3 ms·

Maybe the result of NaN === NaN should be neither true nor false but NaB (not a bool).

by ema 11mo ago

disgruntledphd2 11mo ago
In R, NA (which is almost, but not quite like NaN) actually has separate types for each result, so you can have NA_boolean, NA_integer etc. Its super confusing.
- getnormality 11mo ago
  It is a minor nuisance, but I think there's ultimately a pretty good reason for it. Old-school base R is less type-sensitive and more "do what I mean", but that leads to slowness and bugs. Now we have the tidyverse, which among many other things provides a new generation of much faster functions with vectorized C implementations under the hood, but this requires them to be more rigid and type-sensitive. When I want to stick a NA into one of these, I often have to give it the right type of NA, or it'll default to NA_boolean and I'll get type errors.
  - disgruntledphd2 11mo ago
    > When I want to stick a NA into one of these, I often have to give it the right type of NA, or it'll default to NA_boolean and I'll get type errors. Yeah, I know. I hit this when I was building S4 classes, which are similarly type-strict. Again, I think this was the right decision (pandas's decision was definitely not), but it was pretty confusing the first time.
monkpit 11mo ago
NaN is, by definition, not equal to NaN because they’re not comparable, it does have a definitive Boolean representation - false is correct
- deleted 11mo ago
  [deleted]
zahlman 11mo ago
The concept of NaN long predates the language that uses ===, and is part of a language-agnostic standard that doesn't consider other data types. Any language choosing to treat the equality (regardless of the operator symbol) of NaN differently would be deviating from the spec.
- freehorse 11mo ago
  Julia evaluates NaN === NaN to true, as long as the underlying bit representations are the same. Eg NaN === -NaN evaluates to false, as happens also with NaNs where for some reason you tinker with their bytes. I think it makes sense that it is so though, regardless that I cannot think of any actual use cases out of doing weird stuff.
steveBK123 11mo ago
Typed nulls are good
charcircuit 11mo ago
Or a 3rd option is it should not be allowed similar to dividing by 0.
- freehorse 11mo ago
  What do you mean "not allowed"? Throwing a compile or runtime error? Many languages allow division by zero, and x/0 typically gives inf unless x is 0, then x/0 gives nan. If x is negative then x/0 gives -inf. Of course this all can get tricky with floats, but mathematically it makes sense to divide by zero (interpreted as a limit). For NaNs, maybe in some domains it could make sense, but eg I would find it impractical when wanting to select rows based on values in a column and stuff like that.
sophrosyne42 11mo ago
It should throw a compile-time error. Anything like this which allows an invalid or unmeaningful operation to evaluate at compile-time is rife for carrying uncaught errors at run-time.
freehorse 11mo ago
What would an `if (NaB) ... else ...` block do? Either you throw an exception (and imo it is better to just throw an exception before that already, then) or else what you do determines what NaN === NaN actually evaluates to.
- lioeters 11mo ago
  Apparently NaN (not a number) becomes false when type-cast to boolean. Boolean(NaN) ===> false For a hypothetical NaB (not a boolean), the same behavior seems logical. Boolean(NaB) ===> false So the condition `if (NaB)` is false and will fall through to the `else` branch. But.. > what you do determines what NaN === NaN actually evaluates to I think I disagree with this because it's not about casting to boolean, it's a totally different question of self-identity, or comparing two instances (?) of a value (?!). From the article: typeof NaN ===> "number" For symmetry and consistency: typeof NaB ===> "boolean" > NaN is the only value in the whole of JavaScript that isn’t equal to itself .. the concept of NaN is meant to represent a breakdown of calculation Similarly, NaB would represent a breakdown of true/false condition (somehow) as an exceptional case. Whether it equals itself is a matter of convention or language design, not logic - since it's beyond logic just as NaN is beyond numbers. I would say: NaN === NaN ===> false NaB === NaB ===> false > you throw an exception (and imo it is better.. I agree throwing an exception is better design for such exceptional cases - but we know JavaScript as a cowboy language would rather plow through such ambiguities with idiosyncratic dynamic typing, and let the user figure out the implicit logic (if any).
  - freehorse 11mo ago
    I don't necessarily think about JS in particular. A lot of languages have similar design and prob most have to deal with this issue in general. In your examples, it does not make sense to have both typeof NaB ===> "boolean" and Boolean(NaB) ===> false But maybe if you had NaB it would make sense to evaluate Boolean(NaN) ===> NaB And maybe also evaluate `NaN === 1` to NaB? I am not too fond of NaB because boolean is supposed to encode binary logic. There exists ternary logic and other concepts that could be used if you do not want strictly two values. Or if you want to encode exceptional values, no reason not to use int8 directly, instead of calling it boolean but actually using sth that could be represented as int8 (NaB has to be represented by some byte anwyay). In general, tbh, I think often it is not useful to encode your logic with booleans because many times you will need to encode exceptional values one way or another. But NaB will not solve that, as it will just function as another way to encode false at best, throwing exceptions around at worst. > Similarly, NaB would represent a breakdown of true/false condition (somehow) as an exceptional case. Still, in JS `NaN || true` evaluates to `true` hence I assume `NaB || true` should evaluate to true too. It is not quite the same as NaN + 1 evaluating to NaN. And as NaN (and hence NaB) functions as false when logical operations are involved for all intents and purposes, except if you exactly inquire for it with some isNaB() or sth, to me NaB is another way to encode false, which is probably fine depending what you want it for.

Maybe the result of NaN === NaN should be neither true nor false but NaB (not a bool).

by ema 11mo ago

Maybe the result of NaN === NaN should be neither true nor false but NaB (not a bool).

In R, NA (which is almost, but not quite like NaN) actually has separate types for each result, so you can have NA_boolean, NA_integer etc. Its super confusing.

getnormality 11mo ago
It is a minor nuisance, but I think there's ultimately a pretty good reason for it. Old-school base R is less type-sensitive and more "do what I mean", but that leads to slowness and bugs. Now we have the tidyverse, which among many other things provides a new generation of much faster functions with vectorized C implementations under the hood, but this requires them to be more rigid and type-sensitive. When I want to stick a NA into one of these, I often have to give it the right type of NA, or it'll default to NA_boolean and I'll get type errors.
- disgruntledphd2 11mo ago
  > When I want to stick a NA into one of these, I often have to give it the right type of NA, or it'll default to NA_boolean and I'll get type errors. Yeah, I know. I hit this when I was building S4 classes, which are similarly type-strict. Again, I think this was the right decision (pandas's decision was definitely not), but it was pretty confusing the first time.

monkpit 11mo ago

NaN is, by definition, not equal to NaN because they’re not comparable, it does have a definitive Boolean representation - false is correct

deleted 11mo ago
[deleted]

zahlman 11mo ago

The concept of NaN long predates the language that uses ===, and is part of a language-agnostic standard that doesn't consider other data types. Any language choosing to treat the equality (regardless of the operator symbol) of NaN differently would be deviating from the spec.

freehorse 11mo ago
Julia evaluates NaN === NaN to true, as long as the underlying bit representations are the same. Eg NaN === -NaN evaluates to false, as happens also with NaNs where for some reason you tinker with their bytes. I think it makes sense that it is so though, regardless that I cannot think of any actual use cases out of doing weird stuff.

steveBK123 11mo ago

Typed nulls are good

charcircuit 11mo ago

Or a 3rd option is it should not be allowed similar to dividing by 0.

freehorse 11mo ago
What do you mean "not allowed"? Throwing a compile or runtime error? Many languages allow division by zero, and x/0 typically gives inf unless x is 0, then x/0 gives nan. If x is negative then x/0 gives -inf. Of course this all can get tricky with floats, but mathematically it makes sense to divide by zero (interpreted as a limit). For NaNs, maybe in some domains it could make sense, but eg I would find it impractical when wanting to select rows based on values in a column and stuff like that.

sophrosyne42 11mo ago

It should throw a compile-time error. Anything like this which allows an invalid or unmeaningful operation to evaluate at compile-time is rife for carrying uncaught errors at run-time.

freehorse 11mo ago

What would an `if (NaB) ... else ...` block do? Either you throw an exception (and imo it is better to just throw an exception before that already, then) or else what you do determines what NaN === NaN actually evaluates to.

lioeters 11mo ago
Apparently NaN (not a number) becomes false when type-cast to boolean. Boolean(NaN) ===> false For a hypothetical NaB (not a boolean), the same behavior seems logical. Boolean(NaB) ===> false So the condition `if (NaB)` is false and will fall through to the `else` branch. But.. > what you do determines what NaN === NaN actually evaluates to I think I disagree with this because it's not about casting to boolean, it's a totally different question of self-identity, or comparing two instances (?) of a value (?!). From the article: typeof NaN ===> "number" For symmetry and consistency: typeof NaB ===> "boolean" > NaN is the only value in the whole of JavaScript that isn’t equal to itself .. the concept of NaN is meant to represent a breakdown of calculation Similarly, NaB would represent a breakdown of true/false condition (somehow) as an exceptional case. Whether it equals itself is a matter of convention or language design, not logic - since it's beyond logic just as NaN is beyond numbers. I would say: NaN === NaN ===> false NaB === NaB ===> false > you throw an exception (and imo it is better.. I agree throwing an exception is better design for such exceptional cases - but we know JavaScript as a cowboy language would rather plow through such ambiguities with idiosyncratic dynamic typing, and let the user figure out the implicit logic (if any).
- freehorse 11mo ago
  I don't necessarily think about JS in particular. A lot of languages have similar design and prob most have to deal with this issue in general. In your examples, it does not make sense to have both typeof NaB ===> "boolean" and Boolean(NaB) ===> false But maybe if you had NaB it would make sense to evaluate Boolean(NaN) ===> NaB And maybe also evaluate `NaN === 1` to NaB? I am not too fond of NaB because boolean is supposed to encode binary logic. There exists ternary logic and other concepts that could be used if you do not want strictly two values. Or if you want to encode exceptional values, no reason not to use int8 directly, instead of calling it boolean but actually using sth that could be represented as int8 (NaB has to be represented by some byte anwyay). In general, tbh, I think often it is not useful to encode your logic with booleans because many times you will need to encode exceptional values one way or another. But NaB will not solve that, as it will just function as another way to encode false at best, throwing exceptions around at worst. > Similarly, NaB would represent a breakdown of true/false condition (somehow) as an exceptional case. Still, in JS `NaN || true` evaluates to `true` hence I assume `NaB || true` should evaluate to true too. It is not quite the same as NaN + 1 evaluating to NaN. And as NaN (and hence NaB) functions as false when logical operations are involved for all intents and purposes, except if you exactly inquire for it with some isNaB() or sth, to me NaB is another way to encode false, which is probably fine depending what you want it for.