<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="">Dropping “case” might be interesting, since it becomes a little redundant in the “switch” situation, this is one advantage of having a new keyword, but not sure this reads as well:<div class=""><br class=""></div><div class="">let v = switch val then .Red: 1, .Green: 2, .Blue: 3</div><div class=""><br class=""></div><div class="">It is definitely nice in it’s compactness which is a big plus. </div><div class=""><br class=""></div><div class="">Another possibility, because “switch" does not need to resolve the syntactic ambiguity, but then we lose the “then” always meaning an expression consistency. </div><div class=""><br class=""></div><div class="">let v = switch val case .Red: 1, case .Green: 2, case .Blue: 3</div><div class=""><br class=""></div><div class="">this might be better for switch because we don’t need to mix “then” with “switch” which historically has not been done. Question is, is it better to go with “then” as expression consistency or with slightly more compact and following the conventions out there. Personally, I am not bothered by using “then” with “switch” </div><div class=""><br class=""></div><div class=""><br class=""></div><div><blockquote type="cite" class=""><div class="">On Dec 12, 2015, at 4:03 AM, Al Skipp <<a href="mailto:al_skipp@fastmail.fm" class="">al_skipp@fastmail.fm</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 class="">If at all possible, it’d be good to avoid adding new keywords, however if the keyword ‘then’ could enable 'if expressions’ and ‘switch expressions’, I’d be fully in favour. </div><div class=""><br class=""></div><div class="">Binding to a variable using a switch statement isn’t as elegant as it could be. The ability to define a ‘let’ variable and assigning a value later in a switch statement does help somewhat, but the examples below are very clear and elegant in my opinion. (I’d even question the necessity of the repetitive keyword ‘case’, but maybe that’s a step too far?)</div><div class=""><br class=""></div><div class="">Al</div><br class=""><div class=""><blockquote type="cite" class=""><div class="">On 12 Dec 2015, at 07:15, 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 style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">So adding “then”: <div class=""><br class=""></div><div class="">let v = if condition then “A” else “B” </div><div class=""><br class=""></div><div class="">fixes that ambiguity and “then” would help differentiate an expression from a statement. I think there is value to having them separate constructs (for details see earlier comments in this thread). Also it is nice not having the braces in the expression. </div><div class=""><br class=""></div><div class="">Perhaps, similarly, “then" indicates an expression as opposed to a statement:</div><div class=""><br class=""></div><div class="">let v = switch condition then case Red: 1, case Blue: 2, case Green: 3</div><div class=""><br class=""></div><div class="">One downside is it, It may add confusion as to when to add the “then” clause as people will have to know what an expression vs statement is, but I suppose that is true with a ternary operator as well, and this reads better than a ternary operator. This also provides a good way to do single line switch expressions. </div><div class=""><br class=""></div><div class="">for multiline:</div><div class=""><br class=""></div><div class="">let v = if condition </div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>then “A” </div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>else “B"</div><div class=""><br class=""></div><div class="">let v = switch condition then </div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>case .Red: 1,</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>case .Blue: 2,</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>case .Green: 3</div><div class=""><br class=""></div><div class="">or with multiple expressions:</div><div class=""><br class=""></div><div class="">let v = switch condition then </div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>case .Red: 1,</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>case .Blue: (if shade == .Dark then 4 else 2),</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>case .Green: 3</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><div class=""><blockquote type="cite" class=""><div class=""><br class=""></div><div class="">On Dec 11, 2015, at 8:57 PM, Chris Lattner 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 class=""><blockquote type="cite" class=""><div class="">On Dec 11, 2015, at 5:36 PM, Andrey Tarantsov via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">How about:</div><div class=""><div class=""><br class="">let v = if condition then “A" else “B"<br class=""></div></div></blockquote><div class=""><br class=""></div><div class="">I don't think introducing a separate "then" keyword is a good idea, two subtly different kinds of IFs would be confusing.</div><div class=""><br class=""></div>I guess you meant:</div><div class=""><br class=""></div></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><div class="">let v = if condition { "A" } else { "B” }</div></div></blockquote></div></div></blockquote><br class=""></div><div class="">I don’t really want to wade into this discussion, but if A and B are intended to be *expressions* instead of an arbitrary sequence of statements|decls|exprs, then a more consistent syntax would be:</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>let v = if condition (A) else (b) </div><div class=""><br class=""></div><div class="">The immediate problem with that is that juxtaposition of two expressions (condition, and A [with or without parens]) will lead to immediate syntactic ambiguity.</div><div class=""><br class=""></div><div class="">-Chris</div><br class="">
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