<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 Maximilian,</div><div class=""><br class=""></div><div class="">ah, I see. This is a show stopper then!</div><div class=""><br class=""></div><div class="">From what I imagine, this should not type-check:</div><div class=""><br class=""></div><div class="">var array = [1]</div><div class="">array[ifExists: 0] = nil</div><div class=""><br class=""></div><div class="">… and this should set array[0] to nil:</div><div class=""><br class=""></div><div class=""><div dir="auto" class=""><div class=""><div class=""><div dir="auto" class=""><div class=""><div class=""><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class=""><div class=""><div class=""><div class="" style="margin: 0px; line-height: normal;"><div class="" style="margin: 0px; line-height: normal;">var array: [Int?] = [1]</div><div class="" style="margin: 0px; line-height: normal;">array[ifExists: 0] = nil</div><div class="" style="margin: 0px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; line-height: normal;">Is it not possible to implement such setter in Swift?</div><div class="" style="margin: 0px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; line-height: normal;">R+</div></div></div></div></div></div></div></div></div></div></div></div></div></div><br class=""><div><blockquote type="cite" class=""><div class="">On 1 Feb 2016, at 00:07, Maximilian Hünenberger <<a href="mailto:m.huenenberger@me.com" class="">m.huenenberger@me.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="content-type" content="text/html; charset=utf-8" class=""><div dir="auto" class=""><div class=""></div><div class="">The setter of the subscript should be:</div><div class=""><div class=""><div dir="auto" class=""><div class=""><div class=""><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class=""><div class=""><blockquote class="" style="margin: 0px 0px 0px 40px; border: none; padding: 0px;"><div class=""><div class="" style="margin: 0px; line-height: normal;"><div class="" style="margin: 0px; line-height: normal;"><font class=""><span style="background-color: rgba(255, 255, 255, 0);" class=""><span class=""><br class=""></span></span></font></div><div class="" style="margin: 0px; line-height: normal;"><font class=""><span style="background-color: rgba(255, 255, 255, 0);" class=""><span class="">set</span> {</span></font></div><div class="" style="margin: 0px; line-height: normal;"><font class=""><span style="background-color: rgba(255, 255, 255, 0);" class=""> <span class="">if</span> <span class="">self</span>.indices ~= index && newValue != <span class="">nil</span> {</span></font></div><div class="" style="margin: 0px; line-height: normal;"><font class=""><span style="background-color: rgba(255, 255, 255, 0);" class=""> <span class="">self</span>[index] = newValue!</span></font></div><div class="" style="margin: 0px; line-height: normal;"><font class=""><span style="background-color: rgba(255, 255, 255, 0);" class=""> }</span></font></div><div class="" style="margin: 0px; line-height: normal;"><font class=""><span style="background-color: rgba(255, 255, 255, 0);" class="">}</span></font></div><div class="" style="margin: 0px; line-height: normal;"><font class=""><span style="background-color: rgba(255, 255, 255, 0);" class=""><br class=""></span></font></div><div class="" style="margin: 0px; line-height: normal;"><font class=""><span style="background-color: rgba(255, 255, 255, 0);" class="">Since "newValue" is of type "Element?".</span></font></div><div class="" style="margin: 0px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; line-height: normal;">It seems that this subscript could also be added to "CollectionType" and "MutableCollectionType".</div><div class="" style="margin: 0px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; line-height: normal;">The setter is weird because you can use an optional element:</div><div class="" style="margin: 0px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; line-height: normal;">var arr = [1]</div><div class="" style="margin: 0px; line-height: normal;">// is valid but doesn't set the first element</div><div class="" style="margin: 0px; line-height: normal;">arr[ifExists: 0] = nil</div><div class="" style="margin: 0px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; line-height: normal;">var arr2: [Int?] = [1]</div><div class="" style="margin: 0px; line-height: normal;">arr2[ifExists: 0] = nil // changes nothing</div><div class="" style="margin: 0px; line-height: normal;">arr2[ifExists: 0] = .Some(nil) // sets first element to nil : arr2 == [nil]</div><div class="" style="margin: 0px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; line-height: normal;">I don't know whether a setter should be added at all.</div><div class="" style="margin: 0px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; line-height: normal;">- Maximilian</div></div></div></blockquote></div></div></div></div></div></div></div></div></div><div class=""><br class="">Am 31.01.2016 um 23:38 schrieb Rudolf Adamkovič via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>>:<br class=""><br class=""></div><blockquote type="cite" class=""><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div class="">All right, I put together a proposal:</div><div class=""><br class=""></div><div class=""><a href="https://github.com/salutis/swift-evolution/blob/master/proposals/XXXX-runtime-safe-array-subscripting.md" class="">https://github.com/salutis/swift-evolution/blob/master/proposals/XXXX-runtime-safe-array-subscripting.md</a></div><div class=""><br class=""></div><div class="">… and opened a PR:</div><div class=""><br class=""></div><div class=""><a href="https://github.com/apple/swift-evolution/pull/133" class="">https://github.com/apple/swift-evolution/pull/133</a></div><div class=""><br class=""></div><div class="">Let’s see how this goes.</div><div class=""><br class=""></div><div class="">R+</div></div></blockquote></div></div></blockquote></div><br class=""></body></html>