<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 16 Oct 2016, at 00:33, Haravikk via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@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 15 Oct 2016, at 18:21, Nevin Brackett-Rozinsky <<a href="mailto:nevin.brackettrozinsky@gmail.com" class="">nevin.brackettrozinsky@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Tuples cannot conform to protocols, so despite the existence of an “==” operator for certain tuples, no tuple conforms to Equatable.<div class=""><br class=""></div><div class="">This is problematic, because it means that a function which takes a generic Equatable parameter cannot be called with a tuple argument, even though an applicable “==” operator exists.</div><div class=""><br class=""></div><div class="">(Ditto for “Comparable”, <i class="">mutatis mutandis</i>.)</div><div class=""><br class=""></div><div class="">Nevin</div></div></div></blockquote><br class=""></div><div class="">Yeah, since the operators are implemented though perhaps some kind of magic can be used? It seems strange that the following is valid:</div><div class=""><br class=""></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>struct Foo : Equatable { let value:(Int, Int) }</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func == (lhs:Foo, rhs:Foo) -> Bool { return lhs.value == rhs.value }</font></div><div class=""><br class=""></div><div class="">Yet tuples can't just be Equatable etc. But I'm wondering whether that falls into separate issue territory, such that it should be done first as its own proposal?</div></div>_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class="">https://lists.swift.org/mailman/listinfo/swift-evolution<br class=""></div></blockquote></div><br class=""><div class="">Tuples are non-nominal (named) types, and that’s why they can’t conform to protocols. There is something in the generics manifesto about possibly allowing them to do that in the future, though: <div class=""><br class=""></div><div class=""><a href="https://github.com/apple/swift/blob/master/docs/GenericsManifesto.md#extensions-of-structural-types" class="">https://github.com/apple/swift/blob/master/docs/GenericsManifesto.md#extensions-of-structural-types</a></div><div class=""><blockquote type="cite" class=""><h3 style="box-sizing: border-box; margin-top: 24px; margin-bottom: 16px; font-size: 1.25em; line-height: 1.25; color: rgb(51, 51, 51); font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class="">Extensions of structural types</h3><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">Currently, only nominal types (classes, structs, enums, protocols) can be extended. One could imagine extending structural types—particularly tuple types—to allow them to, e.g., conform to protocols. For example, pulling together variadic generics, parameterized extensions, and conditional conformances, one could express "a tuple type is <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 13.600000381469727px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Equatable</code> if all of its element types are <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 13.600000381469727px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">Equatable</code>":</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 13.600000381469727px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; word-wrap: normal; padding: 16px; overflow: auto; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);"><...</span>Elements <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Equatable</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">></span> (Elements<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">...</span>) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Equatable</span> { <span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">// extending the tuple type "(Elements...)" to be Equatable</span>
}</pre></div></blockquote><div class=""><br class=""></div></div><div class=""><br class=""></div><div class="">- Karl<br class=""></div></div><div class=""><br class=""></div></body></html>