[swift-evolution] History and future of Swift's parentheses

Gwendal Roué gwendal.roue at gmail.com
Fri Jun 9 10:18:16 CDT 2017

> Le 9 juin 2017 à 17:12, Gor Gyolchanyan via swift-evolution <swift-evolution at swift.org> a écrit :
>> So I wonder if any of you have had any thoughts about what Swift's parentheses-related future (or evolutionary baggage) will be?
> I really wish swift used the concept of tuples **exclusively** for all purposes that involve parentheses, as well as dividing tuples into two categories:
> - Bare tuples, which do not have labels.
> - Rich tuples, which do.
> As a consequence, here's a list of statements that would become true:
> - All functions take exactly one parameter, which is a tuple.
> - All closures (a.k.a. function pointers) take exactly one parameter, which is a bare tuple.
> - All functions return exactly one parameter, which is a tuple.
> - Pattern matching is done on a single bare tuple using a single bare tuple pattern.
> The currently ongoing proposal to make a single-element tuple auto-flatten would work extremely well with this idea, by making all these changes completely backward-compatible.

If I have well understood, Swift has evolved away from this.

If what you describe were true, added to the fact that there is no such thing as a one-element tuple in the language, then (A,B) -> C and ((A, B)) -> C could not be distinguished, for the simple reason that ((A, B)) -> C could not be defined.

For ((A, B)) -> C to be defined, we'd need a function that takes exactly one parameter, which is a tuple (your idea), whose single element is a tuple (oops, there is no single-valued tuples).

No opinion here, just they way I have understood recent Swift history.

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