// rational.h
#ifndef RATIONAL_H
#define RATIONAL_H

// class RationalNumber definition
class RationalNumber {

public:
   RationalNumber( int = 0, int = 1 ); // default constructor

   const RationalNumber operator+( const RationalNumber& );
   /* Write prototype for operator- */
   const RationalNumber operator-( const RationalNumber& );
   const RationalNumber operator*( const RationalNumber& );
   const RationalNumber operator/( const RationalNumber& );
   bool operator>( const RationalNumber& ) const;
   bool operator<( const RationalNumber& ) const;
   bool operator>=( const RationalNumber& ) const;
   /* Write prototype for operator <= */
   bool operator<=( const RationalNumber& ) const;
   bool operator==( const RationalNumber& ) const;
   bool operator!=( const RationalNumber& ) const;

   void printRational() const;

private:
   int numerator;
   int denominator;
   void reduction();

}; // end class RationalNumber

#endif // RATIONAL_H

[c/c++]

// rational.cpp 
#include <cstdlib>

#include <iostream> 

using std::cout; 
using std::endl; 

#include "rational.h"

// constructor
RationalNumber::RationalNumber( int n, int d )
{
   numerator = n;
   denominator = d;
   reduction();
   
   /* Write function call to reduction function */

} // end class RationalNumber constructor

/* Write definition for overloaded operator+ */
const RationalNumber RationalNumber::operator +( const RationalNumber &s )
{
	RationalNumber add;

	add.numerator = numerator * s.denominator + denominator * s.numerator;
    add.denominator = denominator * s.denominator;
    add.reduction();

   return add;
}

// function operator- definition
const RationalNumber RationalNumber::operator-(
   const RationalNumber &s )
{
   RationalNumber sub;

   sub.numerator = numerator * s.denominator - denominator *
      s.numerator;
   sub.denominator = denominator * s.denominator;
   sub.reduction();
   return sub;

} // end function operator- 

/* Write definition for overloaded operator * */
const RationalNumber RationalNumber::operator *( const RationalNumber &k)
{
	RationalNumber mult;
	mult.numerator = numerator * k.numerator;
	mult.denominator = denominator * k.denominator;

	return mult;
}

// function operator/ definition
const RationalNumber RationalNumber::operator/( 
   const RationalNumber &d )
{
   RationalNumber divide;

   if ( divide.numerator = 0 ) 
   {  
      divide.numerator = numerator * d.denominator;
      divide.denominator = denominator * d.numerator;
      divide.reduction();

   } // end if

   else {
      cout << "Divide by zero error: terminating program\n";
      exit( 1 );   // cstdlib function

   } // end else

   return divide;

} // end function operator/

// function operator> definition
bool RationalNumber::operator>( const RationalNumber &gr ) const
{
   // compare double values of two rational numbers
   if ( static_cast< double >( numerator ) / denominator > 
        static_cast< double >( gr.numerator ) / gr.denominator )
      return true;

   else
      return false;

} // end function operator>

// function operator< definition
bool RationalNumber::operator<( const RationalNumber &lr ) const
{
   return !( *this > lr );

} // end function operator<

// function operator>= definition
bool RationalNumber::operator>=( const RationalNumber &rat ) const
{  
   return *this == rat || *this > rat;

} // end function operator>=
bool RationalNumber::operator<=( const RationalNumber &rat ) const
{
	return *this == rat || *this < rat;
}

/* Write definition for operator <= */

/* Write definition for operator == */
bool RationalNumber::operator==( const RationalNumber &iq ) const
{
	if ( *this == iq )
		return true;

	return false;
	
}

/* Write definition for operator != */
bool RationalNumber::operator!=( const RationalNumber &iq ) const
{
	if ( *this == iq )
		return false;

	return true;
}

// function printRational definition
void RationalNumber::printRational() const
{
   if ( numerator == 0 )         // print fraction as zero
      cout << numerator;

   else if ( denominator == 1 )  // print fraction as integer
      cout << numerator;

   else
      cout << numerator << '/' << denominator;

} // end function printRational

// function reduction definition
void RationalNumber::reduction()
{
   int smallest;
   int gcd = 1;  // greatest common divisor

   smallest = ( numerator < denominator ) ? numerator 
      : denominator;

   for ( int loop = 2; loop <= smallest; ++loop )

       if ( numerator % loop == 0 && denominator % loop == 0 )
          gcd = loop;

   numerator /= gcd;
   denominator /= gcd;

} // end function reduction

// driver.cpp
#include <iostream> 

using std::cout;
using std::endl; 

#include "rational.h"

int main()
{
   RationalNumber c( 7, 3 );  
   RationalNumber d( 3, 9 );
   RationalNumber x;

   c.printRational();
   cout << " + " ;
   d.printRational();
   cout << " = ";
   x = c + d;
   x.printRational();

   cout << '\n';
   c.printRational();
   cout << " - " ;
   d.printRational();
   cout << " = ";
   /* Write statement to subtract c from d and assign the result to x */
   d - c == x;
   x.printRational();

   cout << '\n';
   c.printRational();
   cout << " * " ;
   d.printRational();
   cout << " = ";
   /* Write statement to multiply c and d and assign the result to x */
   c * d == x;
   x.printRational();

   cout << '\n';
   c.printRational();
   cout << " / " ;
   d.printRational();
   cout << " = ";
   x = c / d;
   x.printRational();

   cout << '\n';
   c.printRational();
   cout << " is:\n";

   cout << ( ( c > d ) ? "  > " : "  <= " );
   d.printRational();
   cout << " according to the overloaded > operator\n";

   cout << ( ( c < d ) ? "  < " : "  >= " );
   d.printRational();
   cout << " according to the overloaded < operator\n";

   cout << ( ( c >= d ) ? "  >= " : "  < " );
   d.printRational();
   cout << " according to the overloaded >= operator\n";

   cout << ( ( c <= d ) ? "  <= " : "  > " );
   d.printRational();
   cout << " according to the overloaded <= operator\n";

   cout << ( ( c == d ) ? "  == " : "  != " );
   d.printRational();
   cout << " according to the overloaded == operator\n";

   cout << ( ( c != d ) ? "  != " : "  == " );
   /* Write statement to print d */
   cout << " according to the overloaded != operator" << endl;

   return 0;

} // end main