How about the case where x is (y > 0)? If y is NaN, shouldn't x be boolean-NaN? And shouldn't if(x) throw an exception? Or shouldn't (y > 0) throw an exception if you don't want boolean-NaNs?
> Again, I think it would be _really_ weird for simple value comparisons to throw.
But ... why?
You may say that NaN > 0 is defined as False, but we know that's not how programmers think, most of the time.
In code like if(y > 0) steer_car_to_left() I don't want the compiler or the IEEE standard to make any choices for me! Let it throw, so emergency systems can kick in.
You may not think this is wise, but this is very much how comparisons with NaN are defined.
And I think this is better than exception raising. Again, I think it would be _really_ weird for simple value comparisons to throw.