This week's book giveaway is in the Servlets forum. We're giving away four copies of Murach's Java Servlets and JSP and have Joel Murach on-line! See this thread for details.

Given the following: public class TrivialApplication { public static void main(String args[]) { double A = 16, B = 5, C = 9; double num; num = ( -B + Math.sqrt( (B*B) - (4*A*C) ) ) / (2*A); System.out.println(num); num = ( -B - Math.sqrt( (B*B) - (4*A*C) ) ) / (2*A); System.out.println(num);

} } The good ole quadratic formula! Of course, when I run the above the displays say NaN. (Not a number, because you can't use Math.sqrt to find the root of a negative number.) What'd I'd like to do is say "If num is NaN, move 0 to num", but how do I use NaN in an expression?

Hey, looks like an assignment I once had. Why dont you just check the discriminant and if its less than zero you will have to create an imaginary number. I dont know however if you are required to do that (it's not a biggie though). discriminant: ( bx * bx ) - ( 4 * ax * c ) so if you want to assign zero (is that what you mean by "move zero to num" ?) instead of creating an imaginary number, try something like this: public class TrivialApplication { public static void main(String args[]) { double A = 16, B = 5, C = 9; double num; //added this part to your code: check whether discr. is neg. nbr //if so, execute following code, otherwise go to "else" if ( ( B * B ) - ( 4 * A * C ) < 0 ) { num = ( -B + Math.sqrt( (B*B) - (4*A*C) ) ) / (2*A); System.out.println(num); num = ( -B - Math.sqrt( (B*B) - (4*A*C) ) ) / (2*A); System.out.println(num); } else num = 0; } } [ March 27, 2004: Message edited by: Ben Buchli ] [ March 28, 2004: Message edited by: Ben Buchli ]