introduction. It's also part of why I want an operator - this is one

of the few times where spreading FUD *is* a good idea IMHO.

>

> Code that uses % is often surprisingly buggy. For example even a simple function such as this is broken if n is negative:

>

> function isOdd(n) {

> return n % 2 === 1;

> }

>

> isOdd(-3) // false

>

> The same is not true in other programming languages. The same in Python works just fine:

>

> def isOdd(n):

> return n % 2 == 1

>

> isOdd(-3) // true

>

> The advantage of an operator over a function is that it allows us to say to people who are new to JS: "Always use %% instead of % unless you have a good reason". Just the same as we say "Always use === instead of == unless you have a good reason".

>

>

> On Thu, Aug 15, 2019 at 10:01 PM Isiah Meadows <

[hidden email]> wrote:

>>

>> BTW, I just wrote up a more precise, formalized proposal over here:

>>

https://github.com/isiahmeadows/proposal-divisor-dependent-modulo/,

>> and I'd be more than willing to work with a TC39 champion on it. I

>> personally prefer syntax (pretty strongly), but I'm not beholden to

>> it.

>>

>> I do feel the semantics are simple enough it'd be okay to lower it to

>> syntax, and it naturally just glides right in. I find it *very* odd

>> that some languages use a simple operator `%` or relatively short

>> function for remainder keeping the sign of the dividend but relegate

>> the version keeping the sign of the divisor (the more useful and

>> intuitive of them) to a much more verbose function call. Of all

>> Wikipedia lists in

https://en.wikipedia.org/wiki/Modulo_operation,

>> here's the four that do this currently - all but one expose an

>> operator for the first:

>>

>> - Fortran: `mod` for dividend-dependent, `modulo` for divisor-dependent

>> - Julia: `%`/`rem` for dividend-dependent, `mod` for divisor-dependent

>> - Java: `%` for dividend-dependent, `Math.floorMod` for divisor-dependent

>> - XBase++: `%` for dividend-dependent, `Mod` for divisor-dependent

>>

>> And it's worth noting most other languages (including some end

>> user-oriented ones) that show a syntactic preference to one or the

>> other expose a simpler one where the sign matches the divisor, a more

>> complicated one where the sign matches the dividend. For a variety of

>> examples:

>>

>> - Ruby: `%`/`modulo` for divisor-dependent, `remainder` for dividend-dependent

>> - SML: `mod` for divisor-dependent, `Int.rem` for dividend-dependent

>> - Elm: `modBy` for divisor-dependent, `remainderBy` for dividend-dependent

>> - Euphoria: `mod` for divisor-dependent, `remainder` for dividend-dependent

>> - Python: `%` for divisor-dependent, `math.fmod` for dividend-dependent

>> - Smalltalk: `\\` for divisor-dependent, `rem:` for dividend-dependent

>>

>> And of course, many don't even expose a type of modulo where the sign

>> matches the divisor. For some examples:

>>

>> - APL

>> - LibreOffice/Excel

>> - Lua

>> - Perl

>> - Mathematica

>> - PL/I

>> - TCL

>>

>> There's also Dart, a relatively new language which defaults to

>> non-negative always.

>>

>> This relatively long list of languages, *despite* C's heritage and

>> semantics being inherited in much of them, makes me question using a

>> function for this, and there would need to be a *lot* of FUD to get

>> people to use the function more than the operator.

>>

>> So this is why I would prefer an operator as opposed to syntax for this.

>>

>> -----

>>

>> Isiah Meadows

>>

[hidden email]
>> www.isiahmeadows.com

>>

>> On Thu, Aug 15, 2019 at 3:58 PM Jordan Harband <

[hidden email]> wrote:

>> >

>> > Static functions don't have the same risk as prototype functions; `Math.mod` would make sense to add.

>> >

>> > One suggestion, though, would be to try to add the API method first, and look at usage for awhile before trying to add the syntax.

>> >

>> > On Thu, Aug 15, 2019 at 10:12 AM Andrea Giammarchi <

[hidden email]> wrote:

>> >>

>> >> To me there's no risk, as MooTools, Prototype, and Scriptacolous are both things of the past, and never implemented Math.mod ... so, with that approach, custom transpiling functions are more dangerous, as somebody might have implemented `%%` already for other purposes, and we break Babel outcome adding new syntax anyway ... the smoosh accident, is the equivalent of custom Babel utilities these days.

>> >>

>> >> Look at TypeScript and the private class fields, if you want to compare new syntax instead

>> >>

>> >> On Thu, Aug 15, 2019 at 4:50 PM Michael Haufe <

[hidden email]> wrote:

>> >>>

>> >>> Thursday, August 15, 2019 2:47 AM, Andrea Giammarchi wrote:

>> >>>

>> >>>

>> >>>

>> >>> > FWIW another disadvantage is that operators cannot be polyfilled, so it'll take forever for those not using transpilers to adopt these, while having a `Math,mod` would work right away

>> >>>

>> >>>

>> >>>

>> >>>

>> >>>

>> >>> With such an approach there is risk of another ‘smooshgate’ [1][2]. There is nothing stopping those developers from using a function anyway to bridge the gap if they can’t or won’t use a compiler. This is already the current state of affairs.

>> >>>

>> >>>

>> >>>

>> >>> [1]

https://developers.google.com/web/updates/2018/03/smooshgate>> >>>

>> >>> [2]

https://adamsilver.io/articles/the-disadvantages-of-javascript-polyfills/>> >>>

>> >>>

>> >>>

>> >>> Michael

>> >>

>> >> _______________________________________________

>> >> es-discuss mailing list

>> >>

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>> >>

https://mail.mozilla.org/listinfo/es-discuss>> >

>> > _______________________________________________

>> > es-discuss mailing list

>> >

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>> >

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