<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="">Off Topic a little.</div><div class=""><br class=""></div>I was playing around with the equivalent case - partial functions in Scala …. <div class=""><br class=""></div><div class="">I have known for whatever reason that they would not work within the Scala `reduce` but would work in other functions…. and it bugged me as to why it would work in most but not all (I was wondering if this was some weird implementation limitation). </div><div class=""><br class=""></div><div class="">As far as I can tell, there is a little difference that prevents it. Swift reduce is probably the same as Scala’s foldLeft. I had thought Scala’s reduce is a specialized form of fold but it is not the case.</div><div class=""><br class=""></div><div class="">The difference has to be that Scala’s `reduce` takes a “commutative monoid” — and case partial functions by their very nature [conditions on accumulator or value prevent it] are not commutative in nature — or at least not guaranteed to be so. </div><div class=""><br class=""></div><div class="">Scala’s fold is either left to right, or right to left. `reduce` on the other hand provides no guarantees because it may parallelize it [I am wondering if this is something in common with the concept of big data mapReduce].</div><div class=""><br class=""></div><div class="">——</div><div class=""><br class=""></div><div class="">Paul, I will look at updating the proposal to make that clear. </div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><div><blockquote type="cite" class=""><div class="">On 2016-02-05, at 4:17:03, Paul Ossenbruggen 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 dir="auto" class=""><div class="">I haven't thought of doing it this way This is why these reviews are great. I agree with Craig that, we would not allow commas before the colon. The proposal probably should be updated to make sure that is clear. </div><div class=""><br class="">Thanks </div><div class="">- Paul </div><div class=""><br class="">Sent from my iPhone</div><div class=""><br class="">On Feb 4, 2016, at 10:31 AM, Maximilian Hünenberger <<a href="mailto:m.huenenberger@me.com" class="">m.huenenberger@me.com</a>> wrote:<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="">I definitely see the point against dictionaries but I’m afraid of the actual pattern matching in "cases".</div><div class=""><br class=""></div><div class="">match(1) {</div><div class=""> case 1, 3: 10</div><div class=""> case 2, 4: 20</div><div class=""> default: 30</div><div class="">}</div><div class=""><br class=""></div><div class="">// with "cases"</div><div class=""><br class=""></div><div class=""><div class="">match(1) { cases</div><div class=""> 1, 3: 10,</div><div class=""> 2, 4: 20,</div><div class=""> default: 30</div><div class="">}</div></div><div class=""><br class=""></div><div class="">// it is very hard to disambiguate between pattern and return value even though for the compiler it could be doable</div><div class=""><div class="">match(1) { cases</div><div class=""> 1, 3: 10, 2, 4: 20, default: 30</div><div class="">}</div></div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">There should be a more visible distinction between two "<span style="color: rgb(51, 51, 51); background-color: rgb(255, 255, 255);" class="">case-item-map" <b class=""><u class="">like</u></b> "|". But we have to consider "expression-patterns" where operators (like "|") are ambiguous.</span></div><div class=""><span style="color: rgb(51, 51, 51); background-color: rgb(255, 255, 255);" class=""><br class=""></span></div><div class=""><span style="background-color: rgb(255, 255, 255);" class=""><font color="#333333" class="">- Maximilian</font></span></div><br class=""><div class=""><blockquote type="cite" class=""><div class="">Am 04.02.2016 um 18:48 schrieb Paul Ossenbruggen <<a href="mailto:possen@gmail.com" class="">possen@gmail.com</a>>:</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="">That is a good point and I forgot about that. There are frequent cases where what I am dealing with is not hashable and it is generally a lot of work to make it hashable, including adding a heading function which if done wrong, can lead to errors. <br class=""><br class="">Sent from my iPhone</div><div class=""><br class="">On Feb 4, 2016, at 8:38 AM, Charles Constant via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class=""></div><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="">I still vote for keeping "cases"</div><br class=""><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div style="word-wrap:break-word" class=""><div class="">I see it as a replacement for dictionary literal "pattern matching":<br class=""></div><div class=""><div style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(209,47,27)" class=""><span style="" class="">[</span><span style="color:rgb(39,42,216)" class="">1</span><span style="" class=""> : </span>"one"<span style="" class="">, </span><span style="color:rgb(39,42,216)" class="">2</span><span style="" class=""> : </span>"two"<span style="" class="">, </span><span style="color:rgb(39,42,216)" class="">3</span><span style="" class=""> : </span>"three"<span style="" class="">][</span><span style="color:rgb(39,42,216)" class="">1</span><span style="" class="">] ?? </span>"undefined"</div></div><div class=""></div></div></blockquote><div class=""><br class=""></div><div class="">A dictionary needs keys that are Hashable. A dictionary produces an optional. We've discussed this, and more, earlier in the thread.</div><div class=""><br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div style="word-wrap:break-word" class=""><div class="">Even though it would be nice to have but I don’t think that I would use it frequently.</div></div></blockquote><div class=""><br class=""></div><div class="">Granted, it's a bit ugly, but given the choice, I would pick "cases" over "case case case case ..." every time.</div><div class=""><br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div style="word-wrap:break-word" class=""><div class="">In addition, to be more consistent with "case", "cases" would introduce pattern matching which doesn’t seem right with this concise syntax.</div></div></blockquote><div class=""><br class=""></div><div class="">I haven't thought this through. It just bums me out a little to replace the switch with something that still has imho unnecessary verbosity.</div><div class=""><br class=""></div><div class=""><br class=""></div></div></div></div>
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