Nan isn’t like null at all. It doesn’t mean there isn’t anything. It means the result of the operation is not a number that can be represented.
The only option is that operations that would result in nan are errors. Which doesn’t seem like a great solution.
Well, that is what I meant. That NaN is effectively an error state. It’s only like null in that any float can be in this error state, because you can’t rule out this error state via the type system.
Why do you feel like it’s not a great solution to make NaN an explicit error?
Theres plenty of cases where I would like to do some large calculation that can potentially give a NaN at many intermediate steps. I prefer to check for the NaN at the end of the calculation, rather than have a bunch of checks in every intermediate step.
How I handle the failed calculation is rarely dependent on which intermediate step gave a NaN.
This feels like people want to take away a tool that makes development in the engineering world a whole lot easier because “null bad”, or because they can’t see the use of multiplying 1e27 with 1e-30.
Well, I’m not saying that I want to take tools away. I’m explicitly saying that a ieee_754_f64 type could exist. I just want it to be named annoyingly, so anyone who doesn’t know why they should use it, will avoid it.
If you chain a whole bunch of calculations where you don’t care for NaN, that’s also perfectly unproblematic. I just think, it would be helpful to:
- Nudge people towards doing a
NaNcheck after such a chain of calculations, because it can be a real pain, if you don’t do it. - Document in the type system that this check has already taken place. If you know that a float can’t be
NaN, then you have guarantees that, for example, addition will never produce aNaN. It allows you to remove some of the defensive checks, you might have felt the need to perform on parameters.
Special cases are allowed to exist and shouldn’t be made noticeably more annoying. I just want it to not be the default, because it’s more dangerous and in the average applications, lots of floats are just passed through, so it would make sense to block NaNs right away.
Float processing is at the hardware level. It needs a way to signal when an unrepresented value would be returned.
My thinking is that a call to the safe division method would check after the division, whether the result is a NaN. And if it is, then it returns an Error-value, which you can handle.
Obviously, you could do the same with a NaN by just throwing an if-else after any division statement, but I would like to enforce it in the type system that this check is done.
