Fraction Class


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This is a simplistc implementation of a fraction class, along with a sample program to demonstrate how to use it. The main( ) function, and the class are defined in the same .cpp source file for simplicity. The class has simple operators like +, and - defined to enable and facilitate easy operation of fraction objects.


You can copy the code between the 2 HORIZONTAL LINES, paste it and save it as ASCII test, and compile it with a standards compliant C++ compiler such as g++.
#include <iostream>
#include <string> //needed for "system", dunno know why???
#include <cmath>

//#define MY_DEBUG
#define GNU_LINUX
//#define WIN32_CRAP


using namespace std;


class fraction {
private:
  int num, den;
  int size;
  int* primes;

public:
  fraction (int n = 0, int d = 0):num(n), den(d) { primes = reinterpret_cast<int*>(0); } //constructor
  fraction::fraction (const fraction& f);

  void generate_primes (int cnt = 100);
  void remove_prime (fraction& f);



#ifdef MY_DEBUG
  void disp_prime (void) const
  {
    for (int i = size-1; i >= 0; i--)
      cout<<"   "<<primes[i];
    cout<<endl;

  }
#endif


  fraction& operator+= (const fraction& f);
  fraction& operator-= (const fraction& f);
  fraction& operator= (const fraction& f);
  fraction& operator= (const int& elem);
  ~fraction () { if (primes != reinterpret_cast<int*>(0)) delete[] primes; } //destuctor.

  friend fraction operator+ (const fraction&, const fraction&);
  friend fraction operator- (const fraction&, const fraction&);

  int numerator (void) const
  {
    return (num);
  }

  int denominator (void) const
  {
    return (den);
  }

};



fraction::fraction (const fraction& f):num(f.num), den(f.den), size(f.size)
  {
    primes = new int[f.size];

    for (int i = 0; i < f.size; i++)
      {
        primes[i] = f.primes[i];
      }
  }



fraction& fraction::operator= (const int& elem)
{
  num = elem;
  den = 1;
  return (*this);
}



fraction& fraction::operator= (const fraction& f)
{
#ifdef MY_DEBUG
  cout<<endl<<"In op+ const fraction& f"<<endl;
#endif

  num = f.num;
  den = f.den;
  return (*this);
}



fraction& fraction::operator+= (const fraction& f)
{
  num = num * f.den + f.num * den;
  den = den * f.den;

  if (num == 0) den = 1;
  else  remove_prime (*this);

  if (num < 0 && den < 0)
    {
      num = -num;
      den = -den;
    }

  return (*this);
}




fraction& fraction::operator-= (const fraction& f)
{
  num = num * f.den - f.num * den;
  den = den * f.den;

  if (num == 0) den = 1;
  else remove_prime (*this);

  if (num < 0 && den < 0)
    {
      num = -num;
      den = -den;
    }

  return (*this);
}



//generates 100 primes by default.
void fraction::generate_primes (int cnt = 100)
{
#ifdef MY_DEBUG
  cout<<endl<<"In generate_prime "<<cnt<<endl;
#endif

  int n = 1;
  int f;
  if (primes != reinterpret_cast<int*>(0))
    {

#ifdef MY_DEBUG
      cout<<endl<<"In generate_prime prime: not init, now -> init. "<<cnt<<endl;
#endif

      delete[] primes;
      primes = new int[cnt];
    }
  else primes = new int[cnt];


  for (int i = 0; i < cnt; )
    {
      n++;
      if (n != 2 && n % 2 == 0) continue;

      f = 0;

      for (int j = static_cast<int>(sqrt (static_cast<double>(n))); j > 1; j--)
          if (n % j == 0) f++;

      if (f == 0)
          primes[i++] = n;
    }

  size = cnt;

}




//removes common prime factors form the numerator and denominator.
void fraction::remove_prime (fraction& f)
{
  int temp;

  for (int i = 0; i < size; i++)
    {
      temp = primes[i];

      if (abs(num) >= temp && abs(den) >= temp)
        {
          if (num % temp == 0 && den % temp == 0)
            {
              num /= temp;
              den /= temp;
              i--;
            }
        }
      else return;

    }
}





fraction operator+ (const fraction& f1, const fraction& f2)
{
  fraction retval = f1;
  retval += f2;
  return (retval);
}




fraction operator- (const fraction& f1, const fraction& f2)
{
  fraction retval = f1;
  retval -= f2;
  return (retval);
}





int main()
{

#ifdef GNU_LINUX
  system ("clear");
#endif

#ifdef WIN32_CRAP
  system ("cls");
#endif

  int top1, bottom1, top2, bottom2;
  fraction f1, f2, f3;
  char loop;
  do
    {
      cout << "Input numerator: ";
      cin >> top1;
      cout << "Input denominator: ";
      cin >> bottom1;
      cout << "Input numerator: ";
      cin >> top2;
      cout << "Input denominator: ";
      cin >> bottom2;
      cout <<top1<<"/"<<bottom1<<endl<<top2<<"/"<<bottom2<<endl;
      cout << endl;

      f1 = fraction (top1, bottom1);
      f2 = fraction (top2, bottom2);
      f1.generate_primes (); // by default, 100 primes are generated.
      f2.generate_primes (); // by default, 100 primes are generated.

      f3 = f1 + f2; // isn't this cleaner than add= (whatever)..........

      cout<<endl<<"Sum = "<<f3.numerator ()<<"\\"<<f3.denominator ()<<endl;

      f3 = f1 - f2; // same for this.

      cout<<endl<<"Difference = "<<f3.numerator ()<<"\\"<<f3.denominator ()<<endl;

#ifdef MY_DEBUG
      f1.disp_prime ();
#endif


      // add=((top1*bottom2)+(bottom1*top2))/(bottom1*bottom2);
      //cout <<add<<endl;
      //sub=((top1*bottom2)-(bottom1*top2))/(bottom1*bottom2);
      //cout <<sub<<endl;

      cout << "Another fraction?(Y or N):";
      cin >> loop;
      cout << endl;
    } while(loop=='Y'|| loop=='y');// the | is a bitwse OR operator, not logical OR.

  return 0;
}










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