[swift-evolution] ternary operator ?: suggestion

[J. Cheyo Jimenez]

There are a couple of languages that use then inside their switches.
http://rigaux.org/language-study/syntax-across-languages.html#CntrFlowMltSlcSwt

I like using only one then in the switch to signal to the parser that this
is a switch expression

The only issue I see is that the colon in the switch is used in the same
way as the current ternary expression.

Personally I don't think that a switch expression is all that useful since
being a multiline statement actually helps the readability.

var result:Int = {if bool {return 1} else if bool {return 2} else {return 3
}}()

VS

var result = if bool then 1 else if bool then 2 else 3

On Sat, Dec 12, 2015 at 11:15 AM, Al Skipp via swift-evolution <
swift-evolution at swift.org> wrote:

> On 12 Dec 2015, at 14:48, Paul Ossenbruggen <possen at gmail.com> wrote:
>
> 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:
>
> let v = switch val then .Red: 1, .Green: 2, .Blue: 3
>
> It is definitely nice in it’s compactness which is a big plus.
>
> Another possibility, because “switch" does not need to resolve the
> syntactic ambiguity, but then we lose the “then” always meaning an
> expression consistency.
>
> let v = switch val case .Red: 1, case .Green: 2, case .Blue: 3
>
> 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”
>
>
> Would the cases need to be comma separated? Would a new line make more
> sense instead?
>
> Currently this is possible:
>
> enum Col { case Red, Green, Blue }
>
> let c = Col.Blue
>
> let x: Int = {
>   switch c {
>   case .Red: return 1
>   case .Green: return 2
>   case .Blue: return 3
>   }
> }()
>
> It works, but there are several things I don’t like:
> - the switch statement must be wrapped in a closure which is invoked at
> the end.
> - the type of ‘x’ needs to be given
> - each case requires a return statement
>
> Here’s a proposal for a switch expression:
>
> let y = switch c then {
>   .Red: 1
>   .Green: 2
>   .Blue: 3
> }
>
> I think the braces are probably needed in the switch expression, also the
> ‘then’ keyword’ does look a bit peculiar. Any other ideas on how to support
> both switch statements and expressions?
>
> Al
>
>
>
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>
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