<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=""><br class=""><div><blockquote type="cite" class=""><div class="">Am 18.10.2017 um 22:36 schrieb Michael Ilseman <<a href="mailto:milseman@apple.com" class="">milseman@apple.com</a>>:</div><div class=""><blockquote type="cite" class="" style="font-family: HelveticaNeue; font-size: 14px; 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;"><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;">To get back to the topic at hand: I propose to differentiate between unordered and ordered collections because I think that this is an important distinction with tractable impact on algorithms (as shown above). The method `elementsEqual` would be part of the ordered sequence protocol and I would suggest the name `elementsPairwiseEqual`.</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></blockquote><div style="font-family: HelveticaNeue; font-size: 14px; 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: HelveticaNeue; font-size: 14px; 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=""><div class="">You are free to propose that and justify its cost. You'll probably want to plan on how you’ll present the cost/benefit analysis for the feedback of “why not just slap a warning on Set/Dictionary?”</div></div></div></blockquote><br class=""></div><div>The warning will have to be slapped on `Sequence` because I and others can write types adopting Sequence but being unordered.</div><div><br class=""></div><div>And it will have to be slapped on every public generic function written by anyone which takes a Sequence as argument and internally uses `elementsEqual` on that argument, so that the user of such an API knows that he cannot use that function with a Set or another unordered subtype of Sequence.</div><div><br class=""></div><div>-Thorsten</div><br class=""></body></html>