<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="">Hi Chris,</div><div class=""><br class=""></div>Thanks for the response, I’m glad to hear that. Is this something that is planned/feasible for Swift 3?<div class=""><br class=""></div><div class="">FKL</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Dec 11, 2015, at 1:02 AM, Chris Lattner <<a href="mailto:clattner@apple.com" class="">clattner@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px; float: none; display: inline !important;" class="">On Dec 8, 2015, at 10:32 PM, Frederick Kellison-Linn via swift-evolution <</span><a href="mailto:swift-evolution@swift.org" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px;">swift-evolution@swift.org</a><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px; float: none; display: inline !important;" class="">> wrote:</span><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px;"><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px;" class=""><blockquote type="cite" class=""><br class="Apple-interchange-newline"><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">Currently, implementing an ‘<font face="SourceCodePro-Regular" class="">==</font>‘ function for a custom class can be somewhat cumbersome. In the simple hierarchy:<div class=""><br class=""></div><div class=""><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro'; color: rgb(170, 35, 145);">class<span class=""><span class="Apple-converted-space"> </span>A {</span></div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"> <span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">var</span><span class="Apple-converted-space"> </span>a:<span class="Apple-converted-space"> </span><span class="" style="color: rgb(92, 38, 153);">Int</span></div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"> <span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">init</span>(<span class="" style="color: rgb(170, 35, 145);">_</span><span class="Apple-converted-space"> </span>a:<span class="Apple-converted-space"> </span><span class="" style="color: rgb(92, 38, 153);">Int</span>) {</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"> <span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">self</span>.<span class="" style="color: rgb(79, 129, 135);">a</span><span class="Apple-converted-space"> </span>= a</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"> }</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';">}</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro'; min-height: 14px;"><br class=""></div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"><span class="" style="color: rgb(170, 35, 145);">class</span><span class="Apple-converted-space"> </span>B :<span class="Apple-converted-space"> </span><span class="" style="color: rgb(64, 110, 116);">A</span><span class="Apple-converted-space"> </span>{</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"> <span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">var</span><span class="Apple-converted-space"> </span>b:<span class="Apple-converted-space"> </span><span class="" style="color: rgb(92, 38, 153);">Int</span></div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"> <span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">init</span>(<span class="" style="color: rgb(170, 35, 145);">_</span><span class="Apple-converted-space"> </span>b:<span class="Apple-converted-space"> </span><span class="" style="color: rgb(92, 38, 153);">Int</span>,<span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">_</span><span class="Apple-converted-space"> </span>a:<span class="Apple-converted-space"> </span><span class="" style="color: rgb(92, 38, 153);">Int</span>) {</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"> <span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">self</span>.<span class="" style="color: rgb(79, 129, 135);">b</span><span class="Apple-converted-space"> </span>= b</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"> <span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">super</span>.<span class="" style="color: rgb(170, 35, 145);">init</span>(a)</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"> }</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';">}</div></div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"><br class=""></div><div class="" style="margin: 0px; line-height: normal;">A reasonable implementation of<span class="Apple-converted-space"> </span><font face="SourceCodePro-Regular" class="">==</font> would seem to be</div><div class="" style="margin: 0px; font-size: 11px; line-height: normal; font-family: 'Source Code Pro';"><br class=""></div><div class="" style="margin: 0px; line-height: normal;"><div class="" style="font-size: 11px; font-family: 'Source Code Pro'; margin: 0px; line-height: normal;"><span class="" style="color: rgb(170, 35, 145);">func</span><span class="Apple-converted-space"> </span>==(lhs:<span class="Apple-converted-space"> </span><span class="" style="color: rgb(64, 110, 116);">A</span>, rhs:<span class="Apple-converted-space"> </span><span class="" style="color: rgb(64, 110, 116);">A</span>) -><span class="Apple-converted-space"> </span><span class="" style="color: rgb(92, 38, 153);">Bool</span><span class="Apple-converted-space"> </span>{</div><div class="" style="font-size: 11px; font-family: 'Source Code Pro'; margin: 0px; line-height: normal;"> <span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">return</span><span class="Apple-converted-space"> </span>lhs.<span class="" style="color: rgb(79, 129, 135);">a</span><span class="Apple-converted-space"> </span>== rhs.<span class="" style="color: rgb(79, 129, 135);">a</span></div><div class="" style="font-size: 11px; font-family: 'Source Code Pro'; margin: 0px; line-height: normal;">}</div><div class="" style="font-size: 11px; font-family: 'Source Code Pro'; margin: 0px; line-height: normal; min-height: 14px;"><br class=""></div><div class="" style="font-size: 11px; font-family: 'Source Code Pro'; margin: 0px; line-height: normal;"><span class="" style="color: rgb(170, 35, 145);">func</span><span class="Apple-converted-space"> </span>==(lhs:<span class="Apple-converted-space"> </span><span class="" style="color: rgb(64, 110, 116);">B</span>, rhs:<span class="Apple-converted-space"> </span><span class="" style="color: rgb(64, 110, 116);">B</span>) -><span class="Apple-converted-space"> </span><span class="" style="color: rgb(92, 38, 153);">Bool</span><span class="Apple-converted-space"> </span>{</div><div class="" style="font-size: 11px; font-family: 'Source Code Pro'; margin: 0px; line-height: normal;"> <span class="Apple-converted-space"> </span><span class="" style="color: rgb(170, 35, 145);">return</span><span class="Apple-converted-space"> </span>lhs.<span class="" style="color: rgb(79, 129, 135);">a</span><span class="Apple-converted-space"> </span>== rhs.<span class="" style="color: rgb(79, 129, 135);">a</span><span class="Apple-converted-space"> </span>&&</div><div class="" style="font-size: 11px; font-family: 'Source Code Pro'; margin: 0px; line-height: normal;"> lhs.<span class="" style="color: rgb(79, 129, 135);">b</span><span class="Apple-converted-space"> </span>== rhs.<span class="" style="color: rgb(79, 129, 135);">b</span></div><div class="" style="font-size: 11px; font-family: 'Source Code Pro'; margin: 0px; line-height: normal;">}</div><div class="" style="font-size: 11px; font-family: 'Source Code Pro'; margin: 0px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; line-height: normal;"><div class="" style="margin: 0px; line-height: normal;"><div class="" style="margin: 0px; line-height: normal;">I’d be interested to know if there is any interest taken in this problem and whether possible solutions have been discussed. If<span class="Apple-converted-space"> </span><font face="SourceCodePro-Regular" class="">==</font> were instead behaved as if it were a method of its first argument (as in a<span class="Apple-converted-space"> </span><font face="SourceCodePro-Regular" class="">.equals(other)</font> method) then the solution above is sufficient to avoid returning the wrong result, but being forced to use <span class="" style="font-family: 'Source Code Pro';">.</span><span class="" style="font-family: 'Source Code Pro'; color: rgb(170, 35, 145);">dynamicType</span><span class="" style="font-family: 'Source Code Pro';"> </span>for something as basic as equality checking seems cumbersome to me.</div></div></div></div></div></div></blockquote><br class=""></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px;" class="">Hi Frederick,</div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px;" class=""><br class=""></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px;" class="">The preferred approach is to allow operators to be defined inside of types. This would allow them to be dynamically dispatched inside of classes.</div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px;" class=""><br class=""></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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-stroke-width: 0px;" class="">-Chris</div></div></blockquote></div><br class=""></div></body></html>