[swift-evolution] array splatting for variadic parameters

[Cao, Jiannan]

What happened with this proposal? This looks easy to implement.

func sumOf(numbers: Int...) -> Int {
      ...
  }
typealias Function = [Int] -> Int
let sumOfArray = unsafeBitCast(sumOf, Function.self)
sumOfArray([1, 2, 3])

> Hello everyone.
> 
> I understand that topic has already been discussed in the past, but I failed to get any information on its current state of affairs.
> 
> I guess the subject of this mail is explicit, but to make sure I’m clear, here's a small snippet that illustrates the problem:
> 
> func f(args: Int…) {
>   // Some implementation ...
> }
> // Now it's impossible to call f without explicitly naming its parameters.
> 
> For many use-cases, this problem can be solved by overloading f so that it explicitly accepts an array.
> 
> func f(_ args: [Int]) {
>   // Some implementation ...
> }
> 
> func f(_ args: Int…) {
>   f(args)
> }
> 
> Some people also advocate (myself generally included) that one should prefer the signature explicitly marking args as an array, as the syntactic overhead of wrapping the arguments with “[]” when calling f is arguably bearable. However, in some other situations, this approach might not be applicable. For instance, one may simply not be able to modify the original function. Another use-case may be a function that should forward its own variadic parameters.
> 
> In a variety of other languages, there exists a way to do this. For instance, Python can “unpack” (or splat) a list into function arguments by prefixing it with *:
> 
> def f(*args):
>   # Some implementation …
> 
> f(*[1, 2, 3]) # == f(1, 2, 3)
> 
> I was wondering if such feature could be supported by Swift, and if not, why.
> 
> Syntactically, I like the use of “…”, which would mirror function signatures:
> 
> f(…[1, 2, 3]) // == f(1, 2, 3)
> 
> Thanks.
> 
> --
> Dimitri Racordon

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