How to update this code to use parameter packs?

[Dmitriy_Ignatyev]

@StevenSorial

@dynamicMemberLookup
class CN<each L: P>: A {
  subscript(dynamicMember keyPath: KeyPath<each L, A>) -> A { // <---❓
    return each L(source: self)[keyPath: keyPath] // <---❓
  }
}

Currently variadic packs allows to create functions with several arguments of related types. In your case I think it is not supposed that subscript can take several key paths like subscript(dynamicMember keyPath1: KeyPath<L1, A>, keyPath2: KeyPath<L2, A>), keyPath3: ...

Instead several subscript overloads are needed, something like:

class CN<each L: P>: A {
  repeat
  subscript(dynamicMember keyPath: KeyPath<each L, A>) -> A {
    return each L(source: self)[keyPath: keyPath]
  }
}

Similar topic has also appeared in another discussion, here is @scanon answer:

Add splitMap function to Swift standard library

This is a thing that we want to be possible with variadics (and I would probably not add it to the standard library proper until it could be done in such a manner), so this points at variadics features or documentation that's missing. Can you either file a bug report or make a separate thread focused on this? In the meantime, this might make sense for algorithms. In some sense it's "just" a reduce, but half of algorithms is "just a reduce", so I think I'm OK with that. @nnnnnnnn? (There's als…

I've created a thread, though it should be named better to generalize both cases:

Generic parameter pack expansion only for return value

This thread is created on request of @scanon (Add splitMap function to Swift standard library - #10 by scanon) The original intent is to address cases where single input Type is needed to be transformed into multiple Types, like this: extension Sequence { // curent imp: func splitMap<T1, T2, E: Error>(_ transform: (Element) throws(E) -> Either<T1, T2>) rethrows -> ([T1], [T2]) // we are currently limited by 2 generic Types // what we need is something like: func splitMap<each T, E: Error>(…