[swift-evolution] Proposal for Passing Arrays to Variadic Functions

[Arthur Ariel Sabintsev]

Thanks for your response.

The reason this doesn't work is due to Swift's generic system as it allows
a type T to be a anything, including arrays. The example that was used to
delineate this concept to me was that of "Any...", which from within the
variadic function, could be interpreted as T or [T]. The result is
ambiguous in the current implementation, which is why some identifier
syntax needs be passed along with an array to get this to work properly.

As for the choice of operator, I'm open to suggestions. I wanted to use one
that was familiar to other developers, so I chose the one that Ruby uses.

Maybe a ~ would be better, or a keyword like @variadic?


Best,

Arthur / Sabintsev.com <http://sabintsev.com/>

On Sat, Dec 12, 2015 at 1:54 AM, Kevin Ballard via swift-evolution <
swift-evolution at swift.org> wrote:

> You can't use * as suggested, because that conflicts with * as a prefix
> operator.
>
> You could probably get away with using a trailing ... in the call, as in
>
> func foo(xs: [Int]...) {
>     bar(xs...)
> }
>
> I also wonder whether there's a reason Swift doesn't already support this.
> Maybe there's some desired future change to variadic arguments to improve
> performance (i.e. to avoid having to allocate an array) that wouldn't be
> compatible? Although I'm not sure what that would be. Maybe there's
> actually no barrier at all and it was just something that wasn't
> prioritized. It would be good to know either way.
>
> -Kevin
>
> On Fri, Dec 11, 2015, at 10:43 PM, Arthur Sabintsev via swift-evolution
> wrote:
>
> Hi,
>
> I have put together a proposal for passing arrays to variadic functions
> (along the lines of Ruby’s Splay operator).
>
> Proposal:
> https://github.com/ArtSabintsev/swift-evolution/blob/master/proposals/array-variadic-function.md
> Pull Request: https://github.com/apple/swift-evolution/pull/52
> Bug Report: https://bugs.swift.org/browse/SR-128 which led to this
> proposal
>
>
> Best,
>
> Arthur / Sabintsev.com <http://sabintsev.com>
>
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