New to c++ and Overloading operators, unsure how to use the function

Question

Hi I am rather new to C++, I have just started learning it after learning some Java basics. I have pre-existing code were it has overloaded the >> operator, however after watching many tutorials and trying to understand the issue, I thought I would ask here.

Rational cpp file:

 #include "Rational.h"

#include <iostream>




Rational::Rational (){

}



Rational::Rational (int n, int d) {
    n_ = n;
    d_ = d;
}

/**
 * Creates a rational number equivalent to other
 */
Rational::Rational (const Rational& other) {
    n_ = other.n_;
    d_ = other.d_;
}

/**
 * Makes this equivalent to other
 */
Rational& Rational::operator= (const Rational& other) {
    n_ = other.n_;
    d_ = other.d_;
    return *this;
}

/**
 * Insert r into or extract r from stream
 */

std::ostream& operator<< (std::ostream& out, const Rational& r) {
    return out << r.n_ << '/' << r.d_;
}

std::istream& operator>> (std::istream& in, Rational& r) {
    int n, d;
    if (in >> n && in.peek() == '/' && in.ignore() && in >> d) {
        r = Rational(n, d);
    }
    return in;
}}

Rational.h file:

 #ifndef RATIONAL_H_
#define RATIONAL_H_

#include <iostream>
class Rational {
    public:

        Rational ();

        /**
         * Creates a rational number with the given numerator and denominator
         */
        Rational (int n = 0, int d = 1);

        /**
         * Creates a rational number equivalent to other
         */
        Rational (const Rational& other);

        /**
         * Makes this equivalent to other
         */
        Rational& operator= (const Rational& other);

        /**
         * Insert r into or extract r from stream
         */
        friend std::ostream& operator<< (std::ostream &out, const Rational& r);
        friend std::istream& operator>> (std::istream &in, Rational& r);
    private:
    int n_, d_;};

    #endif

The function is from a pre-existing class called Rational which takes two ints as parameters. Here is the function to overload >> :

std::istream& operator>> (std::istream& in, Rational& r) {
        int n, d;
        if (in >> n && in.peek() == '/' && in.ignore() && in >> d) {
            r = Rational(n, d);
        }
        return in;
    }

And I'm trying to use it like this, after seeing a few tutorials. (The error I am getting is "Ambiguous overload for operator>> in std::cin>>n1 :

int main () {
// create a Rational Object.
    Rational n1();
    cin >> n1;
 }

Like I said I'm new to this whole overloading operators thing, and figure someone here would be able to point me in the right direction on how to use this function.

Answer 1

Change Rational n1(); to Rational n1;. You've ran into the most vexing parse. Rational n1(); does not instantiate a Rational object, but declares a function named n1 which returns a Rational object.