<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><blockquote type="cite" class="">On May 10, 2016, at 11:53 AM, Chris Lattner via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class="">Hello Swift community,<br class=""><br class="">The review of "SE-0084: Allow trailing commas in parameter lists and tuples" begins now and runs through May 16. The proposal is available here:<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0084-trailing-commas.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0084-trailing-commas.md</a><br class=""><br class="">Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>https://lists.swift.org/mailman/listinfo/swift-evolution<br class=""><br class="">or, if you would like to keep your feedback private, directly to the review manager.<br class=""><br class="">What goes into a review?<br class=""><br class="">The goal of the review process is to improve the proposal under review through constructive criticism and contribute to the direction of Swift. When writing your review, here are some questions you might want to answer in your review:<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* What is your evaluation of the proposal?<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* Is the problem being addressed significant enough to warrant a change to Swift?<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* Does this proposal fit well with the feel and direction of Swift?<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* How much effort did you put into your review? A glance, a quick reading, or an in-depth study?<br class=""><br class="">More information about the Swift evolution process is available at<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>https://github.com/apple/swift-evolution/blob/master/process.md<br class=""><br class="">Thank you,<br class=""><br class="">-Chris Lattner<br class="">Review Manager<br class=""></blockquote><br class=""><div class="">+1 from me. We should be consistent in either accepting or rejecting trailing commas everywhere we have comma-delimited syntax. I'm in favor of accepting it, since it's popular in languages where it's supported to enable a minimal-diff style, so that changes to code don't impact neighboring lines for purely syntactic reasons. If you add an argument to a function, without trailing comma support, a comma has to be added to dirty the previous line:</div><div class=""><br class=""></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>--- a.swift</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>+++ a.swift</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span> foo(</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span> x: 0,</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>- y: 1</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>+ y: 1,</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>+ z: 2</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span> )</font></div><div class=""><br class=""></div><div class="">Trailing commas avoid this:</div><div class=""><br class=""></div><div class=""><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>--- a.swift</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>+++ a.swift</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space: pre;"> </span> foo(</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space: pre;"> </span> x: 0,</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space: pre;"> </span> y: 1,</font></div><div class=""><span class="Apple-tab-span" style="font-family: Menlo; white-space: pre;"> </span><span style="font-family: Menlo;" class="">+ z: 2,</span></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space: pre;"> </span> )</font></div></div><div class=""><font face="Menlo" class=""><br class=""></font></div><div class=""><br class=""></div><div class="">In languages that don't support trailing commas, many users resort to the abomination of leading-comma style, strangely popular in Haskell and related languages:</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>--- a.swift</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>+++ a.swift</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span> foo( x: 0</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span> , y: 1</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>+ , z: 2</font></div><div class=""><font face="Menlo" class=""><span class="Apple-tab-span" style="white-space:pre"> </span> )</font></div><div class=""><br class=""></div><div class="">I think the trailing-comma syntax jives much better with Swift style.</div><div class=""><br class=""></div><div class="">-Joe</div></body></html>