<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 still like the ordering of floats defined in this proposal best (and think we should use it), but I imagine that there are other types which are almost (but not quite) comparable as well. Would there be any utility in having a ‘PartialComparable’ protocol that defined a single method:</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func compare(_:)->ComparisonResult?</div><div class=""><br class=""></div><div class="">That is, it is just like our compare, but it returns nil if two values can’t be meaningfully compared. It would force you to deal with the cases where the comparison didn’t make sense, and handle it in a reasonable way in your code. (e.g. filtering those values out, or sticking them at the end).</div><div class=""><br class=""></div><div class="">You can think of it as failable compare...</div><div class=""><br class=""></div><div class="">Thanks,</div><div class="">Jon</div><div class=""><br class=""></div><br class=""><div><blockquote type="cite" class=""><div class="">On Apr 13, 2017, at 1:17 PM, Ben Cohen via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><div class=""><h3 id="partialcomparable" class="" style="font-style: normal; font-variant-caps: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; color: rgb(17, 17, 17); margin: 21px 0px; font-size: 20px; line-height: 21px; font-family: 'Helvetica Neue', Helvetica, Arial, Verdana, sans-serif;">PartialComparable</h3><p class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; color: rgb(17, 17, 17); font-family: 'Helvetica Neue', Helvetica, Arial, Verdana, sans-serif; word-wrap: break-word; margin: 1.3125em 0px; font-size: 1.1429em; line-height: 1.3125em;">PartialComparable would essentially just be Comparable without any stated ordering requirements, that Comparable extends to provide ordering requirements. This would be a protocol that standard IEEE comparison could satisfy, but in the absence of total ordering requirements, PartialComparable is effectively useless. Either everyone would consume PartialComparable (to accept floats) or Comparable (to have reasonable behaviour).</p><p class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; color: rgb(17, 17, 17); font-family: 'Helvetica Neue', Helvetica, Arial, Verdana, sans-serif; word-wrap: break-word; margin: 1.3125em 0px; font-size: 1.1429em; line-height: 1.3125em;">The Rust community adopted this strategy to little benefit. The Rust libs team has frequently considered removing the distinction, but hasn’t because doing it backwards compatibly would be complicated. Also because merging the two would just lead to the problems Swift has today.</p></div></blockquote></div><br class=""></body></html>