if( x != x ) { ... }

#define x func()
#include <stdio.h>
int i=0;
int func();
main(){
if (x!=x){
printf("I am waiting for my reward\n";
}
}
int func(){
i++;
return i;
}

http://java.sun.com/docs/books/jls/second_edition/html/expressions.doc.html#5198

---SNIP BEGIN---

15.21.1 Numerical Equality Operators == and !=

If the operands of an equality operator are both of primitive numeric type,
binary numeric promotion is performed on the operands (§5.6.2). If the
promoted type of the operands is int or long, then an integer equality test
is performed; if the promoted type is float or double, then a floating-point
equality test is performed.

Note that binary numeric promotion performs value set conversion (§5.1..
Comparison is carried out accurately on floating-point values, no matter
what value sets their representing values were drawn from.
Floating-point equality testing is performed in accordance with the rules of
the IEEE 754 standard:


* If either operand is NaN, then the result of == is false but the result of
!= is true. Indeed, the test x!=x is true if and only if the value of x is
NaN. (The methods Float.isNaN and Double.isNaN may also be used to test
whether a value is NaN.)
* Positive zero and negative zero are considered equal. Therefore, -0.0==0.0
is true, for example.
* Otherwise, two distinct floating-point values are considered unequal by
the equality operators. In particular, there is one value representing
positive infinity and one value representing negative infinity; each
compares equal only to itself, and each compares unequal to all other
values.

Subject to these considerations for floating-point numbers, the following
rules then hold for integer operands or for floating-point operands other
than NaN:

* The value produced by the == operator is true if the value of the
left-hand operand is equal to the value of the right-hand operand;
otherwise, the result is false.
* The value produced by the != operator is true if the value of the
left-hand operand is not equal to the value of the right-hand operand;
otherwise, the result is false.
---SNIP END---

I'm Waiting For My REWARD!! (ONLY A LITTLE TIME!!!)

public class Test {
public static void main(String[] args){

double d1 = -5.0;
double d2 = Math.log(d1); // logarithm of a negative number!!!
if( d2 != d2 )
System.out.println("d2 is Not a Number (NaN)”);

}
}