<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div><span style="background-color: rgba(255, 255, 255, 0);">Hello,</span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);"><br></span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);">This is a repeat of an earlier post where I did not get a single response... might have fallen through the cracks...</span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);"><br></span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);"><br></span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);"><br></span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);">Earlier I posted this proposal to the Swift Evolution Mailing list. Then I looked at the NSScanner implementation in core libs and found experimental API using the return value to for returning the scanned results. See my comments on that below:</span><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">—</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">Working on a function for Foundation’s Scanner I stumbled on this LLVM crash: <a href="https://bugs.swift.org/browse/SR-3295" class="">https://bugs.swift.org/browse/SR-3295</a></span><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">This got me thinking about a workaround and I would like to prose this:</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">When importing Foundation into Swift 3, all </span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">AutoreleasingUnsafeMutablePointer<T?>?</b></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">should instead be exposed as simple:</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">inout T?</b></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">e.g.</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">open func scanString(_ string: String, into result: AutoreleasingUnsafeMutablePointer<NSString?>?) -> Bool</b></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">would become</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">open func scanString(_ string: String, into result: inout String?) -> Bool</b></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">The call would stay exactly the same for normal use cases where you specify a receiving variable:</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">var string: String?</b></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">scanString("=", into: &string)</b></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">because inout parameters require a &</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">for the use case where you don’t require a receiving parameter, a second method without result parameter would be generated:</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">open func scanString(_ string: String) -> Bool</b></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">This is necessary because you cannot specify nil or an immutable value for an inout parameter. </span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">A fixit/migration would change calls to</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">scanString(“foo", into result: nil)</b></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">into</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">scanString(“foo")</b></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">The normal call with receiving variable would stay the same. But the case without return would become more concise.</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">What do you think?</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">kind regards</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">Oliver Drobnik</span></div></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">—</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">The new experimental API does not consider the situation that one might just want to scan a token in a long string and since I know what I am scanning I don’t care about the result. For example in my scanning I would like to processed if I hit a “foo“ … </span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">The experimental API would force me to do this:</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><b class="" style="background-color: rgba(255, 255, 255, 0);">if let _ = scanString(“foo“) { }</b></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">My proposal is more elegant:</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">if scanString(“foo”) {}</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">And if you do lots and lots of these scans then performance would benefit from the compiler not having to pack the return for an autoreleasing value which would have to be released right away due to assignment to _.</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">IMHO my proposal is more in line with the spirit of the original API: 1) return Bool if the scan was successful, 2) optionally return the scanned value.</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">kind regards</span></div><div class=""><span style="background-color: rgba(255, 255, 255, 0);">Oliver Drobnik</span></div><div class=""><br class=""></div></div></body></html>