[swift-evolution] ternary operator ?: suggestion

Sean Heber sean at fifthace.com
Tue Jan 5 10:23:25 CST 2016

> On Jan 5, 2016, at 12:29 AM, Thorsten Seitz via swift-evolution <swift-evolution at swift.org> wrote:
> I once suggested the following ternary like switch:
> let x = color ?
>         case .Red: 0xFF0000
>   	case .Green: 0x00FF00
>         case .Blue: 0x0000FF 
>         default: 0xFFFFFF

This is my favorite and addresses the sort of situations I’ve run into where using a switch statement seems unnecessarily bulky. I’d like to see this as a proposal because it’d be a very useful construct on its own.

Using “else” would be maybe a little odd when paired with cases, but it also doesn’t look bad and, I think, could be argued that it makes sense in the context of an expression:

let x = color ?
  case .Red: 0xFF0000
  case .Green: 0x00FF00
  case .Blue: 0x0000FF
  else: 0xFFFFFF

Then you could say this when using a boolean:

let x = something ? case true: thing() else: otherThing()

And maybe allow a special case for boolean where you can leave off the “case true:” part:

let x = something ? thing() else: otherThing()

And then you could more or less replace ternary with this new construct that can do even more while looking very similar and still being pretty terse and the addition of “else” in there makes the entire expression stand out a bit more than traditional ternary expressions which, I think, addresses one of the complaints there.


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