Issues with constructors for class

[Cat32]

I'm trying to write a program that simplifies fractions. The problems is that when I put in a denominator of 0, It's supposed to give an error message. I put it in my constructor but it's not using it at all. Any ideas as to what I'm doing wrong. I'm beating my head against a wall at this point.


#include <iostream>
#include <cmath>
#include <sstream>
using namespace std;

class Fraction
{
private:
int numerator;
int denominator;
public:

Fraction()
{
numerator=1;
denominator=1;
}

Fraction(int num, int denom)
{
numerator = num;
denominator = denom;

if (denominator==0)
{
cout << "Error: Can't divide by 0";
exit(0);
}
}

void setNumerator(double num)
{
numerator=num;
}

void setDenominator(double denom)
{
denominator=denom;
}

double toDecimal(double num, double denom)
{
return num/denom;
}

string toString(double number)
{
string String=static_cast<ostringstream*>(&(ostringstream() << number) )->str();
return String;
}

double reduce(double num, double denom)
{
if(denom==0)
return num;

else
return reduce(denom, fmod(num, denom));
}
};

int main()
{
double num;
double denom;
Fraction frac;

cout << "Please enter the numerator: ";
cin >> num;
frac.setNumerator(num);

cout << "Please enter the denominator: ";
cin >> denom;
frac.setDenominator(denom);


cout << "Your fraction is: " << num << "/" << denom << "." << endl;
cout << "As a decimal your fraction is: " << frac.toDecimal(num, denom) << "." << endl;
cout << "Your fraction as a string is: " << frac.toString(num) << "/" << frac.toString(denom) << "." << endl;
int gcd = frac.reduce(num, denom);
cout << "Your fraction reduced is: " << num/gcd << "/" << denom/gcd << "." << endl;

return 0;
}

[mutexe]

Morning. It's because when you instantiate your Fraction you're calling the 'wrong' constructor:

This:
Fraction frac;
calls this:

Fraction()
{
  numerator=1;
  denominator=1;
}

not this:

	Fraction(int num, int denom)
	{
		numerator = num;
		denominator = denom;

		if (denominator==0)
		{
			cout << "Error: Can't divide by 0";
			exit(0);
		}
	}

Therefore you want to do something like this:

	double num;
	double denom; 
	

	cout << "Please enter the numerator: ";
	cin >> num;
	//frac.setNumerator(num);

	cout << "Please enter the denominator: ";
	cin >> denom;
	//frac.setDenominator(denom);
	Fraction frac(num, denom);

also be wary stuff like this, particularly when dividing:

numerator=num;

numerator is an int, but num is a double for some reason.