Rational Numbers Assignment Adding

We have everything done except we do not know how to do the adding of rational numbers. can you help?

Code:

#include "Rational.h"
#include "math.h"
#include <iostream>

using namespace std;

Rational::Rational()
{
     numerator = denominator = 1;
}

Rational::Rational(int N, int D)
{
    numerator = N;
    denominator = D;
} 

int Rational::getN()
{
              return numerator;
}

int Rational::getD()
{
              return denominator;
}

int Rational::multiply(Rational rational2)
{
    int finalN =getN()*rational2.getN();
    int finalD =getD()*rational2.getD();
    Rational rational(finalN,finalD);
    simplify(rational);
} 

int Rational::divide(Rational rational2)
{
    int finalN =getN()*rational2.getD();
    int finalD =getD()*rational2.getN();
    Rational rational(finalN,finalD);
    simplify(rational);
}

int Rational::add(Rational rational2)
{
int tempN = getN()*rational2.getD();
int tempD = getD()*rational2.getN();
int finalN = tempN*tempD 
int finalD = 
Rational rational(finalN,finalD);
simplify(rational);
}

void Rational::simplify(Rational rational)
{
     int x=rational.getN();
     int y=rational.getD();
     int z;
     while (y!=0)
     {
           z=x%y;
           x=y;
           y=z;
     }
     int finalN=rational.getN()/x;
     int finalD=rational.getD()/x;
     Rational rationalnew (finalN,finalD);
     cout <<finalN<<"/"<<finalD<<endl;
}
     
        
bool Rational::compare(Rational rational2)
{
     float initial=(float)getN()/getD();
     float final= (float)rational2.getN()/rational2.getD();
     if (initial==final) return true;
     else return false;
}

Simply put, multiply the nominators by the cross denominator and get a common denominator by multiplying the denominators together.

Adding and Subtracting Rational Functions - Free Math Help

An easy way to find a common denominator is by multiplying the denominators together:

Code:

1/4 + 3/9
9/36 + 12/36 // 1 times 9 = 9. 3 times 4 = 12. 4 times 9 equal 36

Knowing this, you should be able to find or make a function that does this for you.
If you need more help, just reply and I'll write some code.

Code:

int Rational::multiply(Rational rational2)
{
    int finalN =getN()*rational2.getN();
    int finalD =getD()*rational2.getD();
    Rational rational(finalN,finalD);
    simplify(rational);
}

Why not make simplify() a function that operates on "this" rational? That makes more sense to me. Unless the interface is part of the assignment that you can't change, of course.

Code:

if (initial==final) return true;

This is dangerous because
1. the difference can be smaller than representable in a float
2. floats (and doubles) should generally not be compared with == because not all values can be represented with infinite precision

For this function, I would just simplify both functions, and see if the denominators and numerators are equal.

Also, for simplify(), I would "float" the negative sign to the top, if there is one. So "1/(-4) == (-1)/4" will be true.

If you need more help, just reply and I'll write some code.

Just in case... please don't write people's homework for them.

Originally Posted by cyberfish

For this function, I would just simplify both functions, and see if the denominators and numerators are equal.

I assume you mean "fraction" not "function." I would not simplify them. I'd just check if numer1 * denom2 == numer2 * denom1.

Yes (to both) of course .