Fraction addition in C++ - c++

Question

So basically I am trying to do a fraction class. It will take in the fraction from user input and perform an addition. For example, I type in 1 5 and 1 7 , for the addition it will print out 12/35.
Here is my .h class:
#include <string>
#ifndef _FRACTION_H_
#define _FRACTION_H_
using namespace std;
class Fraction
{
public:
Fraction();
Fraction(int n, int d);
int getNumerator() const;
int getDenominator() const;
void display();
string to_string();
Fraction operator+(Fraction &second);
private:
int numerator;
int denominator;
};
And this is my .cpp file:
#include "Fraction.h"
#include <string>
include <iostream>
using namespace std;
Fraction::Fraction(){}
Fraction::Fraction(int n, int d)
{
this->numerator = n;
this->denominator = d;
}
int Fraction::getNumerator() const
{
return numerator;
}
int Fraction::getDenominator() const
{
return denominator;
}
Fraction Fraction::operator+(Fraction &second)
{
int n1 = getNumerator() * second.getDenominator();
int n2 = second.getNumerator() * getDenominator();
int d = getDenominator() * second.getDenominator();
return Fraction(n1+n2, d);
}
string Fraction::to_string()
{
return (getNumerator() + "/" + getDenominator()) ;
}
And this is my main method:
bool get_input(Fraction &fract);
int main()
{
Fraction fraction1, fraction2;
if (((!get_input(fraction1)) || (!get_input(fraction2))))
cout << "Invalid Input!" << endl;
else
{
// Test harness for Arithmetic Operator Overloading
Fraction result = fraction1 + fraction2;
cout << "Addition = " << result.to_string() << endl;
}
bool get_input(Fraction& fract)
{
int num, den;
cout << "Enter numerator & denominator (separated by space)" << endl;
cin >> num >> den;
if (cin.fail())
return false;
Fraction f(num,den);
fract = f;
return true;
}
}
It's managed to take in the user input. But however, it does not print out the result. Thanks in advance.

Answer 1

There maybe other problems, but the Fraction::to_string()
function is clearly wrong: the types in the return expression
are int, char const* and int. The result of adding these
is a char const*, but given that the string literal is only
two characters long, if the sum of the two int is greater than
two, you have undefined behavior. You need to convert the int
to strings first; the simplest way to do this is to use
std::ostringstream:
std::string
Fraction::to_string()
{
std::ostringstream results;
results << numerator << '/' << denominator;
return results.str();
}
Normally, one would expect a compiler error when you misuse
types like this, but for historical reasons: string literals
have type char const[], not std::string; char const[]
converts almost everywhere to char const*; C++ supports
adding integral values to pointers; and std::string has
a constructor which does an implicit conversion from char
const*.

Answer 2

You use "+" operator between literals ("/") and int in your to_string method
The compiler is trying to do some implicit conversion and it ends up with a point (int + int + char*, best guess is a char*), which is then transformed into a std::string using the correct constructor
Change your method to use stringstream (and you'll have finer control on formatting):
string Fraction::to_string()
{
std::stringstream s;
s << getNumerator() << "/" << getDenominator();
return s.str();
}
reference : http://www.cplusplus.com/reference/sstream/stringstream/