<div dir="ltr">To elaborate, the reason I like this is that I think it fits with Swift's general pattern (no pun intended) of extending familiar C syntactic forms to work with functional features. C's enums become Algebraic Datatypes; C's switch statements become pattern-matching statements; C's if and for and while statements are also updated with pattern-matching abilities.<div><br></div><div>The ternary operator is C's answer to the "if-as-an-expression" question. So why can't a modified version be our answer to the "pattern-matching-as-an-expression" question?</div><div><br></div><div>It also has the advantage of being more explicit than the original ternary operator -- having to label the true: and false: cases makes it clearer what you're trying to achieve.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Dec 6, 2015 at 12:02 PM, Alex Lew <span dir="ltr"><<a href="mailto:alexl.mail+swift@gmail.com" target="_blank">alexl.mail+swift@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">What if we left the if { ...} else { ... } syntax alone (as a statement), and updated the ternary expression to be a more general pattern matching expression (closer to "switch")? Something like<div><br></div><div>let x = condition ?</div><div> true: "Hello"</div><div> false: "Goodbye"</div><div><br></div><div>let x = optionalValue ?</div><div> .Some(let unwrapped): "Hello, \(unwrapped)"</div><div> .None: "To Whom It May Concern"</div><div><br></div><div>let myFavoriteColor = yourFavoriteColor ?</div><div> .Blue: .Red</div><div> .Green: .Blue</div><div> .Red: .Green</div><div><br></div><div>let quadrant = (x, y) ?</div><div> let (x, y) where x < 50 && y < 50: "top left"</div><div> let (x, y) where x < 50 && y > 50: "bottom left"</div><div> let (x, y) where x > 50 && y < 50: "top right"</div><div> default: "bottom right"</div><div><br></div><div>The colon comes from the fact that this is sort of a light-weight expression-based "switch" statement, where each branch can only contain an expression, not a series of statements.</div><div><br></div><div>This is very similar to pattern matching expressions in languages like Haskell, ML, and Coq.</div></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Dec 6, 2015 at 11:25 AM, Thorsten Seitz <span dir="ltr"><<a href="mailto:thorsten.seitz@web.de" target="_blank">thorsten.seitz@web.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div><span><blockquote type="cite"><div>Am 06.12.2015 um 01:28 schrieb Alex Lew via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>:</div><br><div><div dir="ltr">I don't think you can just get rid of the if statement in favor of an expression. You still want to be able to do this:<div><br></div><div>if (condition) {</div><div> funcWithSideEffectsThatReturnsInt()</div><div>} else {</div><div> funcWithSideEffectsThatReturnsString()</div><div>}</div><div><br></div><div>but that's not a valid expression (what is its type?).</div></div></div></blockquote><div><br></div></span><div>That would actually be no problem if Swift’s type system would have union types (Ceylon has union and intersection types which are quite awesome and enable lots of nice things quite naturally, see <a href="http://ceylon-lang.org/documentation/1.2/tour/types/" target="_blank">http://ceylon-lang.org/documentation/1.2/tour/types/</a>).</div><div><br></div><div>In that case the type of such an expression would just be the union of both types, which is written <font face="Courier">Int | String</font> in Ceylon.</div><span><font color="#888888"><div><br></div><div>-Thorsten</div></font></span></div><br></div></blockquote></div><br></div>
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