Generic type in a protocol

[Danny]

Keep reading.

What's the state of higher kind types?

Parameterized associate types are how ML languages model higher kinded types0, but they're free functions (or functions in a module). I think the equivalent would be making a separate mapper type: protocol Mappable { associatedtype Container<A> static func map<Element, Result>( _ base: Container<Element>, transform: (Element) -> Result ) -> Container<Result> } struct ArrayMapper: Mappable { typealias Container<A> = [A] static func map<Element, Result>( _ base: [Element],…