> Am 12.06.2016 um 00:16 schrieb Xiaodi Wu <xiaodi...@gmail.com>: > > On Sat, Jun 11, 2016 at 5:07 PM, Thorsten Seitz <tseit...@icloud.com > <mailto:tseit...@icloud.com>> wrote: > > > Am 11.06.2016 um 23:52 schrieb Xiaodi Wu <xiaodi...@gmail.com > <mailto:xiaodi...@gmail.com>>: > >> On Sat, Jun 11, 2016 at 3:31 PM, Thorsten Seitz <tseit...@icloud.com >> <mailto:tseit...@icloud.com>> wrote: >> >> >> Am 11.06.2016 um 21:57 schrieb Xiaodi Wu <xiaodi...@gmail.com >> <mailto:xiaodi...@gmail.com>>: >> >>> On Sat, Jun 11, 2016 at 2:50 PM, Thorsten Seitz <tseit...@icloud.com >>> <mailto:tseit...@icloud.com>> wrote: >>> >>> >>> Am 10.06.2016 um 17:22 schrieb Erica Sadun via swift-evolution >>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>>: >>> >>>> >>>>> On Jun 10, 2016, at 8:02 AM, Xiaodi Wu via swift-evolution >>>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >>>>> >>>>> On Fri, Jun 10, 2016 at 7:18 AM, Haravikk <swift-evolut...@haravikk.me >>>>> <mailto:swift-evolut...@haravikk.me>> 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.? > > I do. I challenge you to find an introductory text that teaches generics, > associated types, existentials, or even value vs. reference types before it > introduces `for` loops or `if` (and `guard`).
My point was that someone who endeavors to learn a language like Swift which does include all these things, will not falter when he stumbles upon `where` in a `for` loop. He might be surprised for a moment (when coming from other languages but probably not when Swift is his first language, nor when he already knows languages like C# or SQL) but not more. -Thorsten > > > -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 >> >
_______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
