On Sat, Jun 11, 2016 at 2:50 PM, Thorsten Seitz <tseit...@icloud.com> wrote:
> > > Am 10.06.2016 um 17:22 schrieb Erica Sadun via swift-evolution < > swift-evolution@swift.org>: > > > On Jun 10, 2016, at 8:02 AM, Xiaodi Wu via swift-evolution < > swift-evolution@swift.org> wrote: > > On Fri, Jun 10, 2016 at 7:18 AM, Haravikk <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. 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`. > > -Thorsten > > > private/StdlibUnittest/StdlibUnittest.swift.gyb: for j in > instances.indices where i != j { > public/core/Algorithm.swift: for value in rest where value < minValue { > public/core/Algorithm.swift: for value in rest where value >= maxValue { > > -- Erica > > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution > >
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