[swift-evolution] [Pitch] Make `default` function parameter values more transparent

[Erica Sadun]

I'm not sure what enhancing defaults would look like, especially for protocols. Are you suggesting if there's a protocol like:

protocol A {
   func requiredFunction(a, b, c) -> T
}

that you could then extend 

extension A {
    func requiredFunction(a, b = somedefault, c) -> T;
}

as a declaration without an implementation?

-- E

> On Jun 13, 2016, at 2:17 AM, Haravikk via swift-evolution <swift-evolution at swift.org> wrote:
> 
> As Charlie says the default value may not actually be public.
> 
> There was a thread a while ago about allowing defaults to be defined in protocols, but I don’t think it ever got made into a proposal; this would be useful however in cases where you want a consistent, known default. Either that or you need the option of declaring a default value as public perhaps?
> 
>> On 11 Jun 2016, at 14:35, Adrian Zubarev via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> I just installed the current Swift 3 snapshot to play around with it (last from may crashed my Xcode all the time).
>> 
>> I wanted to re-build a small project with (currently implemented) Swift 3 changes. Basically I had to look up on GitHub what the default value for deinitialize(count:) function was for UnsafeMutablePointer, just because Xcode and the docs can’t tell me that:
>> 
>> /// De-initialize the `count` `Pointee`s starting at `self`, returning
>> /// their memory to an uninitialized state.
>> ///
>> /// - Precondition: The `Pointee`s at `self..<self + count` are
>> ///   initialized.
>> ///
>> /// - Postcondition: The memory is uninitialized.
>> public func deinitialize(count: Int = default)
>> To cut it short:
>> 
>> Could we make default function parameter values more transparent in Swift 3?
>> Why are default parameter values translated to default rather than the actual value?
>> Can we make this independent from docs?

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