protocol definition question

Hello everyone!

My first mail on the list. That means I can't reply directly to the mail I found in the archive.

In addition to what Kevin already suggested here [swift-users] protocol definition question there is another more generic solution to circumvent the problem that you have to specify a concrete type for the array element.
You could use a second associated type in the protocol definition.

This is how it could look like:

protocol RawBits {
     associatedtype RawElement: FixedWidthInteger
     associatedtype RawValue = RawElement
     var rawValue: RawValue { get set }

extension RawBits where RawElement: UnsignedInteger, RawValue == Array<RawElement> {
     func testArray() {
         print("RawElement: \(RawElement.self) RawValue: \(RawValue.self)")

extension RawBits where RawElement: UnsignedInteger, RawValue == RawElement {
     func testUnsigned() {
         print("RawElement: \(RawElement.self) RawValue: \(RawValue.self)")

struct RBits<RawElement: FixedWidthInteger>: RawBits {
     var rawValue: RawValue

struct RBitsX<RawElement: FixedWidthInteger>: RawBits {
     var rawValue: [RawElement]

var rb = RBits(rawValue: 42 as UInt32)
rb.testUnsigned() // RawElement: UInt32 RawValue: UInt32

var rbx = RBitsX(rawValue: [1 as UInt8, 2, 3])
rbx.testArray() // RawElement: UInt8 RawValue: Array<UInt8>