I recently spend some days playing with differentiable programming in Swift on Linux:

* as you said, auto-diff is in a branch or the Google fork of the project * the only pre-built images are for Ubuntu 18.04 * on Linux, the REPL seems to somewhat broken * many libraries are assuming OSX or iOS

I don't feel a lot of hope for adoption of Swift on Linux. Apple obviously is not working on that (fair, they have no reason to do so) and the Swift community also has no focus on Linux, since ... they are in the Apple ecosystem. Meanwhile, the Open Source community is much more interested in Rust than Swift.

For the differentiable programming - this is what got me excited, but after trying, I was a bit underwhelmed. Not that it isn't great technology, its just not figured out yet. I tried to come up with a use case outside of ML and the one I tried wasn't really applicable.

I do feel however that someone will come up with something and that it will have quite some impact.

Apple I believe has a reason to work on Swift for Linux, and that reason is their considerable cloud infrastructure and various backend services.

I’m sure being able to share domain specific Swift code between client apps and backend would be pretty high on their list of wants.

Also, little clues like the way Xcode generates SwiftPM packages in a Linux-ready fashion out of the box shows that they care at least a bit.

Having a lot of interest in the programming languages, my opinion is that Swift is a damn good one. It’s very high level, supports FP deep enough, has a great type system (that is getting better with every release), great OOP support, native performance characteristics and it still lets you get to a really low level when you need it.

I also like how they took great ideas from Haskell, Scala, Smalltalk, C# and others. I code daily in Scala and Swift, previously had done Erlang, Clojure, Common LISP, TypeScript, Ruby, Python, Haskell, OCaml, Java, PHP, C, Smalltalk and some others. In this list, Swift is now almost at the top.

They need to get Higher-Kinded Types and then it’s going to win the world (just kidding, JavaScript gets to win the world, unfortunately) :)

If Apple has intrinsic care for Swift on Linux then let it be evident in their story or direction.

SwiftNIO is a cross-platform asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. (https://github.com/apple/swift-nio)

Distributed Membership Protocol implementations in Swift: https://github.com/apple/swift-cluster-membership

Docker Official Image packaging for Swift: https://github.com/apple/swift-docker

Also, on official https://swift.org/download all releases and snapshots are automatically available for: Ubuntu 16.04, Ubuntu 18.04, Ubuntu 20.04, CentOS 7, CentOS 8, Amazon Linux 2

Official Swift Server work group is a steering team that promotes the use of Swift for developing and deploying server applications: https://swift.org/server/

Swift AWS Lambda Runtime: https://github.com/swift-server/swift-aws-lambda-runtime

Official Swift 5.3 release goals have stated a major goal of "expanding the number of platforms where Swift is available and supported, notably adding support for Windows and additional Linux distributions." (https://swift.org/blog/5-3-release-process/)