# Proposal: 1) Number (integer or decimal) to Array 2) Array to Number (integer or decimal)

guest271314 guest271314 at gmail.com
Sun Mar 10 16:26:05 UTC 2019

```>
> (If you really wanted this as an integer, it's not well-founded; .567
> isn't exactly representable as a double, so JS doesn't know that you
> "meant" it to have only three digits after the decimal point, and thus
> want 567 as the answer. You'll instead get some very very large
> integer that *starts with* 567, followed by a bunch of zeros, followed
> by some randomish digits at the end.)

The code at the first post solves that problem.

But the question is still "what would someone use this information for?"

That question has been answered several times in the posts above. This
users' motivation was and is the ability to manipulate JavaScript
floating-point numbers  (which could be considered "broken", as you
described above) in order to solve mathematical problems (in this case,
directly calculating the *n*th lexicographic permutation) with the number
or decimal being represented as an array, without having to be concerned
with not getting the same value when the array is converted back to a
number.

Felipe Nascimento de Moura mentioned several other applications.

The work has already been done. This proposal is essentially to standardize
the naming conventions. Whether a Number method is used

i.getTensMethod

or an array is used

arr["integer"] // 1234

or an object where values are arrays is used

o["fraction"] // .567

Having mentioned Intl.NumberFormat earlier in the thread, if the issue
devoting resources to a *new *proposal, Intl.NumberFormate can be extended;
e.g. a rough draft in code

function formatNumberParts(args) {
return Object.assign({sign:0, fraction:[0], integer:[0]},
...args.filter(({type}) => type === "integer" || type === "fraction" ||
type === "minusSign").map(({type, value}) => ({[type === "minusSign" ?
"sign" : type]: type !== "minusSign" ? [...value].map(Number) : -1})));
}

let number = -123;

let formatter = new Intl.NumberFormat('en-US');

let res = formatter.formatToParts(number);

formatNumberParts(res);

If the concern is that the proposal would not be useful, consider what you
would *name* various uses of Math.trunc and remainder operator used at your
message?

On Sun, Mar 10, 2019 at 3:58 PM Tab Atkins Jr. <jackalmage at gmail.com> wrote:

> On Sat, Mar 9, 2019 at 11:10 AM Felipe Nascimento de Moura
> <felipenmoura at gmail.com> wrote:
> >
> > Personally, I don't think it would be THAT useful...
> > but...I think there is something behind this proposal that makes sense.
> >
> > I do believe it could be useful for developers to have an easier access
> to number parts or characteristics.
> > Perhaps something like:
> >
> > const i = 1234.567;
>
> Can you provide a scenario in which these would do something useful,
> such that it would be worth adding them over just using the math
> operations that already exist?
>
> > console.log( i.float ); // 567
>
> i % 1
>
> (If you really wanted this as an integer, it's not well-founded; .567
> isn't exactly representable as a double, so JS doesn't know that you
> "meant" it to have only three digits after the decimal point, and thus
> want 567 as the answer. You'll instead get some very very large
> integer that *starts with* 567, followed by a bunch of zeros, followed
> by some randomish digits at the end.)
>
> > console.log( i.abs ); // 1234
>
> Math.trunc(i)
>
> > console.log( i.thousands ); // 1
>
> Math.trunc(i / 1000)
>
> > console.log( i.million ); // 0
>
> Math.trunc(i / 1e6)
>
> > console.log( i.hundred ); // 2
>
> Math.trunc(i / 100) % 10
>
> > console.log( i.hundreds ); // 12
>
> Math.trunc(i / 100)
>
> > console.log( i.ten ); // 2
>
> Math.trunc(i / 10) % 10
>
> > console.log( i.tens ); // 123
>
> Math.trunc(i / 10)
>
> > console.log( i.tenth ); // 5
>
> Math.trunc(i % 1 * 10) % 10
>
> > console.log( i.tenths ); // 5
>
> Math.trunc(i % 1 * 10)
>
> > console.log( i.hundredth ); // 6
>
> Math.trunc(i % 1 * 100) % 10
>
> > console.log( i.hundredths ); // 56
>
> Math.trunc(i % 1 * 100)
>
>
> Some of these are easy to remember and use; others take some thinking
> to deploy. But the question is still "what would someone use this
> information for?", such that the benefit to developers is worth the
> cost to all parties involved (spec writers, implementors, testers, and
> then developers having to navigate a larger stdlib).
>
> ~TJ
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
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