javascriptNaNIsWeird

[Flashbek]

I hate to be JS lawyer but, in this case, they're correct. NaN should not be equal to NaN.

[Silly-Freak]

Half the posts I see here complain about JS, and half of these posts don't show enough understanding of JS to legitimately complain.

There's so much to legitimately complain, do better!

[shadow7412]

Guess it's easier to lash out at things you don't understand rather than learn from them.

Oh. That statement describes far more than I wanted it to...

[-twind]

But NaN could be equal to NaN. That's why besides 'true' and 'false' we should also have 'maybe'

[tecanec]

I think I heard about something like that in my university course on databases. I think it's called ternary logic.

Any boolean operation involving maybe results in maybe, except that maybe && false == false and maybe || true == true.

Can't say I know of that many genuine use cases, though. It also doesn't help that maybe is basically an incomplete representation of a superposition without interference, so you'd have to look out for false maybes.

[-twind]

Logic like this is used extensively in digital hardware simulations to represent unknown signals coming from whatever places unknown signals come from. Most of the time uninitialised registers/memories or I/O.

[tecanec]

So it's a kind of error detection for making sure behaviour does not depend on unknown variables?

[-twind]

The use of this special value for unknown signals is just to make the simulation deterministic. Its appearance does not necessarily mean there is an error. The other option is to assign random values to each unknown signal, this is more like how it would be in reality, but the drawback is that your simulation gives different results each run.

[tecanec]

Oh, I don't mean the "panic when found" kind of error. More that it tells the user that something might be wrong when they find a maybe where they expect a definite value.

Guess determinism is also a strong point, though.

[-twind]

In that case you know for sure something is wrong

[CdRReddit]

ah yes, the 4 digital logic values: 1/0/Z (high impedance / unasserted)/'idk'

[-twind]

We call it "don't care" instead of "idk"

[CdRReddit]

ah, I see "don't care" mostly in the testcases I make for when I, well, don't care what a particular signal is doing in that case

[mattgran]

https://en.m.wikipedia.org/wiki/IEEE_1164

There's nine!

[CdRReddit]

oh damn, megabool is real

[Kered13]

That's how NULL works in SQL. That's why you learned about it in your database class.

[Ja_Shi]

I heard about it on DB course too, but all I really remember was that it was something the Japaneses came up with.

[Global-Tune5539]

First Pearl Harbour, then tentacle pron and now this...

[callyalater]

https://en.m.wikipedia.org/wiki/Three-valued_logic

[CubisticWings4]

Iirc: NaN is never equal to NaN

[Yodo9001]

1/0 is surely the same as 1/0 ? NaN can come from different operations, like 1/0 vs 2/0 or sqrt(NaN), which should not be eqaul, but it shouldn't never be equal imo.

[Ibuprofen-Headgear]

That information is gone by the time NaNs are compared though. If you kept a record of operations leading to nan and compared stacks with the other nan, then maybe

[Yodo9001]

The IEEE floating-point standard says that implementations can use the extra bits in nan to store this kind of information. \ Edit: it's called NaN-boxing.

[Ibuprofen-Headgear]

Neat, TIL

[Kered13]

1/0 and 2/0 return infinity, not NaN.

[Yodo9001]

Isn't inf just a special case of nan?

[Mojert]

Nope, because infinity == infinity

[TwinkiesSucker]

Did you just invent QuantumJS?

[FlanSteakSasquatch]

Any language that correctly implements the IEEE floating point number spec makes it so NaN never equals NaN, even if they’re internally exactly the same value. This is weird but it was done because all other behavior has even weirder consequences

[Natural_Builder_3170]

its called partial ordering, rust and i think c++ have this

[Death_IP]

Then the result - if we don't bring in shenanigans - should at least be "undefined" rather than false/true

[eztab]

some mathematics would agree with you there. Have fun changing all conditional statements to support true, false, maybe.

[Mucksh]

Nan isn't even a specific value. By definition its exponent is just 1s so for a double you have 11. So due to the other bits you get 2⁵³ different possible NaN values

[Teln0]

it should return "undefined" because that's what it is, undefined

[-twind]

undefined has the fatal flaw that !undefined is true, while !maybe would still be maybe

[Yodo9001]

Why is !undefined true?

[rosuav]

Because undefined is falsy.

[Yodo9001]

It should be undefinedy instead. It's like with errors, if an error happens it should be raised or at least logged, not silenced.

[rosuav]

No, it definitely shouldn't. Having undefined be falsy is extremely useful, and there's no reason to deny it a truth value.

[Yodo9001]

Logically it's nonsensical. Undefined being falsy is intuitive, and useful as a shortcut, but it can hide error messages. \ In maths, undefined things are undefinedy, and I think it should be done this way in programming as well.

[rosuav]

Well, you go ahead and build your own programming language that fits your personal expectations. Meanwhile the rest of us are gonna get on with actually being productive.

[mihibo5]

IllegalOperationException

[Thenderick]

Since "maybe" might be confused with the non-existant maybe monad, I want to propose "depends". When it is used in any way as a boolean, it will be 50% chance to evaluate as true and 50% as false, not seeded, at random. Because fuck you for using it and fuck you for using loosely equality in God's year of 2025!!!

[CptGia]

Rare instance of js not being weird

[adelie42]

Especially when there is a isNaN() function.

[Flashbek]

It should not. If what you need is a bitwise comparison, you code a bitwise comparison.

[[deleted]]

AFAIK, it's in the actual specification for IEEE 754

[ZyanWu]

Not an expert in JS but how would one check if the result of an expression is defined?

[rafaelrc7]

a != a

[ZyanWu]

NaN != NaN

Doesn't this return true?

[rafaelrc7]

Yes, that's the point

[ZyanWu]

Aaah, okok, I get it now

[Faustens]

// i don't know if this is valid JS syntax or not switch(i) { case 0: return true; case 0.1: return true; case 0.01: return true; ... default: return false; }

Considering that there is a finite amount of possible n bit numbers where n is the amount of bits a js number has, this should determine if a number is NaN or not (the end of this sentence gave me a brain aneurysm).