StopIteration, ForwardToTarget, ... & symbols
brendan at mozilla.org
Mon Nov 26 17:27:27 PST 2012
David Bruant wrote:
> Le 26/11/2012 22:11, Brendan Eich a écrit :
>> Herby Vojčík wrote:
>>> shouldn't StopIteration, ForwardToTarget from "Notification proxies"
>>> thread and similar ones be rather well-known unique symbols (like
>>> @iterator), now that we have them, instead of well-known globals? \
>> Let's separate the naming and unique identity concerns. Objects have
>> unique identity, so do symbols. But if a unique identity is required
>> without being a property key, then an object is the right answer, not
>> a symbol.
> I'm not sure not being a property key is that big of a constraint, so
> I would say that objects and symbols are both valid equally valid.
Perhaps not, but it's odd to make a symbol just for (e.g.) immutability
with no properties or [[Prototype]]. For realm-independence is more
interesting. More below, on your good point I had forgotten momentarily
in replying to Allen a minute ago.
>> I think this applies to StopIteration.
> It is suggested on the strawman that StopIteration be a constructor
>  and I support this idea for StopIteration because an iterator may
> have different reasons to stop and building instances with a message
> (or any property) attached.
Yes, indeed, and StopIteration as constructor is used implicitly when a
generator function returns a value. This makes the case for object not
symbol. isStopIteration copes with realm-dependence.
> I'm not sure It'd be as relevant for ForwardToTarget.
I leave that to you and Tom :-P.
>  http://wiki.ecmascript.org/doku.php?id=harmony:iterators
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