Red Mosquito • View topic

ManiacalClown · **Posted:** Sat Dec 22, 2007 8:41 pm

I have no idea why this amuses me so much, but anyway...

In Java there is a defined constant value known as NaN which when assigned to a variable signifies that it is "not a number." The use for this comes up when you're dealing with floating point, but this is all irrelevant and doesn't make much sense anyway.

What I'm getting at is that at some point it may be necessary to test for a value of NaN (error checking is a good example here). Now, you can be all boring and see if x == Math.NaN resolves to true. And sure, doing that will make your code clear and easy to understand.

However, any sadistic programmer like me loves to make things difficult for others because it validates our pathetic lives. Therefore, I prefer to take advantage of a little known property of our friend NaN. It is the only value for which an identifier becomes unequal to itself. Thus, in order to test for NaN, you can check if x != x resolves to true.

I consider this a much more interesting and confusing way to do things and thus highly recommend it. There's nothing I like more than spitting in the face of the rules of math.

$úñ_DëV|L · **Posted:** Sat Dec 22, 2007 11:02 pm

$úñ_DëV|L · **Posted:** Sun Dec 23, 2007 3:18 am

I like Java's treatment of infinity even better.

Code:

public class Test
{
        public static void main(String[] args)
        {
                double x = Double.POSITIVE_INFINITY;
                double y = Double.NEGATIVE_INFINITY;

                System.out.println("" + (x + y));
                System.out.println("" + (x * y));
                System.out.println("" + (x / y));
                System.out.println("" + (x / x));

                System.out.println("" + (3 / 0.0));
                System.out.println("" + (3 / -0.0));
        }
}

Interestingly, Infinity - Infinity = NaN, Infinity / -Infinity = NaN, and Infinity / Infinity = NaN, but Infinity * -Infinity = -Infinity.

I also like how there's a -0. 3 / 0 = Infinity, and 3 / -0 = -Infinity.

Code:

NaN
-Infinity
NaN
NaN
Infinity
-Infinity

ManiacalClown · **Posted:** Sun Dec 23, 2007 8:13 am

Yeah, floating point is pretty much hilarious in Java.

brainofpea · **Posted:** Sun Dec 23, 2007 4:07 pm

I nearly wet meself.

ManiacalClown · **Posted:** Sun Dec 23, 2007 5:52 pm

Speaking of funny things in Java, I love this quote from The Java Programming Language, Fourth Edition.

Quote:

Enum is actually a generic class defined as Enum<T extends Enum<T>>. This circular definition is probably the most confounding generic type definition you are likely to encounter. We're assured by the type theorists that this is quite valid and significant, and that we should simply not think about it too much, for which we are grateful.

$úñ_DëV|L · **Posted:** Sun Dec 23, 2007 6:08 pm

I like C# better than Java.

ledbutter · **Posted:** Sun Dec 23, 2007 7:25 pm

$úñ_DëV|L wrote:

I like C# better than Java.

i used java in school, but my work is a microsoft shop so i've become quite the c# proponent and it really is very pleasant to work with.

ManiacalClown · **Posted:** Sun Dec 23, 2007 7:36 pm

I need to post a correction to my initial post. Because NaN is the only value that doesn't equal itself, you can't simply do an equality check because...

x == Float.NaN and x == Double.NaN always equal false and
x != Float.NaN and x != Double.NaN always equal true.

Therefore you use Float.isNaN(float) or Double.isNaN(double) which return a boolean value.

Or, of course, you can see if x != x equals true.

And speaking of funny quotes from that book, this one is unintentionally hilarious when taken out of context:

Quote:

Yes the 1.4 specification version is a bug.

I lol'd hard.

noaheb · **Posted:** Sat Feb 02, 2008 4:17 pm

$úñ_DëV|L · **Posted:** Fri Feb 08, 2008 4:14 am

I've been playing around with the more enterprisey Java stuff the last few days, like JSP and Web Services. There's some pretty neat stuff there.

Mecca · **Posted:** Fri Feb 08, 2008 4:36 am

does this mean that we are getting a chatroom?

Echoes · **Posted:** Sun Feb 10, 2008 9:31 am

fuck I haven't used Java in so long. I almost miss it

Stupid Java Programming Trick

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