On Tue, Apr 17, 2012 at 4:44 PM, Brendan Eich <bren...@mozilla.org> wrote:
> Brendan Eich wrote: > >> Irakli Gozalishvili wrote: >> >>> It would be amazing to have clojure like protocols in JS even without >>> `IFn`. I think it's very good feet and very useful in JS where each library >>> has it's own flavored API. I wrote more about it here: >>> http://jeditoolkit.com/2012/**03/21/protocol-based-** >>> polymorphism.html#post<http://jeditoolkit.com/2012/03/21/protocol-based-polymorphism.html#post> >>> >> >> Still hoping Mark will weigh in. >> > > Ok, I talked to Mark and Tom Van Cutsem, and they see no problem provided > we prevent overriding built-in [[Call]] and [[Construct]] on function > objects. > > Let there be private names @call and @construct (I'll spell them this way > to avoid tedious imports of const bindings from "@std" or another built-in > module). > > Let Clause 15.3.5 include new non-configurable, non-writable properties of > function objects named by @call and @construct (built-in functions have > only @call). The values are built-in and need a bit more thought than I can > spare now, but see below: @call's value is close to the original value of > Function.prototype.call, and @construct's value is straightforward enough I > think. > > Change 11.2.2 "The new Operator" to use @construct not [[Construct]], > passing the /argList// spread as actual positional parameters: (...argList). > > Change 11.2.3 "Function Calls" to use @call not [[Call]], passing the > /thisValue/ and /argList/ according to the Function.prototype.call > convention: (thisValue, ...argList). > > Change 11.4.3 "The typeof Operator", the table row with "Object (native or > host and does implement [[Call]])" in column 1, to test not for [[Call]] > and *not* for @call, rather to test [[NativeBrand]] === "Function" (see ES6 > draft 15.2.4.2 "Object.prototype.toString ( )"). > > This last point is important: we do not want an object's typeof-type to > change by giving it a @call property. But we do want to enable call and > construct protocols to be built by users, by giving objects @call and > @construct properties. > > This also simplifies direct proxies by allowing any proxy to have call and > construct traps. > > Comments welcome. What would happen if the object only defined one of these, but was used with the wrong one? Let's say I create an object Foo with @call, but not @construct, and then said new Foo()? Would it use @call and result in an error? What about vice versa? - Russ > > > /be > ______________________________**_________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/**listinfo/es-discuss<https://mail.mozilla.org/listinfo/es-discuss> >
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