I want to subtract two fractional numbers using operator overloading. I have write a piece of code in order to accomplish this task:

#include<iostream>
using namespace std;

void HCF(int& a, int& b)
{
    int m, n;

    m = a;
    n = b;

    while (m != n)
    {
        if (m > n)
            m = m - n;
        else
            n = n - m;
    }
    a = a / m;
    b = b / m;
}

class Rational {
    int x1;
    int y1;
public:
    void simplify()
    {
        int m, n, r;
        n = fabs(y1);
        m = fabs(x1);
        while (r = m % n)//Find the Maximum Common Number of m,n
        {
            m = n;
            n = r;
        }
        y1 /= n; // Simplification
        x1 /= n;
        if (y1 < 0) // Convert denominator to positive number
        {
            y1 = -y1;
            x1 = -x1;
        }
    }

    Rational(int num = 0, int denom = 1)
    {
        if (denom) {
            x1 = num;
            y1 = denom;
        }
        else {
            x1 = 0;
            y1 = 1;
        }
    }

    Rational(const Rational& copy)//Copy Constructor
    {
        x1 = copy.x1;
        y1 = copy.y1;

    }

    Rational operator-(const Rational& x) const //Overloaded minus operator
    {
        Rational temp;
        temp.x1 = x1 * x.y1 - x.x1 * y1;
        temp.y1 = y1 * x.y1;
        temp.simplify();
        return temp;
    }

    operator string() const //Overloaded string operator
    {
        int numerator = x1, denominator = y1;
        HCF(numerator, denominator);
        string str;
        if (denominator == 1)
            str = to_string(numerator);
        else
            str = to_string(numerator)   "/"   to_string(denominator);
        return str;
    }
};

int main()
{
    Rational a(5, 1);
    Rational b(3, 4);
    Rational c;
    Rational d;
    Rational x(5, 1);
    c = a - x;
    string expected1 = "0"; //Expected value
    string actual1 = (string)c;//Actual value

    cout << actual1.compare(expected1);//Comparing actual and expected value
    d = c - b;
    string expected2 = "-3/4";
    string actual2 = (string)d;

    cout << actual2.compare(expected2);
}

As we can see, in the main() function, both cout statements should print 0 because when we compare both strings, they must be equal. But the problem is, when I run this program, it prints nothing, and I don't know why.

My operator string() converts an integer fraction into a string. My operator- takes the LCM and finds the final value after subtracting two fractional numbers. In the main() function, I have declared five objects for class Rational, and then I simply perform subtraction and then I compare the expected and actual values, which should return 0 in the cout statement.

I have also used the simplify() member function to check whether the fraction is completely in simpler form or not. For example, it should simplify 2/4 into 1/2.

Where is the mistake? All other functions except operator- are running correctly. The real problem is with the operator-, ie when we perform c=a-x, the value of c would be 0 as a string. Similarly, if we perform d=c-b then the expected value should be -3/4 as a string.

I have also tried to run this code on Google Test, but it fails the test case.

CodePudding user response：

Use this GCD (greatest common divisor) function to implement your HCF function. Yours currently exhibits an endless loop when given 0 as a first argument.

To reduce a fraction, divide numerator and denominator by their greatest common divisor.

This is called the Euclidean algorithm.

template <typename T>
T GCD(T a, T b) {
    while (b != 0)
    {
        T t = a % b;
        a = b;
        b = t;
    }
    return std::max(a, -a);
}