[swift-evolution] Proposal: Always flatten the single element tuple

[Susan Cheng]

that makes sense to me ;P

2017-06-08 12:07 GMT+08:00 Gwendal Roué <gwendal.roue at gmail.com>:

> Le 8 juin 2017 à 05:15, Susan Cheng via swift-evolution <
> swift-evolution at swift.org> a écrit :
>
> Just a thought
>
> if parentheses is important, why the tuples are not?
>
> var tuple1: (Int, Int) = (0, 0)
> var tuple2: ((((Int, Int)))) = (0, 0)
>
> type(of: tuple1) == type(of: tuple2)    // true
>
> var void: ((((((())))))) = ()
>
> type(of: void) == type(of: Void())  // true
>
>
> I think is is because Swift doesn't have tuples with a single value: those
> parenthesis are just parenthesis around an expression:
>
>     let a = 1 + 2
>     let b = (1 + 2)
>     let c = (1 + 2) * 3
>     let d = ((1 + 2)) * 3
>
> Many languages behave like that, Swift is no exception.
>
> It also allows some fancy/legacy/foreign programming styles :-)
>
>     // C-style if
>     if (a && b) {
>         ...
>     }
>     // "return function"
>     return(a && b)
>
> Languages that have single-valued tuples need a special syntax so that
> they are distinguished from parenthesised expressions. In Python, this is a
> trailing comma:
>
>     1    # 1
>     (1)  # 1
>     (1,) # (1,)
>
> Swift currently disallows trailing commas inside parenthesis.
>
> Gwendal
>
>
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