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. > > 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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