the variables are private is there a way around this while keeping the the variable private. Do i need a set function or something?

[Danny Toledo]

You forgot to declare ostream& operator << (ostream& outs, const Rational& RationalNmber) as a friend of your class.

[ephekt]

its declared as a friend on line 20 but i forgot i changed the parameter from ratnum to rationalNumber so thats why it didnt work made the one change and added outs << RationalNmber.num << "/" << RationalNmber.den ; to my function and now it works as intended. Thank you Danny for pointing me in the right direction.

[giblit]

Why do you have them all declared as friends? Only a few of them need to be.

[ephekt]

really? in my lame text book it made it sound like any overloaded operator that accesses a private variable needs to be a friend function. Is there an easier way?

[LB]

What giblit means is that you only ever need to implement operator== and operator<, since all other operatoes can be derived from those two.
http://www.cplusplus.com/reference/utility/rel_ops/

[giblit]

Yes sorry I should of been more clear I meant what LB said and also that you shouldn't need friend on your operator+,-,*,/,%

The major ones I can think of where you need friend is for streams with operator ex: ostream operator<< or istream operator>>
and comparison operators like == or <

Also you want to overload the compound operators in your class then use them for the others.

Ex you overload == and < then for > you would put something like return( !(object < object ) && !( object == object ) );

Same goes for the rest of comparison just do some tweaking.

Here is an example

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

#include <iostream> class num { public: num( int value ); num operator+( const num &rhs ); friend std::ostream &operator<<( std::ostream &stm , const num &rhs ); private: int value; }; num::num( int value ) : value( value ){} num num::operator+( const num &rhs) { num result = *this; result.value += rhs.value; return( result ); } std::ostream &operator<<( std::ostream &stm , const num &rhs ) { return( stm << rhs.value ); } int main() { num n1( 10 ) , n2( 20 ); std::cout << ( n1 + n2 ) << std::endl; }

30

[LB]

friend is also convenient for declaring global functions/operators within the scope of templates classes, as it makes the syntax much more concise, even in cases where no access to private or protected members is needed.

[ephekt]

Thank you LB and giblit that makes it a lot easier to understand and will make my program easier to write. Why doesn't my text book say these things?