On 15 Sep 2017, at 21:35, Vladimir.S via swift-users <swift-users@swift.org> wrote:
> … for me it is very strange decision to disallow a method because it is > 'expensive'. That’s pretty normal for Swift standard library protocols, which define not just the behaviour of the routine but expected performance. `popFirst()` is expected to be O(1) and that’s not possible with `Array`. The rationale behind this decision is, I believe, related to generic algorithms. If I write generic code that uses `popFirst()`, I can only guarantee the complexity of my code if I can rely on `popFirst()` being O(1). If someone implements `popFirst()` as O(n), my generic algorithm might go from O(n^2) to O(n^3), which is quite a change. On 16 Sep 2017, at 01:44, Rick Mann via swift-users <swift-users@swift.org> wrote: > Is the compiler looking at the name "pop" and adding additional constraints > (and then spewing a bogus error message)? I’m not sure what’s going on here mechanically but, yes, the error message is bogus. This is exactly what SR-5515 is talking about. If I were in your shoes I’d call this method something other than `popFirst()`. This falls under my standard “if you change the semantics, change the name” rule. Your implementation of `popFirst()` doesn’t conform to the semantics of `popFirst()` — it’s O(n) because `removeFirst()` is O(n) — and thus you want to avoid calling it `popFirst()`. Share and Enjoy -- Quinn "The Eskimo!" <http://www.apple.com/developer/> Apple Developer Relations, Developer Technical Support, Core OS/Hardware _______________________________________________ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
