> Am 11.06.2016 um 23:52 schrieb Xiaodi Wu <[email protected]>: > >> On Sat, Jun 11, 2016 at 3:31 PM, Thorsten Seitz <[email protected]> wrote: >> >> >>> Am 11.06.2016 um 21:57 schrieb Xiaodi Wu <[email protected]>: >>> >>>> On Sat, Jun 11, 2016 at 2:50 PM, Thorsten Seitz <[email protected]> >>>> wrote: >>>> >>>> >>>>> Am 10.06.2016 um 17:22 schrieb Erica Sadun via swift-evolution >>>>> <[email protected]>: >>>>> >>>>> >>>>>> On Jun 10, 2016, at 8:02 AM, Xiaodi Wu via swift-evolution >>>>>> <[email protected]> wrote: >>>>>> >>>>>> On Fri, Jun 10, 2016 at 7:18 AM, Haravikk <[email protected]> >>>>>> wrote: >>>>>>>> * The word "where" does not consistently imply `break` or `continue`. >>>>>>>> In current Swift, `where` implies `break` in the context of a `while` >>>>>>>> loop and `continue` in the context of a `for` loop. Some users >>>>>>>> intuitively guess the correct meaning in each context, while others >>>>>>>> guess the wrong meaning. Therefore, the only way to learn for sure >>>>>>>> what `where` means in any context is to read the rulebook. That, by >>>>>>>> definition, means that this is unintuitive. >>>>>>> >>>>>>> This is an argument for renaming the where keyword on for loops to be >>>>>>> more clear, or to somehow integrate continue/break to be more explicit >>>>>>> about what the developer intends for it to do. >>>>>> >>>>>> Sure: I conclude that the keyword should be *either* removed *or* >>>>>> reformed; both outcomes could address the issue. >>>>> >>>>> This is my stance as well and I reserve the right to flit between both >>>>> choices until we've fully talked it through. >>>>> >>>>> One more data point. >>>>> >>>>> In the standard library there are just under 950 uses of "for in loops". >>>>> There are 3 uses of "for in while" : >>>> >>>> How many of the 950 "for in loops" use a guard with continue? Only these >>>> can be compard with the "for in where loops". >>> >>> That is a different argument, I think, from the one Erica is making. The >>> data you're asking about would answer the question, "How often do stdlib >>> authors prefer `guard` over `where`?" That is an interesting question, >>> certainly. >> >> It is the relevant question to ask when deciding whether `where` should be >> better replaced by `guard`. And it should be qualified by asking whether the >> respective author did know about `where`. I wouldn't want a language to be >> designed by looking at usage examples of inexperienced users... > > Here, I disagree with you vehemently. We should absolutely take into > consideration how inexperienced users work with the language. A language that > ignores the struggles and pain points of those who are less experienced is > one that will quickly find itself lacking in users.
You don't want to tell me in earnest that discovering and understanding `where` in for loops are stumbling blocks for beginners in a language containing generics, associated types, existentials, value vs. reference types etc.? -Thorsten >>> >>> I think Erica's point is that what Vladimir earlier called the "simple, >>> common" case may be simple but isn't actually common. I did a quick GitHub >>> search earlier today (and the tools aren't there, afaik, for an accurate >>> regexp search), but what I noticed on a random, not-statistically-sound >>> sampling was that uses of `continue` and `break`, when they do occur inside >>> a for loop (which isn't always), actually tend to happen after some work >>> has been done at the top of the loop. These wouldn't be replaceable by a >>> `where` clause. Moreover, I noticed an appreciable share of `return` and >>> `fatalError()` calls from inside the loop, which surprised me; I had >>> assumed I'd find mostly `break` or `continue`, but even when I did find >>> those it was as likely as not to be accompanied by logging. These again >>> preclude refactoring into `where`. >> >> Logging hints at logic used for filtering out data errors. That's a good >> usage for `guard` as opposed to `where`. The latter is about logic, not >> about error handling. >> >> -Thorsten >
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