/*
 * File: RationalTest.java
 * -----------------------
 * This program performs a simple test of Rational class.
 *
 * CS1MD3, Nov. 2008
 */

import acm.program.*;

public class RationalTest extends ConsoleProgram {

   public void run() {
      Rational x = new Rational(4, 5);
      Rational y = new Rational(5, 2);
      Rational z = x.multiply(y).subtract(y);
      println(x + " x " + y + " - " + y + " = " + z);
   }

   /**
    * The Rational class is used to represent rational numbers,
    * which are defined to be the quotient of two integers.
    */
   public class Rational {

   /** Creates a new Rational initialized to zero */
      public Rational() {
         this(0);
      }

   /**
    * Creates a new Rational from the integer argument.
    * @param n The initial value
    */
      public Rational(int n) {
         this(n, 1);
      }

   /**
    * Creates a new Rational with the value x / y.
    * @param x The numerator of the rational number
    * @param y The denominator of the rational number
    */
      public Rational(int x, int y){
         int g = gcd(Math.abs(x), Math.abs(y));
         num = x / g;
         den = Math.abs(y) / g;
         if (y < 0) num = -num;
      }

   /**
    * Adds the rational number r to this one and returns the sum.
    * @param r The rational number to be added
    * @return The sum of the current number and r
    */
      public Rational add(Rational r) {
         return new Rational(this.num*r.den + r.num*this.den,
                          this.den*r.den);
      }

   /**
    * Subtracts the rational number r from this one and returns
    * the difference.
    * @param r The rational number to be subtracted
    * @return The result of subtracting r from the current number
    */
      public Rational subtract(Rational r) {
         return new Rational(this.num*r.den - r.num*this.den,
                             this.den*r.den);
      }

   /**
    * Multiplies this number by the rational number r.
    * @param r The rational number used as a multiplier
    * @return The result of multiplying the current number by r
    */
      public Rational multiply(Rational r) {
         return new Rational(this.num*r.num, this.den*r.den);
      }

   /**
    * Divides this number by the nonzero rational number r.
    * @param r The nonzero rational number used as a divisor
    * @return The result of dividing the current number by r
    */
      public Rational divide(Rational r) {
         return new Rational(this.num*r.den, this.den*r.num);
      }

   /**
    * Creates a string representation of this rational number.
    * @return The string representation of this rational number
    */
      public String toString() {
         if (den == 1) {
            return "" + num;
         } else {
            return num + "/" + den;
         }
      }

   /**
    * Calculates the greatest common divisor using Euclid's algorithm.
    * @param First integer
    * @param Second integer
    * @return The greatest common divisor of x and y
    */
      private int gcd(int x, int y) {
         int r = x % y;
         while (r != 0) {
            x = y;
            y = r;
            r = x % y;
         }
         return y;
      }

   /** Private instance variables */
      private int num;      /* The numerator of this Rational */
      private int den;      /* The denominator of this Rational */
   } /* class Rational */
}