<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="">I guess that the example doesn't make a lot of sense outside of collections, and the proposal already says that swap needs to be implemented on collections, but consider the Fisher-Yates shuffle:</div><div class=""><div class=""><pre style="font-family: monospace, Courier; background-color: rgb(248, 249, 250); border: 1px solid rgb(234, 236, 240); padding: 1em; white-space: pre-wrap; line-height: 1.3em; font-size: 14px;" class="">-- To shuffle an array <i class="">a</i> of <i class="">n</i> elements (indices 0..n-1):
<b class="">for</b> <i class="">i</i> <b class="">from</b> <i class="">n</i>−1 <b class="">downto</b> 1 <b class="">do</b>
<i class="">j</i> ← random integer such that 0 ≤ <i class="">j</i> ≤ <i class="">i</i>
exchange <i class="">a</i>[<i class="">j</i>] and <i class="">a</i>[<i class="">i</i>]</pre><div class="">I can come up with other contrived ways to force this into a dynamic analysis situation (but I am not convinced that I would ever see them in real code).</div></div></div><div class=""><br class=""></div><div class="">Also, I'm not too solid on how inout works, especially for properties without "physical storage". My understanding is that in some cases, Swift will get a direct pointer to what needs to be modified, and in others, it'll get a pointer to a temporary value and then call a setter with that temporary as the value argument. Does that sound right?</div><br class=""><div><blockquote type="cite" class=""><div class="">Le 6 mai 2017 à 10:36, John McCall <<a href="mailto:rjmccall@apple.com" class="">rjmccall@apple.com</a>> a écrit :</div><br class="Apple-interchange-newline"><div class=""><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote type="cite" class=""><div class=""><br class="Apple-interchange-newline">On May 6, 2017, at 1:11 PM, Félix Cloutier 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 class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">I have one concern and one general comment.</div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">General comment: there's a switch to turn off overflow checks for performance reasons. It seems to me that this check is going to be much more expensive than an overflow check, and it's certainly not much more likely to trigger in a release build after some amount of testing, so my opinion would be that there should be a way to turn it off globally. To me, the checking is UBSan behavior more than a language feature.</div></div></blockquote><div class=""><br class=""></div>-Ounchecked should disable this check, yes. As for "UBSan" vs. language, the general policy in Swift is to enforce its language rules by default, except in the cases of race conditions (where it would be prohibitive) and explicitly unsafe features (which are intended in part to allow things that are not possible under the normal language rules).</div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""><blockquote type="cite" class=""><div class=""><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Concern: `swap` is quoted a lot for a method that would break under this rule, but as it happens, `swap` with the same value on both sides is (should be) a no-op. Is there a way to not trip the static or dynamic checkers in well-defined cases like that one? Is there any way to check that two inout parameters refer to the same value?</div></div></blockquote><div class=""><br class=""></div>The only reasonable way to do this is statically, and why would you call 'swap' statically with the same l-value for both arguments?</div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">John.</div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""><blockquote type="cite" class=""><div class=""><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><blockquote type="cite" class=""><div class="">Le 2 mai 2017 à 13:07, Ben Cohen via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> a écrit :</div><br class="Apple-interchange-newline"><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space;"><p class="" style="-webkit-print-color-adjust: exact; margin-right: 0px; margin-bottom: 15px; margin-left: 0px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255); margin-top: 0px !important;">Hello Swift community,</p><p class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; background-color: rgb(255, 255, 255);"><span class="" style="font-family: -apple-system-body, Helvetica, arial, sans-serif;">The review of SE-0176: "</span><font face="-apple-system-body, Helvetica, arial, sans-serif" class="">Enforce Exclusive Access to Memory"</font><span class="" style="font-family: -apple-system-body, Helvetica, arial, sans-serif;"> begins now and runs through May 8, 2017.</span></p><div class=""><p class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);">The proposal is available here:</p><div class=""><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md</a></div></div><div class=""><p class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);">Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at:</p><p class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);"><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a></p><p class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);">or, if you would like to keep your feedback private, directly to the review manager. </p><p class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);">When replying, please try to keep the proposal link at the top of the message:</p><blockquote class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; border-left-width: 4px; border-left-style: solid; border-left-color: rgb(221, 221, 221); padding: 0px 15px; background-color: rgb(255, 255, 255);"><h3 id="toc_0" class="" style="color: rgb(119, 119, 119); font-family: -apple-system-body, Helvetica, arial, sans-serif; -webkit-print-color-adjust: exact; margin: 0px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 18px;">Proposal link:</h3><div class=""><font color="#777777" face="-apple-system-body, Helvetica, arial, sans-serif" class=""><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md</a></font></div><div class=""><h3 id="toc_1" class="" style="color: rgb(119, 119, 119); font-family: -apple-system-body, Helvetica, arial, sans-serif; -webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 18px;"><div class="" style="box-sizing: border-box; margin-top: 0px; margin-bottom: 0px;">Reply text</div><div class="" style="box-sizing: border-box; margin-top: 0px; margin-bottom: 0px;"><br class=""></div><blockquote class="" style="font-weight: normal; box-sizing: border-box; margin: 0px 0px 16px; padding: 0px 1em; color: rgb(106, 115, 125); border-left-width: 0.25em; border-left-style: solid; border-left-color: rgb(223, 226, 229); font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px;"><div class="" style="box-sizing: border-box; margin-top: 0px; margin-bottom: 0px;">Other replies</div></blockquote></h3><h5 class="" style="box-sizing: border-box; margin-top: 24px; margin-bottom: 16px; font-size: 0.875em; line-height: 1.25; color: rgb(36, 41, 46); font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';"><a id="user-content-what-goes-into-a-review-1" class="anchor" href="https://github.com/apple/swift-evolution#what-goes-into-a-review-1" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(3, 102, 214); text-decoration: none; float: left; padding-right: 4px; margin-left: -20px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a></h5></div></blockquote></div><div class=""><h3 id="toc_2" class="" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 18px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);">What goes into a review?</h3><p class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);">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:</p><ul class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; padding-left: 30px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);"><li class="" style="-webkit-print-color-adjust: exact; margin: 0px;">What is your evaluation of the proposal?</li><li class="" style="-webkit-print-color-adjust: exact; margin: 0px;">Is the problem being addressed significant enough to warrant a change to Swift?</li><li class="" style="-webkit-print-color-adjust: exact; margin: 0px;">Does this proposal fit well with the feel and direction of Swift?</li><li class="" style="-webkit-print-color-adjust: exact; margin: 0px;">If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?</li><li class="" style="-webkit-print-color-adjust: exact; margin: 0px;">How much effort did you put into your review? A glance, a quick reading, or an in-depth study?</li></ul><p class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);">More information about the Swift evolution process is available at:</p><p class="" style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: -apple-system-body, Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);"><a href="https://github.com/apple/swift-evolution/blob/master/process.md" class="" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196);">https://github.com/apple/swift-evolution/blob/master/process.md</a></p></div><div class=""><br class=""></div><div class="">Thanks,</div><div class="">Ben Cohen</div><div class="">Review Manager</div><div class=""><br class=""></div></div>_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br class=""></div></blockquote></div><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><span class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;">_______________________________________________</span><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><span class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;">swift-evolution mailing list</span><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><a href="mailto:swift-evolution@swift.org" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">swift-evolution@swift.org</a><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">https://lists.swift.org/mailman/listinfo/swift-evolution</a></div></blockquote></div></div></blockquote></div><br class=""></body></html>