<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="">I see, the really issue I'm trying to bring up is that <span class="" style="color: rgb(69, 69, 69); font-family: 'Helvetica Neue';">removeLast() can easily fail (and result in a fatal error).</span><div class=""><font color="#454545" face="Helvetica Neue" class="">And unless you read the documentation, that's not very obvious.</font></div><div class=""><font color="#454545" face="Helvetica Neue" class=""><br class=""></font></div><div class=""><font color="#454545" face="Helvetica Neue" class="">Maybe another approach would be to make </font><span class="" style="color: rgb(69, 69, 69); font-family: 'Helvetica Neue';">removeLast() throw an exception if the collection is empty?</span></div><div class=""><font color="#454545" face="Helvetica Neue" class="">That way you can use "try" to safely remove the last item of a collection.</font></div><div class=""><br class=""></div><div class=""><font color="#454545" face="Helvetica Neue" class="">The reasoning behind this is that right now, to safely use removeLast(), you pretty much have to do something like this:</font></div><div class=""><font color="#454545" face="Helvetica Neue" class="">if !collection.isEmpty {</font></div><div class=""><font color="#454545" face="Helvetica Neue" class=""><span class="Apple-tab-span" style="white-space: pre;"> </span></font><span class="" style="color: rgb(69, 69, 69); font-family: 'Helvetica Neue';">collection.removeLast()</span></div><div class=""><font color="#454545" face="Helvetica Neue" class="">}</font></div><div class=""><font color="#454545" face="Helvetica Neue" class=""><br class=""></font></div><div class=""><font color="#454545" face="Helvetica Neue" class="">Having this method throw would allow to change the above to:</font></div><div class=""><font color="#454545" face="Helvetica Neue" class="">try </font><span class="" style="color: rgb(69, 69, 69); font-family: 'Helvetica Neue';">collection.removeLast()</span></div><div class=""><div class=""><font color="#454545" face="Helvetica Neue" class=""><br class=""></font></div><div class=""><font color="#454545" face="Helvetica Neue" class="">– Louis D'hauwe</font></div><div class=""><font color="#454545" face="Helvetica Neue" class=""><br class=""></font></div></div><div><blockquote type="cite" class=""><div class="">On 17 Oct 2016, at 22:52, Max Moiseev <<a href="mailto:moiseev@apple.com" class="">moiseev@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="">You can use popLast, that does exactly that: <a href="https://github.com/apple/swift/blob/master/stdlib/public/core/BidirectionalCollection.swift#L213" class="">https://github.com/apple/swift/blob/master/stdlib/public/core/BidirectionalCollection.swift#L213</a><div class=""><br class=""></div><div class="">Max</div><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Oct 17, 2016, at 1:14 PM, Louis D'hauwe 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=""><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">Regarding the removeLast() function on Collection:</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69); min-height: 14px;" class=""><br class=""></div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""><a href="https://github.com/apple/swift/blob/c3b7709a7c4789f1ad7249d357f69509fb8be731/stdlib/public/core/BidirectionalCollection.swift#L228" class="">The current implementation</a> is:<br class="">
@discardableResult</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">public mutating func removeLast() -> Iterator.Element {</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""> <span class="Apple-tab-span" style="white-space:pre"> </span>let element = last!</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>self = self[startIndex..<index(before: endIndex)]</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>return element</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">}</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69); min-height: 14px;" class=""><br class=""></div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">This makes it so that if you call <b class="">removeLast() </b>on an empty collection you get a fatal error.</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">("fatal error: can't remove last element from an empty collection")</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69); min-height: 14px;" class=""><br class=""></div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""><a href="https://github.com/apple/swift/blob/c3b7709a7c4789f1ad7249d357f69509fb8be731/stdlib/public/core/BidirectionalCollection.swift#L220" class="">The documentation for <b class="">removeLast()</b></a> even has this noted:<br class="">
"The collection must not be empty.".</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69); min-height: 14px;" class=""><br class=""></div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">Surely you could just remove the explicit unwrapping of 'last' and add a guard statement? </div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69); min-height: 14px;" class=""><br class=""></div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">As such:</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">@discardableResult</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">public mutating func removeLast() -> Iterator.Element? {</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""> <span class="Apple-tab-span" style="white-space:pre"> </span>guard let element = last else {</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>return nil</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>self = self[startIndex..<index(before: endIndex)]</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>return element</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">}</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69); min-height: 14px;" class=""><br class=""></div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">It sure seems more "Swifty" to alert at compile time that removing the last item of a collection might fail, and make it return nil as a result.</div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69); min-height: 14px;" class=""><br class=""></div><div style="margin: 0px; line-height: normal; font-family: 'Helvetica Neue'; color: rgb(69, 69, 69);" class="">– Louis D'hauwe</div><div class=""><br class=""></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=""><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></div></blockquote></div><br class=""></body></html>