operator overloading proposal

Isiah Meadows isiahmeadows at gmail.com
Tue May 10 15:25:32 UTC 2016


Here's my thought, if we go with syntax.

```js
class Point {
    // constructor, etc.

    operator +(other) {
        assert(other instanceof Point)
        return new Point(
            this.x + other.x,
            this.y + other.y)
    }

    operator +=(other) {
        assert(other instanceof Point)
        this.x += other.x
        this.y += other.y
    }
}
```

On Tue, May 10, 2016, 11:16 Brian Barnes <ggadwa at charter.net> wrote:

> A note on this from somebody who's entire existence seems dedicated to
> stopping as much stuff as possible from getting GC'd, the example below:
>
>  >const u = new Point(5, 10);
>  >const v = new Point(1, -2);
>  >
>  >const w = u + v;  // desugars to u[Symbol.add](v)
>  >console.log(w);   // { x: 6, y: 8 };
>
> Could += be a special case?  i.e.,
>
> u+=v;
>
> would call:
>
> Class Point { ... other stuff ...
> [whatever the syntax is](pt)
> {
> this.x+=pt.x;
> this.y+=pt.y;
> }
> }
>
> instead of desugaring to:
>
> u=u+v;          // which would cause the creation of an object and
>                 // leave the other to be collected
>
> For all I know, += might be doing such anyway in some engines, but for
> my stuff which is a lot of 3D math that could be a performance killer.
> It would be nice to be able to just add points and such, as long as the
> overhead is negligible.
>
> [>] Brian
>
> On 5/10/2016 10:52 AM, Isiah Meadows wrote:
> > I would prefer syntax + internal slots, since you'll know at creation
> > time whether the object has overloaded operators. It's much simpler for
> > the engine to figure out, and it's more performant because you only need
> > to check one thing instead of worrying about inheritance, own
> > properties, etc.
> >
> > Also, it would be IMHO easier to read than a symbol (the computed
> > property syntax is ugly IMO). Using a different concept than symbols
> > would also fit better with value types whenever any of those proposals
> > make it into the language (either the struct or special syntax).
> >
> >
> > On Tue, May 10, 2016, 04:03 G. Kay Lee
> > <balancetraveller+es-discuss at gmail.com
> > <mailto:balancetraveller%2Bes-discuss at gmail.com>> wrote:
> >
> >     Yes, I think exposing operators through well-known symbols is an
> >     interesting idea worthy of more exploration because it's precisely
> >     the purpose of well-known symbols to expose and allow manipulation
> >     to previously inaccessible internal language behaviors.
> >
> >     On Tue, May 10, 2016 at 1:59 PM, Kevin Barabash
> >     <kevinb at khanacademy.org <mailto:kevinb at khanacademy.org>> wrote:
> >
> >         > And remember that decorators are essentially just a syntax to
> >         apply functions to objects/classes at design time, so what
> >         you're proposing is essentially some new global function, which
> >         is going against the current trend and effort to better
> >         modularize/namespace all these utility functions/methods.
> >
> >         That's a really good point.
> >
> >         > It has been mentioned and discussed in numerous places over the
> >         years, you can find more info on this with some casual googling.
> >         For example:https://news.ycombinator.com/item?id=2983420
> >
> >         Thanks for the link.  I played around with sweet.js a bit over
> >         the weekend.  Using macros should work if we went with Python
> >         style operator overloading.  Instead of defining methods like
> >         _ADD_, _SUB_ etc. we could create some well-known symbols, maybe
> >         Symbol.plus, Symbol.times, etc.
> >
> >         ```
> >         class Point {
> >           constructor(x, y) {
> >             Object.assign(this, {x, y});
> >           }
> >
> >           [Symbol.add](other) {
> >             return new Point(this.x + other.x, this.y + other.y);
> >           }
> >         }
> >
> >         const u = new Point(5, 10);
> >         const v = new Point(1, -2);
> >
> >         const w = u + v;  // desugars to u[Symbol.add](v)
> >         console.log(w);   // { x: 6, y: 8 };
> >         ```
> >
> >         This would require default implementations to be defined on
> >         Object.prototype for Symbol.plus, Symbol.times, etc.
> >
> >
> >         On Sun, May 8, 2016 at 10:38 PM, G. Kay Lee
> >         <balancetraveller+es-discuss at gmail.com
> >         <mailto:balancetraveller+es-discuss at gmail.com>> wrote:
> >
> >             > Why not? The standard defines well-known symbols. Maybe
> `@operator` could be a well known decorator (assuming decorators get
> approved).
> >
> >             Well... you make something into the standard with proposals,
> >             not why-nots, so in order to make that happen you need to
> >             draft another proposal for well-known decorators. And
> >             remember that decorators are essentially just a syntax to
> >             apply functions to objects/classes at design time, so what
> >             you're proposing is essentially some new global function,
> >             which is going against the current trend and effort to
> >             better modularize/namespace all these utility
> >             functions/methods. And maybe a new mechanism could be
> >             drafted for these new well-known decorators, so that we can
> >             hide these new functions somewhere... but by now I hope it's
> >             becoming clear that it's introducing way too much new
> >             surface area for the language in exchange for one small
> feature.
> >
> >             > I haven't seen any proposals for macros, could you post a
> link?
> >
> >             It has been mentioned and discussed in numerous places over
> >             the years, you can find more info on this with some casual
> >             googling. For example:
> >             https://news.ycombinator.com/item?id=2983420
> >
> >
> >
> >             On Sun, May 8, 2016 at 2:51 PM, Kevin Barabash
> >             <kevinb at khanacademy.org <mailto:kevinb at khanacademy.org>>
> wrote:
> >
> >                 I should update the demo code to show the `@operator`
> >                 decorator in addition to `Function.defineOperator`.
> >
> >                 Initially I started out with just the `@operator`
> >                 decorator, but that meant that each class would have to
> >                 have knowledge of each of the classes it might want to
> >                 interact with before hand.  Having a separate
> >                 `defineOperator` function avoids this situation.
> >
> >                 It means that prototype style classes must be converted
> >                 to the new class syntax before operator overloading
> >                 could be used.  Lastly, there may be some cases where it
> >                 makes sense to overload operators with existing 3rd
> >                 party code or built-in classes, e.g. adding set
> >                 operations to Set using operator overloading.
> >
> >                 > It's also apparent that the `@operator decorator` part
> >                 of the proposal is an effort trying to address this
> >                 issue, but it really is not the responsibility of the
> >                 standard to try to define such a thing.
> >
> >                 Why not?  The standard defines well-known symbols.
> >                 Maybe `@operator` could be a well known decorator
> >                 (assuming decorators get approved).
> >
> >                 Slide 15
> >                 from http://www.slideshare.net/BrendanEich/js-resp shows
> >                 syntax for defining operators in value types which could
> >                 be adapted as follows for regular classes:
> >
> >                 ```
> >                 class Point {
> >                    constructor(x, y) {
> >                        this.x = +x;
> >                        this.y = +y;
> >                    }
> >                    Point + Number (a, b) {
> >                        return new Point(a.x + b, a.y + b);
> >                    }
> >                    Number + Point (a, b) {
> >                        return new Point(a + b.x, a + b.y);
> >                    }
> >                    Point + Point (a, b) {
> >                        return new Point(a.x + b.x, a.y + b.y);
> >                    }
> >                 }
> >                 ```
> >
> >                 Having to define `+` twice for `Point + Number` and
> >                 `Number + Point` seems like busy work, but maybe it's
> >                 better to be explicit.  What are you thoughts about this
> >                 syntax?
> >
> >                 > Another thing is that, IMHO, currently there are too
> >                 much quirks/conventions in the proposal that feel
> >                 non-evident and non-flexible which is destined to trip
> >                 people over from time to time. It would be great to make
> >                 a proposal that's simple and don't include too much
> >                 assumptions.
> >
> >                 Could you elaborator what quirks/conventions might trip
> >                 people up?
> >
> >                 > Finally, I'm not sure about the current status of
> >                 macros, but last I heard of it, they say it's going to
> >                 make its way into the standard pretty soon (TM), and
> >                 macros can do much of the things overloading could, and
> >                 much more.
> >
> >                 I haven't seen any proposals for macros, could you post
> >                 a link?
> >
> >
> >
> >
> >
> >
> >
> >                 On Sat, May 7, 2016 at 9:55 PM, G. Kay Lee
> >                 <balancetraveller+es-discuss at gmail.com
> >                 <mailto:balancetraveller+es-discuss at gmail.com>> wrote:
> >
> >                     I'd say it's way too early to ask for a champion on
> >                     this because just a quick skimming revealed a lot of
> >                     places that didn't add up. For example, the proposal
> >                     suggested that overloading is primarily targeted at
> >                     making it easier to work with user-defined classes,
> >                     but curiously a `Function.defineOperator()` method
> >                     is proposed instead of some syntax that feels more
> >                     tightly integrated with the class definition syntax.
> >
> >                     ```
> >
> >                     class Point {
> >                         constructor(x, y) {
> >                             Object.assign(this, { x, y });
> >                         }
> >
> >                         toString() {
> >                             return `(${this.x}, ${this.y})`;
> >                         }
> >                     }
> >
> >                     Function.defineOperator('+', [Point, Point], (a, b)
> => new Point(a.x + b.x, a.y + b.y));
> >
> >                     ```
> >
> >                     The demo code made this flaw evident - it looks like
> >                     a giant step backward to define an instance method
> >                     like this, don't you agree?
> >
> >                     It's also apparent that the `@operator decorator`
> >                     part of the proposal is an effort trying to address
> >                     this issue, but it really is not the responsibility
> >                     of the standard to try to define such a thing.
> >
> >                     What I'd suggest is that perhaps you should rethink
> >                     your proposed syntax and redesign it to become an
> >                     extension of the ES6 class definition syntax.
> >
> >                     Another thing is that, IMHO, currently there are too
> >                     much quirks/conventions in the proposal that feel
> >                     non-evident and non-flexible which is destined to
> >                     trip people over from time to time. It would be
> >                     great to make a proposal that's simple and don't
> >                     include too much assumptions.
> >
> >                     Finally, I'm not sure about the current status of
> >                     macros, but last I heard of it, they say it's going
> >                     to make its way into the standard pretty soon (TM),
> >                     and macros can do much of the things overloading
> >                     could, and much more.
> >
> >                     On Sun, May 8, 2016 at 8:51 AM, Kevin Barabash
> >                     <kevinb at khanacademy.org
> >                     <mailto:kevinb at khanacademy.org>> wrote:
> >
> >                         I forgot to mention in my last email that I'm
> >                         looking for a champion for this proposal.
> >
> >                         On Sat, May 7, 2016 at 5:24 PM, Kevin Barabash
> >                         <kevinb at khanacademy.org
> >                         <mailto:kevinb at khanacademy.org>> wrote:
> >
> >                             Hi everyone,
> >
> >                             I've been working on implementing operator
> >                             overloading and would like to submit a
> proposal.
> >
> >                             I think operator overloading would be a
> >                             useful addition to the language.  In
> >                             particular I think it would be useful for
> >                             defining operations on common mathematical
> >                             object types such as complex numbers,
> >                             vectors, matrices, and sets.
> >
> >                             I've create a working prototype that
> >                             consists of:
> >
> >                               * babel plugin that rewrites operators as
> >                                 function calls
> >                               * a polyfill which defines these functions
> >                                 and which call the correct
> >                                 argument-specific function based on the
> >                                 arguments' prototypes
> >                               * Function.defineOperator which can be
> >                                 used to define which function an
> >                                 operator should use for the specified
> types
> >                               * "use overloading" directive which allows
> >                                 users to opt-in
> >
> >                             More details can be found
> >                             at
> https://github.com/kevinbarabash/operator-overloading.
> >                             The babel plugin can be found
> >                             at
> https://github.com/kevinbarabash/babel-plugin-operator-overloading.
> >                             I also have a demo project at
> >
> https://github.com/kevinbarabash/operator-overloading-demo.
> >
> >                             The design was inspired by some of the
> >                             slides from
> >
> http://www.slideshare.net/BrendanEich/js-resp.
> >
> >                             – Kevin
> >
> >
> >
> >
> >                         _______________________________________________
> >                         es-discuss mailing list
> >                         es-discuss at mozilla.org
> >                         <mailto:es-discuss at mozilla.org>
> >                         https://mail.mozilla.org/listinfo/es-discuss
> >
> >
> >
> >                     _______________________________________________
> >                     es-discuss mailing list
> >                     es-discuss at mozilla.org <mailto:
> es-discuss at mozilla.org>
> >                     https://mail.mozilla.org/listinfo/es-discuss
> >
> >
> >
> >                 _______________________________________________
> >                 es-discuss mailing list
> >                 es-discuss at mozilla.org <mailto:es-discuss at mozilla.org>
> >                 https://mail.mozilla.org/listinfo/es-discuss
> >
> >
> >
> >             _______________________________________________
> >             es-discuss mailing list
> >             es-discuss at mozilla.org <mailto:es-discuss at mozilla.org>
> >             https://mail.mozilla.org/listinfo/es-discuss
> >
> >
> >
> >         _______________________________________________
> >         es-discuss mailing list
> >         es-discuss at mozilla.org <mailto:es-discuss at mozilla.org>
> >         https://mail.mozilla.org/listinfo/es-discuss
> >
> >
> >     _______________________________________________
> >     es-discuss mailing list
> >     es-discuss at mozilla.org <mailto:es-discuss at mozilla.org>
> >     https://mail.mozilla.org/listinfo/es-discuss
> >
> >
> >
> > _______________________________________________
> > es-discuss mailing list
> > es-discuss at mozilla.org
> > https://mail.mozilla.org/listinfo/es-discuss
> >
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20160510/70c1971a/attachment-0001.html>


More information about the es-discuss mailing list