how to overload minus operator to subtract two fractional numbers? - c++

Question

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.

Answer 1

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);
}