<div dir="ltr">Hopefully this is still the right place to discuss this proposal (it's <a href="https://github.com/apple/swift-evolution/blob/master/schedule.md" target="_blank">listed as being in active review</a>, but I don't see a separate [Review] thread).<div><br></div><div>I like this proposal. I think it will bring some much-needed ease-of-use.</div><div><br></div><div>I'm not sold on the "..." placeholder for the memberwise arguments, though. I know this was suggested by Chris Lattner, so I'm tempted to defer to his judgement. But here are my thoughts:</div><div><br></div><div>First, it's very close to the varags syntax (e.g. "Int...") which can also appear in initializer argument lists.</div><div><br></div><div>Second, and I think more important, I'm not sure that it's all that <i>useful</i>. Aside from being used to mark the initializer as having "memberwise" semantics, which is already done by the "memberwise" keyword, the most common example I've seen is code like this:</div><div><br></div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div><font face="monospace, monospace">memberwise init(customArg: Int, ...) {</font></div><div><font face="monospace, monospace"> /* use customArg */</font></div><div><font face="monospace, monospace">}</font></div></blockquote><div><br></div><div>That is, it's used to indicate where the synthesized arguments appear in the argument list if there are also custom (non-memberwise) arguments.</div><div><br></div><div>My question is, <b>why not always put the memberwise arguments last?</b> That would eliminate the need for the placeholder (aka "...").</div><div><br></div><div>I don't think I've seen a compelling case for embedding the "..." <i>within</i> a list of custom arguments, like:</div><div><br></div><div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div><span style="font-family:monospace,monospace">memberwise init(customArg1: Int, ..., customArg2: Int) {</span></div><div><span style="font-family:monospace,monospace"> /* use customArg1 and customArg2 */</span></div><div><span style="font-family:monospace,monospace">}</span><br></div></blockquote></div><div><br></div><div>And it's been mentioned several times that this is purely additive. If there <i>is</i> an obscure case where that is useful, the author can write use manual initialization.</div><div><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Jan 6, 2016 at 6:48 AM, Thorsten Seitz via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Ok, that makes sense.<br>
<br>
-Thorsten<br>
<div><div><br>
> Am 03.01.2016 um 00:24 schrieb Chris Lattner <<a href="mailto:clattner@apple.com" target="_blank">clattner@apple.com</a>>:<br>
><br>
><br>
>> On Jan 2, 2016, at 2:48 PM, Thorsten Seitz <<a href="mailto:trsfoo@googlemail.com" target="_blank">trsfoo@googlemail.com</a>> wrote:<br>
>><br>
>> One question just occurred to me: do we really need the keyword „memberwise“ anymore? Wouldn’t just using "init(…)“ be sufficient?<br>
><br>
> It wouldn’t be necessary to make the parser work, but I think we’d want something to make it clear what was intended. Otherwise, you could write:<br>
><br>
> init(a : Int, …)<br>
><br>
> when you meant:<br>
> init(a : Int …)<br>
><br>
> and unfortunate things would happen. The memberwise keyword also makes it much more clear to the reader what is going on.<br>
><br>
> -Chris<br>
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