[swift-evolution] Default implementation for protocols

[Chris Lattner]

> On Jan 30, 2016, at 4:48 PM, Howard Lovatt via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Proposal
> =======
> Allow protocols to define a default implementation, e.g.:
> 
>   protocol Complex {
>     default var re: Double = 0
>     default var im: Double = 0
>     var mag: Double { return sqrt(re * re + im * im) }
>     // ...
>   }

Hi Howard,

This is a desired feature, but a surprising amount of implementation effort blocks “just doing it”.  We hope that this will happen in Swift 3, but we’ll see how things work out with the other generics system improvements.

-Chris