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by xen0 1572 days ago
Should it? It isn't obvious to me at all that throwing an exception in this case is the best behaviour. Throwing an exception when testing a value for 'truthiness' is extremely surprising.

On the other hand, I would strongly discourage 'if(x)' where x is a float that may be NaN purely because the 'correct' behaviour here isn't clear to me.
1 comments
amelius 1572 days ago
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?
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xen0 1572 days ago
That's easy: y > 0 is False, not NaN.

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.

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amelius 1572 days ago
> 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.

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