NaN and Infinity not allowed

[vallsv]

Hi,

While doing some tests, i found out that it is not possible to create quantities with NaN or Infinity.

I would like to know if it's an expected behavior.

import Qty from "js-quantities";

try {
  new Qty(Infinity, 'mm');
} catch (e) {
  console.log("Oupsi", e.message);
}

try {
  new Qty(NaN, 'mm');
} catch (e) {
  console.log("Oupsi...", e.message);
}

// Oupsi... Only number accepted as initialization value when units are explicitly provided

I am working on a system with python server. So i try to see if i can transpose everything on both sides.
For example, here is with Pint.

>>> import pint
>>> pint.Quantity(float('nan'), 'mm') / pint.Quantity(float('nan'), 's')
<Quantity(nan, 'millimeter / second')>

I was guessing javascript was already propagating NaN and Infinity properly inside js-quantities.
What do you think?

[vallsv]

BTW, if you like the idea, i can maybe try to do a PR. Tell me.

[glepretre]

I'm not sure to understand your use case? You would prefer to see NaN or Infinity rather than an error? 🤔

Even if it's not by design, I think it's better for js-quantities to refuse NaN or Inifinity as quantities scalar. These cases are more likely to be a bug rather than a feature for users.

[vallsv]

Exactly, i would like to have NaN and infinity, because that's float values like any others. Javascript already handle this cases with rules which are part of standards, that's the principle of least astonishment.

I am not really sure people are aware that operators could throw such exceptions, because it doesn't behave like javascript. But i understand your point. I am working on scientific software stack, i have to deal with such possibilities. But it's probably not a common use case.

BTW I did play a bit to see how it behave in some side corners. I was able to trick with unitless quantities. Maybe there is some cases you would like to fix anyway (tested with version 1.7.6).

  const big = new Qty(1e200);
  const inf = big.mul(big);
  console.log(`${inf}`);                  // this logs "Infinity"

  // console.log(`${zero.div(zero)}`);    // throw division by zero

  const nan = inf.sub(inf);
  console.log(`${nan}`);                  // this logs "NaN"

  const mm = new Qty(1e200, 'mm');
  const s = new Qty(1e200, 's');
  // console.log(`${mm.mul(s)}`);         // throw other.isTemperature is not a function