iOS Does "_" in Swift 3 work on 1st only or all params?

[1458279]

https://www.hackingwithswift.com/swift3

I'm watching some Swift 3 videos and blogs and noticed this new underscore option.

Seems that if you use the underscore in front of a parameter, you don't need to have a named parameter.

func sendMessage(_ message: String, to recipient: String, shouting: Bool) {
    var message = "\(message), \(recipient):"
    if shouting {
        message = message.uppercaseString
    }
    print(message)
}

sendMessage("see you at the Bash", to: "Morgan", shouting: false)

@19:30

I don't have Swift 3 yet so I can't test everything.

Q. what happens if you put the underscore under each parameter?

Does this make it so you can have no parameter names on all of the parameters or is it just the 1st parameter?

 

[1458279]

Watching more of the video, I see @ 23:20, this:
func filterInts(_ numbers: [int], _ includeNumber: type) -> [Int] {...}

So wouldn't that mean that the underscore can be used on any parameter?

 

[eventailapp]

Yes it can. In a Swift 3 playground this is legal:

func f(_ a: Int, _ b: Int) {
  print("\(a) \(b)")
}

f(1, 2)

 

[1458279]

Ok, this looks like it's not a Swift 3 thing, I'm running Swift 2 and just ran this from another tutorial

func adderInt(x: Int, _ y: Int) -> Int {
    return x + y
}

let intSum = adderInt(1, 2)

BTW, if anyone wants a PDF of that lesson from WWDC (404 getting started with Swift 2016) here's a link:
http://devstreaming.apple.com/video...16mdej/404/404_getting_started_with_swift.pdf