+1, especially on the last point. As something added to iterators rather than iterables in ES6, there's no reason for "return" to be a symbol rather than a string.
On Sat, Apr 26, 2014 at 9:59 AM, Brendan Eich <[email protected]> wrote: > Kevin Smith wrote: > >> >> >> In this case we have try-finally statements as an existing >> feature. The semantics of this feature is a bounded execution >> scope with a cleanup action on completion. This feature is widely >> used and has always been internally consistent and reliable, >> expect for catastrophic external failure or intervention (ie, >> externally imposed process termination, power failure, etc). >> People use it for all sorts of things, including bounded resource >> management. >> >> >> Zeroing in on "cleanup action on completion": don't co-routines by >> nature prohibit us from reasoning in this way about completion? It seems >> to me that this shift is broader than just `try/finally`, although I agree >> that `try/finally` shows some particularly acute symptoms. >> >> And I also agree that we should not provide gratuitous footguns. >> Unfortunately, though, I'm having a hard time forming an opinion on how >> disallowing `try/yield/finally` would balance out. >> > > We're at risk of going around the design wheel again. > > Python started by banning yield in try: and then added it, with > GeneratorExit as a magic exception thrown from Python's implicitly-called > generator.close method at a yield-in-try that would run the finally clauses. > > When Igor Bukanov and I were working on ES4 and prototyping it in > SpiderMonkey, Igor urged forcing a return instead of throwing a magic > exception. He even persuaded Philip J. Eby on python-dev that forcing > return was better, possibly even for Python (which IIRC then went in the > direction of reifying control effects as exceptions). > > Instead of kicking the can and dragging this out yet again, I'm ok with > return automation as proposed. Yeah, we're doing a common-ish use-case > affordance. No, it isn't the last case where scoped resource release will > come up. But yes, it has precedent in other languages and it's useful. > > BTW Dave Herman persuaded me we don't need to use a symbol for the name; > 'return' is ok if 'next' is. The iteration protocol hooks via @@iterator, > which returns an instance of something coded new implementations, so > implementors can avoid using 'return' for a different purpose without > conflict. IOW, one symbol-name is enough! > > /be > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > -- Cheers, --MarkM
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