<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 Jan 27, 2017, at 4:55 PM, Karl Wagner <<a href="mailto:razielim@gmail.com" class="">razielim@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=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On 27 Jan 2017, at 22:25, Slava Pestov <<a href="mailto:spestov@apple.com" class="">spestov@apple.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=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jan 27, 2017, at 11:44 AM, Karl Wagner 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="">So, 2 quick points:<br class=""><div class=""><br class=""></div><div class="">1) I have often wanted a shorthand for expressing long tuples; I definitely think that’s something worth bike-shedding, e.g. - <font face="Courier" class="">(String * 4, Int32 * 4)</font> or something</div></div></div></blockquote><div class=""><br class=""></div>Why not define a struct, or a tuple consisting of two arrays?</div></div></div></blockquote><div class=""><br class=""></div>Because I want a fixed-length guarantee; <font face="Courier" class="">([String], [Int])</font> could have any number of Strings or Ints.</div></div></div></blockquote><div><br class=""></div>Ok, maybe a struct would named fields would be better though.</div><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="">It’s just a shorthand for defining long or complex tuples; we currently import C arrays as massive tuples which can be basically impossible to read.</div></div></div></blockquote><div><br class=""></div>I agree that this is a problem — fixed length arrays should be imported better, once we have the right language features.</div><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=""><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=""><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="">2) Having a special non-growing array type which is called “array” and separate from <font face="Courier" class="">Array<T></font> is not such a good idea IMO. I would rather allow tuples to conform to protocols (see: <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=""><br class=""></div><div class="">If tuples could conform to protocols, we could say “any tuple of homogenous elements is a <font face="Courier" class="">Collection</font>”. There would be benefits for the standard library, too - <font face="Courier" class="">EmptyCollection<T></font> would disappear, replaced with the empty tuple <font face="Courier" class="">()</font>,</div></div></div></blockquote><div class=""><br class=""></div>This sounds too clever.</div></div></div></blockquote><div class=""><br class=""></div><div class="">Yeah… the cleverness is one of things I <i class="">like</i> about it. We get to remove these canned conformances and reduce the stdlib surface area while gaining an efficient way to express a fixed-size Collection. It would come with all kinds of supplementary benefits, such as iterating and mapping the elements of a tuple.</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=""><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=""> as would <font face="Courier" class="">CollectionOfOne<T></font>, to be replaced by a single-element tuple <font face="Courier" class="">(T)</font>.</div></div></div></blockquote><div class=""><br class=""></div><div class="">For what it’s worth, Swift doesn’t have single-element tuples. (T) is just sugar for the type T itself.</div></div></div></div></blockquote><div class=""><br class=""></div><div class="">Would it be unreasonable to separate those, so that (T) is separate from T instead of being a synonym for it? There is some awkwardness with tuples due to legacy designs. Perhaps this would help clean it up a little (or perhaps make it worse, who knows?)</div><div class=""><br class=""></div><div class="">For source compatibility, we could allow an implicit conversion; in the same way that a T can be implicitly “promoted" to an Optional<T>, it could be implicitly “promoted” to a single-element tuple of T (and vice-versa).</div></div></div></div></blockquote><div><br class=""></div>Sure, we *could* re-design tuple types in a way where single element tuples make sense. Then we’d have to come up with a source compatibility story for Swift 3 vs Swift 4, fix any fallout (compiler crashes) from this change, implement migrator support when the stdlib is changed to use the new features, etc. But think of it this way — every such “unnecessary” change (and I realize this is subjective!) is taking away cycles the team could use to fix crashes, improve compiler speed, and improve diagnostics. Not to mention implementing the other evolution proposals which arguably increase expressive power in important ways we feel we need for ABI stability, such as generic subscripts.</div><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=""><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=""><div class=""><br class=""></div><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=""> We would also be able to remove our limited-arity <font face="Courier" class="">==</font> overloads in favour of actual, honest-to-goodness <font face="Courier" class="">Equatable</font> conformance.</div></div></div></blockquote><div class=""><br class=""></div>I like this idea though.</div><div class=""><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="">- Karl</div><a href="https://github.com/apple/swift/blob/master/docs/GenericsManifesto.md#extensions-of-structural-types" class=""></a></div>_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br class=""></div></blockquote></div><br class=""></div></div></blockquote></div><br class=""></div></div></blockquote></div><br class=""></body></html>