<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Currently, we have the Repeated<T> type, which presents a single element as though it were a Collection. <div class=""><div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><font face="Courier" class="">> for i in repeatElement(1, count: 3) { print(i) }</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class=""><br class=""></font></div><div class=""><font face="Courier" class="">> for i in repeatElement([1, 2, 3], count: 3) { print(i) }</font></div><div class=""><font face="Courier" class="">[1, 2, 3]</font></div><div class=""><font face="Courier" class="">[1, 2, 3]</font></div><div class=""><font face="Courier" class="">[1, 2, 3]</font></div></blockquote><div class=""><br class=""></div><div class="">However, we lack the ability for Collections to repeat their contents in a single list; basically, some kind of “flatMap” to repeatElement’s “map”. So I’d like to pitch a new API for repeated values. </div><div class=""><br class=""></div><div class="">- We would add a RepeatCollection<C: Collection> type, which loops over its base Collection a certain number of times (or until a maximum ‘count’). </div><div class=""> Implementation might look something like this (<a href="https://gist.github.com/karwa/5228974a0b4dfd000a916f0aac2721c6" class="">https://gist.github.com/karwa/5228974a0b4dfd000a916f0aac2721c6</a>), except that we’d add some optimised map(), filter() and contains() functions which apply the algorithm once to the base and multiply the result.</div><div class=""><br class=""></div><div class="">- We would add 3 new functions to all Collections:</div><div class=""><br class=""></div></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><div class=""><font face="Courier" class="">/// Repeats the collection <i class="">itself</i> N times.</font></div></div><div class=""><div class=""><font face="Courier" class="">///</font></div></div><div class=""><div class=""><font face="Courier" class="">func repeated(_ times: Int) -> RepeatCollection<CollectionOfOne<Self>></font></div></div><div class=""><div class=""><font face="Courier" class=""><br class=""></font></div></div><div class=""><div class=""><font face="Courier" class="">/// Repeats the collection’s <i class="">contents</i> N times.</font></div></div><div class=""><div class=""><font face="Courier" class="">///</font></div></div><div class=""><div class=""><font face="Courier" class="">func repeatElements(_ times: Int) -> RepeatCollection<Self></font></div></div><div class=""><div class=""><font face="Courier" class=""><br class=""></font></div></div><div class=""><div class=""><font face="Courier" class="">/// Loops the collection’s contents to present a Collection of length N.</font></div></div><div class=""><div class=""><font face="Courier" class="">///</font></div></div><div class=""><div class=""><font face="Courier" class="">func repeatElements(count: Int) -> RepeatCollection<Self></font></div></div></blockquote><div class=""><div class=""><br class=""></div><div class="">- We would replace the existing Repeated<T> type with a typealias to RepeatCollection<CollectionOfOne<T>></div><div class="">- The existing, top-level repeatElement(T, Int) function <i class="">could</i> stay, but could also be replaced with an incantation on CollectionOfOne. I’m fairly ambivalent about this point - it’d be nice to see the function go, but the replacement also isn’t obvious.</div><div class=""><br class=""></div><div class="">Example usage of the new API:</div><div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><font face="Courier" class="">// Equivalent to repeatElement(1, count: 3)</font></div><div class=""><font face="Courier" class=""><br class=""></font></div><div class=""><font face="Courier" class="">> for i in CollectionOfOne(1).repeatElements(3).forEach { print(i) }</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class=""><br class=""></font></div><div class=""><font face="Courier" class="">// Equivalent to repeatElement([1, 2, 3], count: 3)</font></div><div class=""><font face="Courier" class=""><br class=""></font></div><div class=""><div class=""><font face="Courier" class="">> for i in [1, 2, 3].repeated(3).forEach { print(i) }</font></div><div class=""><font face="Courier" class="">[1, 2, 3]</font></div><div class=""><span style="font-family: Courier;" class="">[1, 2, 3]</span></div><div class=""><span style="font-family: Courier;" class="">[1, 2, 3]</span></div></div><div class=""><span style="font-family: Courier;" class=""><br class=""></span></div><div class=""><span style="font-family: Courier;" class="">// New, flat repetition</span></div><div class=""><font face="Courier" class=""><br class=""></font></div><div class=""><font face="Courier" class="">> for i in [1, 2, 3].repeatElements(3) { print(i) }</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class="">2</font></div><div class=""><font face="Courier" class="">3</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class="">2</font></div><div class=""><font face="Courier" class="">3</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class="">2</font></div><div class=""><font face="Courier" class="">3</font></div><div class=""><font face="Courier" class=""><br class=""></font></div><div class=""><div class=""><span style="font-family: Courier;" class="">// New, flat repetition</span></div><div class=""><font face="Courier" class=""><br class=""></font></div><div class=""><font face="Courier" class="">> for i in [1, 2, 3].repeatElements(count: 4) { print(i) }</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><font face="Courier" class="">2</font></div><div class=""><font face="Courier" class="">3</font></div><div class=""><font face="Courier" class="">1</font></div><div class=""><br class=""></div></div><div class=""><font face="Courier" class="">// Additional benefit: you can now repeat slices!</font></div><div class=""><font face="Courier" class=""><br class=""></font></div><div class=""><font face="Courier" class="">> String(“yellow”.characters.dropFirst().dropLast().repeat(times: 3))</font></div><div class=""><font face="Courier" class="">“elloelloello"</font></div><div class=""><br class=""></div><div class=""><br class=""></div></blockquote>Thoughts?</div><div class=""><br class=""></div><div class="">- Karl<br class=""><div class=""><br class=""></div></div></body></html>