[swift-evolution] [pitch] Variadic Arguments should accept Arrays

Derrick Ho wh1pch81n at gmail.com
Sun Feb 26 21:00:29 CST 2017

Well, I have found these discussions...

It was marked as a bug <https://bugs.swift.org/browse/SR-128> and then
directed to swift evolution

@jose, the prefix operator you mention looks good, but in the past
discussions they wanted a postfix operator so that it would match the
declaration.  I think I like the postfix operator.

func foo(_ a: String...) {}

foo(["a", "b", "c"]...) //<- This looks clear.  It is turning the array
into a variadic argument.

However, that thread was closed because it wasn't "discussed" enough prior
making the pull request.

therefore, if people want it, they got to cast their vote in here by either
supporting it or opposing it.

I like my original suggestion since it is more explicit.

foo(["a", "b", "c"] as String...)

On Sun, Feb 26, 2017 at 7:59 PM Jose Cheyo Jimenez <cheyo at masters3d.com>

> On Feb 26, 2017, at 8:26 AM, Derrick Ho via swift-evolution <
> swift-evolution at swift.org> wrote:
> In swift, a variadic argument can become an array without too much effort.
> func foo(_ va: String...) {
>    let a: [String] = va
> }
> However, it seems odd to me that an array can not be converted into a
> variadic argument
> foo(["a", "b", "c"]) // <-error
> foo("a", "b", "c") // no error
> Other people have wondered about this too.
> <http://stackoverflow.com/questions/24024376/passing-an-array-to-a-function-with-variable-number-of-args-in-swift>
> According to this thread
> <https://devforums.apple.com/message/970958#970958> Doug Gregor says it
> is due to some type ambiguity. with Generics.
> If type ambiguity is the issue, Do we have the option to cast it to the
> correct type?
> foo(["a", "b", "c"] as String...) // <- error.  doesn't consider String...
> to be a type.
> I think this needs to be done with a spread operator in order to
> disambiguate.
> foo(...["a", "b", "c”]
> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator
> I like the idea. Its syntactic sugar so I am not sure how open the core
> team would be to adding it.
> What does the community think? Should we be granted some mechanism to turn
> an array into a variadic argument?
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