// Ian! D. Allen - idallen@idallen.ca - www.idallen.com
// FunnyMath1 - wrong answers for simple floating comparisons

// Compile and run this program.  Look at the output.
// Explain why all of the outputs are incorrect.
//
// Change the declaration of "f" to "double" (one change) and try again.
// Explain what you see.

public class FunnyMath1 {
    public static void main(String[] args) {
        float f;

        System.out.println( "Inaccurate floating-point comparison attempts" );
        System.out.println( "" );

	// Why do these numbers compare as equal?
	// How big does f need to be before they are not equal?
	     f  = 16777217.0f;
	if ( f == 16777216.0f ) {
	    System.out.println( "The numbers 16777217.0f and 16777216.0f are Equal! WHY?" );
	} else {
	    System.out.println( "Unequal." );
	}
        System.out.println( "Different views of the number 16777217.0f :" );
        System.out.println( "f: " + f );
        System.out.printf( "f: %.40f\n", f );
        System.out.printf( "f: %.40a\n", f );
        System.out.println( "" );

	// Why do these numbers compare as equal?
	// How big does f need to be before they are not equal?
	     f  = 1125899909999999.0f;
	if ( f == 1125899906842624.0f ) {
	    System.out.println( "The numbers 1125899909999999.0f and 1125899906842624.0f are Equal! WHY?" );
	} else {
	    System.out.println( "Unequal." );
	}
        System.out.println( "Different views of the number 1125899909999999.0f :" );
        System.out.println( "f: " + f );
        System.out.printf( "f: %.40f\n", f );
        System.out.printf( "f: %.40a\n", f );
        System.out.println( "" );

	// Why do these numbers compare as equal?
	// How big does f need to be before they are not equal?
	// hex float value 0x1.0p126 is 2**126 - approximately 8.507059e37
	     f  = 0x1.0p126f + 10000000000000000000000000000f;
	if ( f == 0x1.0p126f ) {
	    System.out.println( "The numbers 0x1.0p126f + 10000000000000000000000000000f and 0x1.0p126f are Equal! WHY?" );
	} else {
	    System.out.println( "Unequal." );
	}
        System.out.println( "Different views of the number 0x1.0p126f + 10000000000000000000000000000f :" );
        System.out.println( "f: " + f );
        System.out.printf( "f: %.40f\n", f );
        System.out.printf( "f: %.40a\n", f );
        System.out.println( "" );

    }
}