<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">Am 12.06.2016 um 00:16 schrieb Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" class="">xiaodi.wu@gmail.com</a>>:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote">On Sat, Jun 11, 2016 at 5:07 PM, Thorsten Seitz <span dir="ltr" class=""><<a href="mailto:tseitz42@icloud.com" target="_blank" class="">tseitz42@icloud.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto" class=""><div class=""></div><div class=""><br class=""></div><div class=""><br class="">Am 11.06.2016 um 23:52 schrieb Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank" class="">xiaodi.wu@gmail.com</a>>:<br class=""><br class=""></div><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote">On Sat, Jun 11, 2016 at 3:31 PM, Thorsten Seitz <span dir="ltr" class=""><<a href="mailto:tseitz42@icloud.com" target="_blank" class="">tseitz42@icloud.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto" class=""><span class=""><div class=""></div><div class=""><br class=""></div><div class=""><br class="">Am 11.06.2016 um 21:57 schrieb Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank" class="">xiaodi.wu@gmail.com</a>>:<br class=""><br class=""></div><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote">On Sat, Jun 11, 2016 at 2:50 PM, Thorsten Seitz <span dir="ltr" class=""><<a href="mailto:tseitz42@icloud.com" target="_blank" class="">tseitz42@icloud.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto" class=""><span class=""><div class=""></div><div class=""><br class=""></div><div class=""><br class="">Am 10.06.2016 um 17:22 schrieb Erica Sadun via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>>:<br class=""><br class=""></div><blockquote type="cite" class=""><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jun 10, 2016, at 8:02 AM, Xiaodi Wu via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>> wrote:</div><br class=""><div class=""><div dir="ltr" class="">On Fri, Jun 10, 2016 at 7:18 AM, Haravikk <span dir="ltr" class=""><<a href="mailto:swift-evolution@haravikk.me" target="_blank" class="">swift-evolution@haravikk.me</a>></span> wrote:<br class=""><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class=""><div class=""><span class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px" class=""><div class="gmail_extra"><div class="gmail_quote"><div class="">* 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.</div></div></div></div></div></blockquote><div class=""><br class=""></div></span><div class="">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.</div></div></div></blockquote><div class=""><br class=""></div><div class="">Sure: I conclude that the keyword should be *either* removed *or* reformed; both outcomes could address the issue.</div></div></div></div></div></blockquote><div class=""><br class=""></div>This is my stance as well and I reserve the right to flit between both choices until we've fully talked it through.</div><div class=""><br class=""></div><div class="">One more data point. </div><div class=""><br class=""></div><div class="">In the standard library there are just under 950 uses of "for in loops". There are 3 uses of "for in while" :</div></div></blockquote><div class=""><br class=""></div></span>How many of the 950 "for in loops" use a guard with continue? Only these can be compard with the "for in where loops".</div></blockquote><div class=""><br class=""></div><div class="">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.</div></div></div></div></div></blockquote><div class=""><br class=""></div></span>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...<div class=""><span class=""><br class=""></span></div></div></blockquote><div class=""><br class=""></div><div class="">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.</div></div></div></div></div></blockquote><div class=""><br class=""></div><div class="">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.?</div></div></blockquote><div class=""><br class=""></div><div class="">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`).</div></div></div></div></div></blockquote><div><br class=""></div>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.</div><div><br class=""></div><div>-Thorsten</div><div><br class=""></div><div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto" class=""><div class=""><br class=""></div><div class="">-Thorsten </div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto" class=""><div class=""><span class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""><br class=""></div><div class="">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`.</div></div></div></div></div></blockquote><div class=""><br class=""></div></span>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. </div><span class=""><font color="#888888" class=""><div class=""><br class=""></div><div class="">-Thorsten <br class=""></div></font></span></div></blockquote></div><br class=""></div></div>
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