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Hi,
I have a problem with one of the comparsions... "lessThanOrEqual" works fine for rational numbers like (3,1), (2,3) etc... But if I try to compare for example (-2,1) and (1,-1) or (2,1) (1,-1) I get wrong answer... I have no idea how to rewrite this piece of code... Please help.

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import javax.swing.JOptionPane;
public class Rational {
	
	public static Rational ZERO = new Rational(0);
	public static Rational ONE = new Rational(1);
	
	private int numerator; // the numerator
	private int denominator; // the denominator
	
		public Rational(int numerator, int denominator) {
		
		  // dealing with x/0 throwing exception 
		  if (denominator == 0) {
            throw new IllegalArgumentException("Denominator must be > 0");
            }
            
		this.numerator = numerator;
		this.denominator = denominator;
		}
		
		// input constructor
		public Rational() {
			
		int num,den;
		String numStr,denStr;
		while(true)
		{
			try
			{
				numStr=JOptionPane.showInputDialog(null,"Input numerator:");
				if (numStr==null)
				System.exit(0);
				num = Integer.parseInt(numStr);
				denStr=JOptionPane.showInputDialog(null,"Input denominator:");
				if (denStr==null)
				System.exit(0); 
				den = Integer.parseInt(denStr);
				if(den == 0)
				{
					// dealing with x/0 throwing exception
					throw new
						IllegalArgumentException("Denominator must be > 0");
				}
				break;
			}
			catch(Exception e)
			{
				System.out.println(e);
			}
			
		}
		
		numerator = num;
		denominator = den;
		
		}
		// double constructor
		public Rational (double d) {
				
				int offset=1;
				while(d*offset!=(int)(d*offset))
				{
					offset*=10;
				}
				numerator=(int)(d*offset);
				denominator=offset;				
					
			}
			
		// string constructor	
		public Rational(String numerator, String denominator) {
			
			int num = Integer.parseInt(numerator);
			int den = Integer.parseInt(denominator);
			if(den == 0)
				
				{	
					// dealing with x/0 throwing exception
					throw new
					IllegalArgumentException("Denominator must be > 0");
				}
				
			this.numerator = num;
			this.denominator = den;
			
		}	
		
		// adding methods
		public Rational add(Rational arg) {
		return new Rational(arg.numerator*denominator+numerator*arg.denominator, denominator*arg.denominator);
		
		}
		
		public Rational add(int i) {
		return new Rational(i*denominator+numerator,denominator);
		
		}	
		
		public Rational add(double d) {
		Rational addedVal = new Rational(d);
		return new Rational(addedVal.numerator*denominator+numerator*addedVal.denominator,denominator*addedVal.denominator);
		
		}
		// end of adding methods			
			
		// multiplication methods
		public Rational mul(Rational arg) {
		return new Rational(arg.numerator*numerator, arg.denominator*denominator);
						
		}
		
		public Rational mul(int i) {
		return new Rational(i*numerator,denominator);
		
		}
		
		public Rational mul(double d) {
		Rational mulVal=new Rational(d);
		return new Rational(mulVal.numerator*numerator, mulVal.denominator*denominator);
		
		}
		// end of multiplications
		
		// subtraction methods
		public Rational sub(Rational arg) {
		return new Rational(arg.numerator*denominator-numerator*arg.denominator, denominator*arg.denominator);
		
		}
		
		public Rational sub(int i) {
		return new Rational(numerator-i*denominator,denominator);
		}
	
		public Rational sub(double d) {
		Rational subVal=new Rational(d);
		return new Rational(subVal.numerator*denominator-numerator*subVal.denominator, denominator*subVal.denominator);
		
		}
		// end of subtraction
		
		// division methods
		public Rational div(Rational arg) {
		if(arg.numerator == 0)
		{
			throw new ArithmeticException("Dividing by 0 bad idea ;)");
		}
		
		int newDen=denominator*arg.numerator;
		int newNum=numerator*arg.denominator;
		return new Rational(newNum, newDen);
		}
	
		public Rational div(int i) {
		if(i == 0)
		{
			throw new ArithmeticException("Dividing by 0 bad idea ;)");
		}
		return new Rational(numerator, denominator/i);
		
		}
		
		public Rational div(double d) {
		if(d == 0)
		{
			throw new ArithmeticException("Dividing by 0 bad idea ;)");
		}
		
		Rational divVal=new Rational(d);
		int newDen=denominator*divVal.numerator;
		int newNum=numerator*divVal.denominator;
		return new Rational(newNum, newDen);
		
		}
		// end of division
		
		// comparison methods
		public boolean equals(Rational arg) {
		return arg.numerator*denominator==arg.denominator*numerator;
		
		}
		
		public boolean lessThan(Rational arg) {
		if (arg.denominator*numerator<denominator*arg.numerator) return true;
		
		else
				return false;
		
		}
	
		public boolean greaterThan(Rational arg) {
		if (arg.denominator*numerator>denominator*arg.numerator) return true;
		
		else
				return false;
		
		}
		// problem with (-2,1), (1,-1) etc...
		public boolean lessThanOrEqual(Rational arg) {
		if (arg.denominator*numerator<=denominator*arg.numerator) return true;
		
		else
				return false;
		
		}
	
		public boolean greaterThanOrEqual(Rational arg) {
		if (arg.denominator*numerator>=denominator*arg.numerator) return true;
		
		else
				return false;
				
		}
		// end of comparsion
		
       public String toString()
       {
          Rational red=reduce();
          return red.numerator+"\\"+red.denominator;
       }
       // Working reduction
       // I don't know how to implement "void reduce()"
       private Rational reduce() //
       {
          int n = numerator;
          int gcd = denominator;
          int tmp;
          if(n < gcd)
          {
             tmp = n;
             n = gcd;
             gcd = tmp;   
          }
          while(n!=0)
          {
             tmp = n;
             n = gcd%n;
             gcd = tmp;
          }
          return new Rational(numerator/gcd,denominator/gcd);
       }
		
		public static void main(String[] args) {
			
			Rational a=new Rational();
			Rational i=new Rational(-2,1);
			Rational d=new Rational(1,-1);
			Rational s=new Rational("25", "75");
			System.out.println(i.lessThanOrEqual(d));
			
			
		/* Printing results	
		JOptionPane.showMessageDialog(null,"DEFINED RATIONAL NUMBERS:\n-------------------------------------------\n" 
		+ "User rational number: "+a + "\nRational [1] (integer): "+i + "\nRational [2] (double): "+d + "\nRational [3] (string): "+s 
		+ "\n-------------------------------------------\nADDITION:\n-------------------------------------------\n"
		
		// Addition
		+a + " + " +i+ " = " + a.add(i) + "\n"	 
		+a + " + " +d+ " = " + a.add(d) + "\n" 
		+a + " + " +s+ " = " + a.add(s) + "\n" 		 
		+d + " + " +s+ " = " + d.add(s) + "\n"
			
		+ "-------------------------------------------\nSUBTRACTION:\n-------------------------------------------\n"
			
		// Subtraction
		+i + " - " +a+ " = " + a.sub(i) + "\n"	 
		+d + " - " +a+ " = " + a.sub(d) + "\n" 
		+s + " - " +a+ " = " + a.sub(s) + "\n" 	 
		+d + " - " +s+ " = " + s.sub(d) + "\n"
			
		+ "-------------------------------------------\nMULTIPLICATION:\n-------------------------------------------\n"
		
		// Multiplication	
		+a + " * " +i+ " = " + a.mul(i) + "\n"	 
		+a + " * " +d+ " = " + a.mul(d) + "\n" 
		+a + " * " +s+ " = " + a.mul(s) + "\n" 	 
		+d + " * " +s+ " = " + s.mul(d) + "\n"	 	 		

		+ "-------------------------------------------\nDIVISION:\n-------------------------------------------\n"
		
		// Division	
		+a + " : " +i+ " = " + a.div(i) + "\n"	 
		+a + " : " +d+ " = " + a.div(d) + "\n" 
		+a + " : " +s+ " = " + a.div(s) + "\n" 	 
		+d + " : " +s+ " = " + s.div(d) + "\n"

		+ "-------------------------------------------\nCOMPARSIONS:\n-------------------------------------------\n"
		
		// Comparsions	
		+a + " = " +i+ " = " + a.equals(i) + "\n"	 
		+a + " < " +d+ " = " + a.lessThan(d) + "\n" 
		+a + " > " +s+ " = " + a.greaterThan(s) + "\n" 	 
		+a + " <= " +s+ " = " + a.lessThanOrEqual(s) + "\n"	
		+a + " >= " +d+ " = " + a.greaterThanOrEqual(d) + "\n", "Results",
		JOptionPane.PLAIN_MESSAGE);
		*/		
		}	
	}

Refactorings

No refactoring yet !

F9a9ba6663645458aa8630157ed5e71e

Ants

January 7, 2010, January 07, 2010 08:12, permalink

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Huh? lessThanOrEqual() doesn't work, but lessThan() works for the same inputs? They should both succeed or both fail since they are basically doing the same operation. This points to the most basic improvement that you can do to this code: instead of repeating yourself, try to re-use functions.

Anyway the issue is that you should be consistent about where you keep the sign of ration number. Consistently store the sign with the numerator (or the denominator). This will allow your cross multiplication to keep the sign on the appropriate sides of the comparison.

Your refactoring





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