<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Jan 17, 2018, at 1:46 PM, Itai Ferber via swift-dev <<a href="mailto:swift-dev@swift.org" class="">swift-dev@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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<div style="font-family:sans-serif" class=""><div style="white-space:normal" class=""><p dir="auto" class="">Hi Lance,</p><p dir="auto" class="">I read Michael’s emails but I don’t remember at the moment — what is the new string comparison implementation going to be based on?<br class=""></p></div></div></div></div></blockquote><div><br class=""></div><div>It is the lexicographical ordering of NFC-normalized UTF-16 code units. We use ICU to normalize strings, and there are a number of fast paths for scenarios where portions of strings are already in this canonical form.</div><br class=""><blockquote type="cite" class=""><div class=""><div class=""><div style="font-family:sans-serif" class=""><div style="white-space:normal" class=""><p dir="auto" class="">
Also, how will this affect bridged strings? If I compare two <code style="background-color:#F7F7F7; border-radius:3px; margin:0; padding:0 0.4em" bgcolor="#F7F7F7" class="">NSString</code>s, I may get a different result than if I compare the same two strings as bridged through <code style="background-color:#F7F7F7; border-radius:3px; margin:0; padding:0 0.4em" bgcolor="#F7F7F7" class="">String</code>, correct?</p></div></div></div></div></blockquote><div><br class=""></div>If they have type String (i.e. they were bridged), they will get the new ordering semantics. I’m not familiar with how the type NSString is ordered in corelibs-foundation, do you know? Either way, as a different type, NSString could independently choose different ordering semantics.</div><div><br class=""><blockquote type="cite" class=""><div class=""><div class=""><div style="font-family:sans-serif" class=""><div style="white-space:normal" class=""><p dir="auto" class="">— Itai</p><p dir="auto" class="">On 17 Jan 2018, at 13:19, Lance Parker via swift-dev wrote:</p>
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<blockquote style="border-left:2px solid #777; color:#777; margin:0 0 5px; padding-left:5px" class=""><div id="214A73A3-DA3F-4542-B204-52078D232B28" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hey Swift-Dev,<div class=""><br class=""></div><div class="">The swift standard library team have been working on a new implementation for comparing Swift strings for Swift 5. Michael touched on the motivations in the State of String email but I’ll summarize here:</div><div class=""><br class=""></div><div class=""><ul class="MailOutline"><li class="">The Swift String comparison implementations on Apple platforms and Linux differ in results and performance. Apple platforms use CFStringCompare with no locale, while Linux uses ICU libraries. Unifying the algorithms that Swift strings use for comparison is reason alone for doing a new implementation. </li><li class="">We've come up with some great common fast paths that speed up comparisons for a lot of common cases. Our microbenchmarks show up to a 6.8x increase in performance and there is still some low hanging fruit in our implementation that would bring further speedups. </li></ul></div><div class=""><br class=""></div><div class="">Bare in mind this is not intended to be a replacement for sorting strings that will be presented to users, for that developers should stick to NSLocalizedString APIs. </div></div></div></blockquote>
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