/*
 *  =========================================================================
 *  NumericalErrorConditions.java: This program illustrates Java's capability
 *  in handling error conditions related to:
 *
 *    1. Overflow and underflow of numbers (i.e., Infinity and -Infinity),
 *    2. Arithmetic expressions where the result is not-a-number (i.e., NaN).
 *
 *  Written By: Mark Austin                                     October, 2007
 *  =========================================================================
 */

import java.lang.Math;

public class NumericalErrorConditions {
    public static void main( String args[] ) {
        double dA = 0.0;
        double dB, dC;

        // Format and print data values ....

        System.out.printf("dA = %8.3f\n", dA );

        // Generate error conditions in arithmetic expressions ...

        System.out.println("Simulate Error Conditions ... ");
        System.out.println("============================= ");

        System.out.printf("Divide by zero:  ( 1/0.0) = %8.3f\n",  1.0/dA );
        System.out.printf("Divide by zero:  (-1/0.0) = %8.3f\n", -1.0/dA );
        System.out.printf("  Not a number: (0.0/0.0) = %8.3f\n",   dA/dA );

        // Generate variables that store error conditions....

        System.out.println("Variables that store error conditions ... ");
        System.out.println("========================================= ");

        dB = 1.0/dA;
        System.out.printf("dB = 1.0/dA = %8.3f\n",  dB );
        dC = dA/dA;
        System.out.printf("dC =  dA/dA = %8.3f\n",  dC );

        // Test for variables that are assigned error conditions....

        System.out.println("Test for variable values containing error conditions ... ");
	System.out.println("======================================================== ");
  
        if( dB == Double.POSITIVE_INFINITY )
            System.out.println("***  dB is equal to +Infinity" );
        else
            System.out.println("***  dB is not equal to +Infinity" );

        if( dB == Double.NEGATIVE_INFINITY )
            System.out.println("***  dB is equal to -Infinity" );
        else
            System.out.println("***  dB is not equal to -Infinity" );

        if( dB == Double.NaN )
            System.out.println("***  dB is Not a Number" );
        else
            System.out.println("***  dB is a Number" );

        // ===================================================================
        // Now let's see what happens when evaluation of arithmetic expression
        // inadvertently generates an error.
        // ===================================================================

        System.out.println("Evaluate y(x) for range of x values");
        System.out.println("===================================");

        for ( double dX = 1.0; dX <= 5.0; dX = dX + 0.5 ) { 
              double dY = 1.0 + 1.0/(dX - 2.0) - 1.0/(dX - 3.0) + (dX-4.0)/(dX-4.0);
              System.out.printf(" dX = %4.1f   y(dX) = %8.3f\n", dX, dY );
        }
        System.out.println("===================================");

    }
}