es-discuss Digest, Vol 41, Issue 9

[Leo Meyerovich]

Is object identity the inverse of hash? So myObj == identity(hash(myObj))? Then weakly keyed or mapped tables are obviously possible, even though they'll have to be manually cleared of expired values.

Unfortunately, while this may support encoding weak mappings, I suspect a feature like that is used more often in frameworks than application code, so there might be a big penalty. ActionScript 3 introduced a Dictionary object that performs weak mappings -- perhaps that can be used to find a concrete comparison point. i don't know how this is distinct from 'ephemeron' tables, so I might be missing something.

- Leo



On Jul 3, 2010, at 12:00 PM, es-discuss-request at mozilla.org wrote:

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> Today's Topics:
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>   1. Re: We need to name "EphemeronTable" (was: Do we need an
>      experimental	extension naming convention?) (Brendan Eich)
>   2. Re: We need to name "EphemeronTable" (was: Do we need an
>      experimental	extension naming convention?) (P T Withington)
> 
> From: Brendan Eich <brendan at mozilla.com>
> Date: July 2, 2010 10:01:26 PM PDT
> To: Mark S. Miller <erights at google.com>
> Cc: "es-discuss at mozilla.org" <es-discuss at mozilla.org>, Erik Arvidsson <erik.arvidsson at gmail.com>
> Subject: Re: We need to name "EphemeronTable" (was: Do we need an experimental extension naming convention?)
> 
> 
> On Jul 2, 2010, at 7:45 PM, Mark S. Miller wrote:
> 
>> I'm also in favour of a regular Map and Set. Also a dense List (i.e., what we might have otherwise called an Array :(.) However, the history of oo class libraries shows collection libraries to be a tarpit, so I'm unwilling to take the lead on this issue. If someone else would like to, so long as they keep it bloody simple (i.e., not like Java, Smalltalk, or STL), that'd be great. Even the E collections <http://erights.org/elang/collect/tables.html> <http://erights.org/javadoc/org/erights/e/elib/tables/EMap.html>, where I could make them as simple as I wished, got way too complicated -- more complicated than I would find acceptable.
>> 
>> Great designers of extraordinarily simple expressive APIs, please step forward!
> 
> Ideally TC39 should not standardize or design anything not already proven and popular (if not dominant) in the field. The problem is no one can make practicaly O(1) collections without Object.hashcode and Object.identity.
> 
> Say we add hashcode and identity. Then we'll have to wait a while, Could we bootstrap Set, Map, and WeakMap and call it enough? I think so.
> 
> "Dense List" could be added but implementations are optimizing for dense arrays already. I think this one is too close to Array to be worth it, but without a detailed design that's just my gut reaction. FWIW.
> 
> /be
> 
> 
> 
> From: P T Withington <ptw at pobox.com>
> Date: July 3, 2010 4:47:50 AM PDT
> To: Brendan Eich <brendan at mozilla.com>
> Cc: "Mark S. Miller" <erights at google.com>, Erik Arvidsson <erik.arvidsson at gmail.com>, "es-discuss at mozilla.org" <es-discuss at mozilla.org>
> Subject: Re: We need to name "EphemeronTable" (was: Do we need an experimental extension naming convention?)
> 
> 
> Coming late to the party:  'alias' might be intuitive (from it's dictionary definition and use in filesystems as a non-preserving way to give an alternate name).
> 
> On 2010-07-03, at 00:57, Brendan Eich wrote:
> 
>> On Jul 2, 2010, at 8:58 PM, David Herman wrote:
>> 
>>>> Cool. I'm warming to WeakMap as well. Do we have any objections to WeakMap?
>>> 
>>> +1
>>> 
>>> I <3 WeakMap.
>> 
>> The Force is strong with WeakMap! ;-)
>> 
>> +1 or more
>> 
>> /be
>> 
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