> On Oct 3, 2016, at 10:54 PM, Tab Atkins Jr. <jackalm...@gmail.com> wrote: > >> On Sun, Oct 2, 2016 at 2:11 AM, Caitlin Potter <caitpotte...@gmail.com> >> wrote: >>> On Oct 2, 2016, at 10:50 AM, Awal Garg <awalg...@gmail.com> wrote: >>>> On Oct 2, 2016, at 9:30 AM, Olivier Lalonde <olalo...@gmail.com> wrote: >>>> So what's the problem with `[...a, last]` that `[...a]` doesn't have? I >>>> still don't get it. >>> >>> Since you don’t know when the iterator produced for `…a` will terminate, >>> there’s no way to know when you need to stop iterating `…a` and move onto >>> the next item `last`. >> >> That statement is factually incorrect. There is a simple criteria to know >> when to terminate the iteration for a final rest element, which is when the >> iterator returns a result object with "done": true. >> >> There is no condition to determine when to switch from a non-final rest >> element to some other element. That is a problem which needs to be >> addressed. > > I'm similarly confused - there's no need to "determine when to > switch"; we don't evaluate things in different contexts or anything. > It just requires storage equal to the number of post-rest arguments; > when you do hit the end, the things you're holding onto get assigned > to the post-rest variable names. This is all done internally with a > freshly-produced array; I don't *think* the timing of array-appending > is even observable, so you shouldn't be able to tell that an item is > appended only after later items are pulled from the source iterator. > > I'm similarly confused by the wording you're using, tho, which > suggests there may be a deeper communication mismatch - there's no > "iterator produced for `...a`". The ...a just indicates that you need > to pull on the iterator being assigned to the destructuring pattern, > and store the results that aren't claimed by other parts of the > destructuring pattern into "a". > > ~TJ
"I'm similarly confused about your assertion that this idea needs to avoid a halting problem, because here's a way around this problem, not suggested by anyone else, with a non-negligible cost, so there"? Really? I'm asking how they would alter IteratorBindingInitialization. It's not rocket science, but it's important for the discussion. _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
