unknownPrivateSymbol trap (was: WeakMap better than Private Symbols? (was: direct_proxies "problem"))

Herby Vojčík herby at mailbox.sk
Tue Jan 15 13:43:35 PST 2013



Tom Van Cutsem wrote:
> 2013/1/15 Herby Vojčík <herby at mailbox.sk <mailto:herby at mailbox.sk>>
>
>     Is it needed? Maybe the "fail/forward" decision canbe set
>     beforehand, when creating the proxy. Then, no trap will be called
>     (but you cannot change the response in time; OTOH, is there a use
>     case for it?).
>
>     Or does it do something more sophisticated then just telling
>     "forward" or "fail" for situation that I am accessing some unknown
>     private symbol?
>
>
> Here's one example where the decision would need to be dynamic: a
> revocable reference (not a membrane) that wants to just forward all
> operations to the target until revoked. When revoked, it does not want
> to forward anything anymore, including private symbol accesses.

These use cases can be made dynamic be some kind of

   Proxy.fromNowOnForwardUnknownPrivateSymbols(proxy, false);

API. This is not truly dynamic. I'd say no truly dynamic use cases 
exist, where you must decide _at_the_exact_point_of_access_. IMO.

>
> That said, if this is not an important use case, I'm open to making the
> decision static. I'm not too fond of the "unknownPrivateSymbol" trap.
>
> Cheers,
> Tom

Herby


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