<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="">On 9. Jul 2017, at 21:20, David Baraff <<a href="mailto:davidbaraff@gmail.com" class="">davidbaraff@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Nice: i hadn’t seen elementsEqual.<div class=""><br class=""></div><div class=""> (1) Why do you have to pass in “by: ==“ ? is not that the default</div></div></div></blockquote><div><br class=""></div><div>There are two versions: One taking an explicit predicate, and another which requires sequences of Equatable elements. As observed earlier in this thread, an array of tuples is not Equatable.</div><br class=""><blockquote type="cite" class=""><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><br class=""></div><div class=""> (2) not a big deal, but if the sequence type’s length can be determined a priori (e.g. in the case of an Array, or perhaps a Collection if that has a count member, haven’t checked) does the elementsEqual function short circuit by first checking that the lengths are equal before beginning the loop?</div></div></div></blockquote><div><br class=""></div><div>As far as I can tell from the implementation at <a href="https://github.com/apple/swift/blob/master/stdlib/public/core/SequenceAlgorithms.swift.gyb#L292" class="">https://github.com/apple/swift/blob/master/stdlib/public/core/SequenceAlgorithms.swift.gyb#L292</a> , the length is not checked a-priori, so you might want to add that to your code:</div><div><br class=""></div><div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">class</span><span style="font-variant-ligatures: no-common-ligatures" class=""> Tree : </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Equatable</span><span style="font-variant-ligatures: no-common-ligatures" class=""> {</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> rootData:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span><span style="font-variant-ligatures: no-common-ligatures" class=""> = </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">0</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> children:[(</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Tree</span><span style="font-variant-ligatures: no-common-ligatures" class="">)] = []</span></div><p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><br class="webkit-block-placeholder"></p><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">static</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">public</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> ==(</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> lhs:</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Tree</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> rhs:</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Tree</span><span style="font-variant-ligatures: no-common-ligatures" class="">) -> </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Bool</span><span style="font-variant-ligatures: no-common-ligatures" class=""> {</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">return</span><span style="font-variant-ligatures: no-common-ligatures" class=""> lhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">rootData</span><span style="font-variant-ligatures: no-common-ligatures" class=""> == rhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">rootData</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">&&</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> lhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">children</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">count</span><span style="font-variant-ligatures: no-common-ligatures" class=""> == rhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">children</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">count</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">&&</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> lhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">children</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">elementsEqual</span><span style="font-variant-ligatures: no-common-ligatures" class="">(rhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">children</span><span style="font-variant-ligatures: no-common-ligatures" class="">, by: ==)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div><div><br class=""></div><br class=""><blockquote type="cite" class=""><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><br class=""></div><div class=""><div class=""><div class="">But again, that’s a great one to know.</div><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jul 9, 2017, at 12:14 PM, Martin R via swift-users <<a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On 9. Jul 2017, at 21:00, Jens Persson via swift-users <<a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" style="font-family: Helvetica; font-size: 13px; 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="">Since Array has .elementsEqual, another workaround (until conditional conformance) is:<div class=""><br class=""></div><div class=""><div class="">class Tree : Equatable {</div><div class=""> let rootData:Int</div><div class=""> let children:[(String, Tree)]</div><div class=""> </div><div class=""> init(rootData: Int, children: [(String, Tree)]) {</div><div class=""> self.rootData = rootData</div><div class=""> self.children = children</div><div class=""> }</div><div class=""> static public func ==(_ lhs:Tree, _ rhs:Tree) -> Bool {</div><div class=""> return lhs.rootData == rhs.rootData &&</div><div class=""> lhs.children.elementsEqual(rhs.children, by: { (a: (String, Tree), b: (String, Tree)) -> Bool in</div><div class=""> return a.0 == b.0 && a.1 == b.1</div><div class=""> })</div><div class=""> }</div><div class="">}</div></div></div></div></blockquote><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Slightly simpler (since == is already defined for the tuples):</div><div class=""><br class=""></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">class</span><span style="font-variant-ligatures: no-common-ligatures" class=""> Tree : </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Equatable</span><span style="font-variant-ligatures: no-common-ligatures" class=""> {</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> rootData:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span><span style="font-variant-ligatures: no-common-ligatures" class=""> = </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">0</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> children:[(</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Tree</span><span style="font-variant-ligatures: no-common-ligatures" class="">)] = []</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><br class="webkit-block-placeholder"></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">static</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">public</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> ==(</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> lhs:</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Tree</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> rhs:</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Tree</span><span style="font-variant-ligatures: no-common-ligatures" class="">) -> </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Bool</span><span style="font-variant-ligatures: no-common-ligatures" class=""> {</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">return</span><span style="font-variant-ligatures: no-common-ligatures" class=""> lhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">rootData</span><span style="font-variant-ligatures: no-common-ligatures" class=""> == rhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">rootData</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">&&</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> lhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">children</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">elementsEqual</span><span style="font-variant-ligatures: no-common-ligatures" class="">(rhs.</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">children</span><span style="font-variant-ligatures: no-common-ligatures" class="">, by: ==)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" style="font-family: Helvetica; font-size: 13px; 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=""><br class=""></div></div><div class="gmail_extra" style="font-family: Helvetica; font-size: 13px; 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 class="gmail_quote">On Sun, Jul 9, 2017 at 8:44 PM, David Sweeris<span class="Apple-converted-space"> </span><span dir="ltr" class=""><<a href="mailto:davesweeris@mac.com" target="_blank" class="">davesweeris@mac.com</a>></span><span class="Apple-converted-space"> </span>wrote:<br class=""><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex;"><div dir="auto" class=""><span class=""><div class=""><br class=""></div><div class="">On Jul 9, 2017, at 10:06, David Baraff via swift-users <<a href="mailto:swift-users@swift.org" target="_blank" class="">swift-users@swift.org</a>> wrote:<br class=""><br class=""></div><blockquote type="cite" class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jul 9, 2017, at 8:27 AM, Jens Persson <<a href="mailto:jens@bitcycle.com" target="_blank" class="">jens@bitcycle.com</a>> wrote:</div><br class="m_-7025976968143332599Apple-interchange-newline"><div class=""><div dir="ltr" class="">(Also, note that your implementation of == uses lhs === rhs thus will only return true when lhs and rhs are the same instance of SomeClass.)</div></div></blockquote><div class="">Of course — i threw that in just to make a simple example.</div><div class=""><br class=""></div><div class="">Followup question: what I really wanted to write was an == operator for a tree:</div><div class=""><br class=""></div><div class="">// silly tree, useful for nothing</div><div class="">class Tree : Equatable {</div><div class=""> let rootData:Int</div><div class=""> let children:[(String, Tree)]</div><div class=""><br class=""></div><div class=""> static public func ==(_ lhs:Tree, _ rhs:Tree) {</div><div class=""><span class="m_-7025976968143332599Apple-tab-span" style="white-space: pre-wrap;"> </span>return lhs.rootData == rhs.rootData && </div><div class=""> <span class="Apple-converted-space"> </span>lhs.children == rhs.children<span class="m_-7025976968143332599Apple-tab-span" style="white-space: pre-wrap;"> </span>// sadly, this doesn’t compile</div><div class=""> }</div><div class="">}</div></div></blockquote><br class=""></span><div class="">Right, the `==` func is *defined* for 2-element tuples where both elements conform to `Equatable`, but that tuple type doesn't itself *conform* to `Equatable`. So the<span style="background-color: rgba(255, 255, 255, 0);" class="">`==` func that's defined on "Array where Element: Equatable" can't see it.</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);" class=""><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);" class="">We'd need both "conditional conformance" and "tuple conformance" in order for that to Just Work.</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);" class=""><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);" class="">- Dave Sweeris </span></div></div></blockquote></div><br class=""></div><span style="font-family: Helvetica; font-size: 13px; 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;" class="">_______________________________________________</span><br style="font-family: Helvetica; font-size: 13px; 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=""><span style="font-family: Helvetica; font-size: 13px; 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;" class="">swift-users mailing list</span><br style="font-family: Helvetica; font-size: 13px; 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=""><a href="mailto:swift-users@swift.org" style="font-family: Helvetica; font-size: 13px; 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;" class="">swift-users@swift.org</a><br style="font-family: Helvetica; font-size: 13px; 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=""><a href="https://lists.swift.org/mailman/listinfo/swift-users" style="font-family: Helvetica; font-size: 13px; 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;" class="">https://lists.swift.org/mailman/listinfo/swift-users</a></div></blockquote></div><br class=""></div>_______________________________________________<br class="">swift-users mailing list<br class=""><a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-users" class="">https://lists.swift.org/mailman/listinfo/swift-users</a><br class=""></div></blockquote></div><br class=""></div></div></div></div></div></blockquote></div><br class=""></body></html>