On Tue, Jan 22, 2013 at 2:47 AM, Jason Orendorff
<jason.orendo...@gmail.com> wrote:
> On Mon, Jan 21, 2013 at 6:04 AM, David Bruant <bruan...@gmail.com> wrote:
>>
>> [...] WeakMap.prototype.clear questions the property that was true before
>> its adoption ("you can only modify a weakmap entry if you have the key")
>
>
> David, would you please elaborate your argument for this invariant? This the
> first I've seen it stated.
>
> An invariant can be a powerful thing. Still, I guess my default position is
> that (1) the object-capabilities perspective is only one view among many;Of course. > (2) even looking at things with an eye for o-c integrity and security, > clearing a data structure seems like a reasonable thing to allow, treating a > reference to the data structure itself as a sufficient capability. It's (2) > that I would especially like you to address. In general, yes. Maps exist as simply a useful mutable container data structure. .clear is perfectly reasonable to allow on maps, and indeed neither I nor anyone I recall has raised any objections to this. But WeakMaps were introduced specifically to support rights amplification[1]. Because of this special need for WeakMaps, we introduced them first. The Maps and Set strawmen came later. Since the get/set/has/delete functionality of WeakMaps and Maps seem naturally related, we proceeded considering them to be related -- both by name of the abstraction and by compatibility of their common methods. This still seems attractive to me. But this type-like relationship between them seems to be causing more confusion than clarity. Their purposes are very different. [1] <http://www.youtube.com/watch?v=oBqeDYETXME> has a good explanation of rights amplification, and shows the purse example as an example. > > Cheers, > -j > > > _______________________________________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/listinfo/es-discuss > -- Cheers, --MarkM _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
