Reducing Fractions in C++

[lukecovack]

Hello I need to create a program that reduces fractions to lowest terms like 875/1000 = 7/8 I have a function that kind of works and I was wondering if someone couldn't help me fix it. I will include my whole (unfinished program) as I'm never really sure whats relevant and what not to the problem.
here it is:

class CFraction
{
    private:
    int numerator;
    int denominator;
    static int count;
    //void simplify();
    
    public:
    CFraction (int numer = 0, int denom = 1)
    {
        numerator = numer;
        denominator = denom;
    }
    CFraction operator+ (const CFraction&) const;
    CFraction operator- (const CFraction&) const;
    CFraction operator* (const CFraction&) const;
    CFraction operator/ (const CFraction&) const;
    CFraction operator+ (double) const;
    CFraction operator- (double) const;
    CFraction operator* (double) const;
    CFraction operator/ (double) const;
    bool operator== (const CFraction&) const;
    bool operator> (const CFraction&) const;
    bool operator< (const CFraction&) const;
    friend istream& operator>> (istream&, CFraction&);
    friend ostream& operator<< (ostream&, const CFraction&);
    void simplify();
    int getCount();
};

void OpenInputFile(ifstream&);
void OpenOutputFile(ofstream&);
char getYesNo(string);
int showMenu();

int main()
{
    char i;
    int optionanswer;
    int counter = 2;
    bool reduced = true;
    string infileName = "";
    string outfileName = "";
    string str;
    ifstream infile;
    ofstream outfile;
    CFraction f1, f2, f3, f4;

    do
    {
        optionanswer = showMenu();
        switch(optionanswer)
        {
            case 1:
                cin >> f1 >> f2;
                f3 = f1 + f2;
                f3.simplify();
                cout << f3;
                system("Pause");
                break;
            case 2:
            case 3:
            case 4:
            case 5:
            case 6:
            case 7:
            case 8:
            case 9:
            case 10:
            {
                OpenInputFile(infile);
                OpenOutputFile(outfile);
                do
                {
                    i = infile.peek();
                    getline(infile, str);
                    cout << str << endl;
                    switch(i)
                    {
                    }
                }
                while(!infile.eof());
            }
            system("Pause");
            break;
        case 11:
            cin >> f1;
            f1.simplify();
            cout << f1;
            system("Pause");
            break;
        }
    }
    while (optionanswer != 12);
    cout << "Thank You! Godd Bye!" << endl;
    system("Pause");
    infile.close();
    outfile.close();
    return(0);
}
void OpenInputFile(ifstream& infile)
{
    string fileName = "";
    char response = 'z';

    cout << "Please enter the file name for input: ";
    cin >> fileName;
    infile.open(fileName.c_str());
    if(!infile.is_open())
    {
        do
        {
            cout << "Could not open file! " << endl;
            response = getYesNo("Do you want to try to open another?"); 
            cout << endl;
            if (response == 'Y')
            {
                cout << "Please enter the file name for input: ";
                cin >> fileName;
                infile.clear();
                infile.open(fileName.c_str());
            }
            else
            {
                cout << "Thank you and good bye!" << endl;
                system("Pause");
                exit(1);
            }
        }
        while(!infile.is_open());
    }
}
void OpenOutputFile(ofstream& outfile)
{
    string fileName = "";
    char response = 'z';

    cout << "Please enter the file name for output: ";
    cin >> fileName;
    outfile.open(fileName.c_str());
    if(!outfile.is_open())
    {
        do
        {
            cout << "Could not open file! " << endl;
            response = getYesNo("Do you want to try to open another?"); 
            cout << endl;
            if (response == 'Y')
            {
                cout << "Please enter the file name for output: ";
                cin >> fileName;
                outfile.clear();
                outfile.open(fileName.c_str());
            }
            else
            {
                cout << "Thank you and good bye!" << endl;
                system("Pause");
                exit(1);
            }
        }
        while(!outfile.is_open());
    }
}
char getYesNo(string prompt)
{
    char answer;
    do
        {
            cout << prompt << endl;
            cout << "Please enter (Y)es or (N)o: ";
            cin >> answer;
            answer = toupper(answer);
            if ((answer == 'Y') || (answer == 'N'))
            {
                cin.ignore(1, '\n');
                break;
            }
            cin.clear();
            cout << "Incorrect input. ";
            cin.ignore(1, '\n');
        }
        while(true);
    cout << "You entered: " << answer << endl;
    return answer;
}
int showMenu()
{
    int option;
    system("cls");
    cout << "Project3 Test Coding" << endl;
    cout << "                 File Option Menu" << endl;
    cout << "****************************************************" << endl;
    cout << "  1)  Add Fractions" << endl;
    cout << "  2)  Subtract Fractions" << endl;
    cout << "  3)  Multiply Fractions" << endl;
    cout << "  4)  Divide Fractions" << endl;
    cout << "  5)  Add Decimal Value To Fraction" << endl;
    cout << "  6)  Subtract Decimal From Fraction" << endl;
    cout << "  7)  Multiply A Fraction By A Decimal" << endl;
    cout << "  8)  Divid A Fraction By A Decimal" << endl;
    cout << "  9)  Compare Two Fractions" << endl;
    cout << "  10) Read From An Input File and Output To A File" << endl;
    cout << "  11) Simplify A Fraction" << endl; //Testing
    cout << "  12) Exit program" << endl;
    cout << "****************************************************" << endl;
    cout << endl;
    while (true)
        {
            cout << "Please choose an option: ";
            cin >> option;
            if (cin.good() && (option > 0) && (option < 13))
            {
                cin.ignore(1, '\n');
                break;
            }
            cin.clear();
            cout << "Incorrect input. ";
            cin.ignore(1, '\n');
        }
    cout << "You entered: " << option << endl;

    return (option);
}
istream& operator >> (istream& in, CFraction& fract)
{
    cout << "\n  Enter the numerator:  "; in >> fract.numerator;
    cout <<   "  Enter the denominator: "; in >> fract.denominator; 
    return (in);
}
ostream& operator << (ostream& out, const CFraction& fract)
{
    out << "Total:" << endl;
    out << fract.numerator << "/" << fract.denominator << endl;
    return (out);
}
CFraction CFraction::operator + (const CFraction& fract) const
{
    CFraction temp;
    temp.numerator = numerator + fract.numerator;
    temp.denominator = denominator + fract.denominator;
    return (temp);
}
void CFraction::simplify()
{
    int counter = 2;
    bool reduced = true;

    do
    {
        if((numerator >= 2) && (denominator >= 2))
        {
            for(counter;counter<=numerator;counter++)
            {
                if((numerator%counter==0) && (denominator%counter==0))
                {
                    numerator = (numerator/counter);
                    denominator = (denominator/counter);
                    bool reduced = false;
                }
            }
        }
    }
    while(!reduced);
}

[blueberry]

so.... What is the problem exactly?

[R0mai]

Look up gcd (greatest common divisor).

 n    (n/gcd(n,m))
--- = ------------ 
 m    (m/gcd(n,m))

[Mike Sandy]

You could use a recursive function such as:

int gcd(int x,int y)
{

  if(y!=0)
    gcd(y,x%y); //recursive call by using arithmetic rules

  return x; //base case,return x when y equals 0

}

Brute force functions such as the one you are trying to do are harder to read,modify and debug than more efficient,reliable and elegant generic solutions that have already been written.In a professional environment,people wouldn't appreciate those 30 minutes lost
trying to reinvent the wheel,as smart as your code may look.Cheers.