<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="">+1 for Paul and Jacob’s ideas.<div class=""><br class=""></div><div class="">I’m not a fan of the original example, because then you could just have one optional variable or constant that just cascades through your code and gives everything an inferred Optional type, and then you lose the power of optionals because the compiler doesn’t make you check for them. Here’s an example for where that could go awry:</div><div class=""><br class=""></div><div class=""><div class="">Let's say you're writing code that takes a String from user input somewhere and parses it into an Int.</div><div class=""><br class=""></div><div class=""><font face="Menlo" class="">let numCaloriesJustEaten = Int(userInputString) //Let's say </font><span style="font-family: Menlo;" class="">userInputString</span><font face="Menlo" class=""> is `two`. Type inferred as `Int?`, and would have value of nil</font></div><div class=""><font face="Menlo" class="">dict["caloricConsumption"] = numCaloriesJustEaten + (dict["caloricConsumption"] ?? 0)</font></div></div><div class=""><br class=""></div><div class="">The intention of this code would be to increment caloricConsumption by the recently-eaten calories. In Swift, this (rightfully) wouldn’t compile. If Swift operated according to the original example, then the whole expression of `<span style="font-family: Menlo;" class="">numCaloriesJustEaten + (dict["caloricConsumption"] ?? 0)</span>` would compile, and would have a value of nil at runtime.</div><div class="">This would remove the value of `<font face="Menlo" class="">dict["caloricConsumption”]</font>` because when you set a the value of a key to nil, it removes that key from the dictionary entirely. This would be a logic error that is currently caught as a compile-time error in Swift today.</div><div class=""><br class=""></div><div class="">-Robert</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Jan 28, 2016, at 2:34 AM, Jacob Bandes-Storch 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=""><div dir="ltr" class="">I've wanted this sort of thing a lot. It would also work for other functions, such as<div class=""><br class=""></div><div class=""> manager.doSomething(data: data, count: n?)</div><div class=""><br class=""></div><div class="">which is equivalent to</div><div class=""><br class=""></div><div class=""> n.map { manager.doSomething(data: data, count: $0) }</div><div class="gmail_extra"><br class=""></div><div class="gmail_extra">It might be hard to see exactly which operator/function applications such a thing applies to, if used in the context of a complex expression.</div><div class="gmail_extra"><br clear="all" class=""><div class=""><div class="gmail_signature"><div dir="ltr" class=""><div class="">Jacob<br class=""></div></div></div></div>
<br class=""><div class="gmail_quote">On Wed, Jan 27, 2016 at 9:50 PM, Paul Ossenbruggen via swift-evolution <span dir="ltr" class=""><<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class="">Maybe something like this?<div class=""><br class=""></div><div class=""><span class=""><div class=""><div style="margin:0px;line-height:normal;font-family:Menlo" class=""><span style="color:#bb2ca2" class="">let</span> n : <span style="color:#703daa" class="">Int</span>? = <span style="color:#272ad8" class="">5</span></div><div class=""><span style="color:#272ad8" class=""><br class=""></span></div></div></span><div class=""><div style="margin:0px;line-height:normal;font-family:Menlo" class=""><span style="color:#bb2ca2" class="">let</span> r = <span style="color:#4f8187" class="">n</span>? + <span style="color:#272ad8" class="">5</span></div><div class=""><span style="color:#272ad8" class=""><br class=""></span></div><div class=""><span style="color:#272ad8" class=""><br class=""></span></div></div><div class=""><div class="h5"><div class=""><blockquote type="cite" class=""><div class="">On Jan 27, 2016, at 9:46 PM, Thorsten Seitz <<a href="mailto:tseitz42@icloud.com" target="_blank" class="">tseitz42@icloud.com</a>> wrote:</div><br class=""><div class=""><div dir="auto" class=""><div class=""></div><div class="">Too much hidden magic IMO. This would mean loosing the benefits of optionals, i.e. making explicit where optional cases occur and that handling the missing case has to be considered. </div><div class=""><br class=""></div><div class="">-Thorsten </div><div class=""><br class="">Am 28.01.2016 um 06:30 schrieb Craig Cruden via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>>:<br class=""><br class=""></div><blockquote type="cite" class=""><div class="">Yes<br class=""><div class=""><blockquote type="cite" class=""><div class="">On 2016-01-28, at 12:28:40, Paul Ossenbruggen <<a href="mailto:possen@gmail.com" target="_blank" class="">possen@gmail.com</a>> wrote:</div><br class=""><div class=""><div style="word-wrap:break-word" class="">Trying to see if I got this. So the type of r would be Int? at the end of this? And if n were nil then r would be nil? Otherwise it r is 10?<div class=""><br class=""></div><div class=""><div class=""><br class=""></div><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jan 27, 2016, at 9:19 PM, Craig Cruden via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>> wrote:</div><br class=""><div class=""><div style="word-wrap:break-word" class="">Swift currently encourages a lot of conditional code - especially when it comes to optionals. In most cases when you are computing etc. on an Optional you would expect that you would want an optional result and things to be able to use optionals. <div class=""><br class=""></div><div class="">In another language I generally just `map` one optional to another - which may not be the most readable code to some not use to optionals. </div><div class=""><br class=""></div><div class="">I was wondering if maybe an expression is not available that it would rewrite the syntax to map from one to another value. </div><div class=""><br class=""></div><div class="">So things like:</div><div class=""><br class=""></div><div class="">let n : Int? = 5</div><div class=""><br class=""></div><div class="">let r = n + 5</div><div class=""><br class=""></div><div class="">would actually compile as </div><div class=""><br class=""></div><div class="">let r = n.map <span style="font-family:Menlo;font-size:11px" class="">{$0 + </span><span style="font-family:Menlo;font-size:11px;color:rgb(39,42,216)" class="">5</span><span style="font-family:Menlo;font-size:11px" class="">}</span></div></div>_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br class=""></div></blockquote></div><br class=""></div></div></div></div></blockquote></div><br class=""></div></blockquote><blockquote type="cite" class=""><div class=""><span class="">_______________________________________________</span><br class=""><span class="">swift-evolution mailing list</span><br class=""><span class=""><a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a></span><br class=""><span class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a></span><br class=""></div></blockquote></div></div></blockquote></div><br class=""></div></div></div></div><br class="">_______________________________________________<br class="">
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