<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><div class=""><div class=""><font face="HelveticaNeue" class=""><b class="">Review of SE-0007</b></font></div><div class=""><font face="HelveticaNeue" class=""><b class=""><br class=""></b></font></div><div class=""><font face="HelveticaNeue" class=""><b class="">* What is your evaluation of the proposal?</b></font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class="">This is a sensible change. I am in favor of it.</font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class=""><b class="">* Is the problem being addressed significant enough to warrant a change to Swift?</b></font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class="">In isolation, the problem appears too small to warrant a change — just a little cruft in the language, an unnecessary but mostly harmless remnant of Swift’s ancestry. The C-style for loop is not a common source of programmer error, and is easy for the compiler to implement.</font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class="">However, in aggregate, cruft like this leads to language bloat and stagnation. In a garden, a single weed is not a problem, but <i class="">never weeding</i> is a significant problem.</font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><span style="font-family: HelveticaNeue;" class="">We have a feature that is:</span><br style="font-family: HelveticaNeue;" class=""><br style="font-family: HelveticaNeue;" class=""><span style="font-family: HelveticaNeue;" class="">1. not widely used,</span><br style="font-family: HelveticaNeue;" class=""><span style="font-family: HelveticaNeue;" class="">2. easily replaced with other languages features where it is used, and</span><br style="font-family: HelveticaNeue;" class=""><span style="font-family: HelveticaNeue;" class="">3. inconsistent with the language’s general aesthetic.</span><br style="font-family: HelveticaNeue;" class=""><br style="font-family: HelveticaNeue;" class=""><span style="font-family: HelveticaNeue;" class="">Observation, theory, and taste agree. If this isn’t a feature to remove for the health of the language, then what is? If we do not pull this weed, then what weed would we ever pull?</span></div><div class=""><span style="font-family: HelveticaNeue;" class=""><br class=""></span></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class=""><b class="">* Does this proposal fit well with the feel and direction of Swift?</b></font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class="">Yes.</font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class="">1. Swift tends to favor concise language constructs over boilerplate code for common patterns (e.g. didSet, lazy, optional unwrapping conveniences). This makes the C-style for out of place for the two common cases, counting and collection iteration, both of which already have more Swift-like alternatives.</font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class="">2. The ++ and — operators are already slated for removal, which makes the C-style for much less compelling.</font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><span style="font-family: HelveticaNeue;" class="">3. Swift tends to encourage immutability. It’s a minor detail, but the fact that the C-style for rules out immutability for the index variable is particularly compelling to me:</span></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><div style="margin: 0px; font-size: 10.5px; line-height: normal; font-family: Menlo; color: rgb(102, 139, 73);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #323e7d" class="">for</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> i </span><span style="font-variant-ligatures: no-common-ligatures; color: #323e7d" class="">in</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #323e7d" class="">0</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">..<</span><span style="font-variant-ligatures: no-common-ligatures; color: #323e7d" class="">16</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span>// i is immutable by default</div><div style="margin: 0px; font-size: 10.5px; line-height: normal; font-family: Menlo;" class=""><br class=""></div><div style="margin: 0px; font-size: 10.5px; line-height: normal; font-family: Menlo;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #323e7d" class="">for</span> <span style="font-variant-ligatures: no-common-ligatures; color: #323e7d" class="">let</span> i = <span style="font-variant-ligatures: no-common-ligatures; color: #323e7d" class="">0</span>; i < <span style="font-variant-ligatures: no-common-ligatures; color: #323e7d" class="">16</span>; i++ <span style="font-variant-ligatures: no-common-ligatures; color: #668b49" class="">// doesn't work</span></div><div style="margin: 0px; font-size: 10.5px; line-height: normal; font-family: Menlo;" class=""><br class=""></div></div><div class=""><font face="HelveticaNeue" class="">4. The few cases raised on the list where C-style for <i class="">might</i> still be preferable over other loop constructs all involve subtle interaction between the iterator clause (third part of the “for”) and break/continue/return. When I’ve seen this kind of code in the wild, at least in my own experience, it (1) </font><span style="font-family: HelveticaNeue;" class="">usually is brittle and in need of rewriting, and</span><font face="HelveticaNeue" class=""> </font><span style="font-family: HelveticaNeue;" class="">(2) </span><font face="HelveticaNeue" class="">tends to appear only in low-level system libraries and graphics-related bit-twiddling, neither of which seem like Swift’s areas of focus. (Swift’s favoring of explicit scalar type conversion and precision safety already make it ill-suited to low-level bit twiddling.)</font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class=""><b class="">* If you have you used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?</b></font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class="">Ruby does not have a C-style for loop. I’ve used Ruby extensively since 2007, and have not once felt that I wanted a C-style for.</font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class=""><br class=""></font></div><div class=""><font face="HelveticaNeue" class=""><b class="">* How much effort did you put into your review? A glance, a quick reading, or an in-depth study?</b></font></div><div class=""><br class=""></div></div></div><div class="">An hour or two. I’ve followed the discussion on the mailing list. I did a programmatic search of all of my own Swift code; I’ve never used the C-style for in Swift.</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><br class=""><div><blockquote type="cite" class=""><div class="">On Dec 7, 2015, at 2:44 PM, Douglas Gregor via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hello Swift community,<br class=""><br class="">The review of "Remove C-style for-loops with conditions and incrementers” begins now and runs through Thursday, December 10th. The proposal is available here:<div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0007-remove-c-style-for-loops.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0007-remove-c-style-for-loops.md</a></div><div class=""><br class=""></div><div class="">Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a></div><div class=""><br class=""></div><div class="">or, if you would like to keep your feedback private, directly to the review manager.</div><div class=""><br class=""></div><div class="">What goes into a review?</div><div class=""><br class="">The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:<br class=""><br class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* What is your evaluation of the proposal?<br class=""></div><div 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=""></div><div 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=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* If you have you used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?<br class=""></div><div 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=""></div><br class=""></div><div class="">More information about the Swift evolution process is available at</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span><a href="https://github.com/apple/swift-evolution/blob/master/process.md" class="">https://github.com/apple/swift-evolution/blob/master/process.md</a></div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>Cheers,</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>Doug Gregor</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>Review Manager</div><div class=""><br class=""></div>
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