akka-core

Good point. Though implicits I feel are so much simpler than many people fear. From a Ruby perspective: Just think of them as operating similarly to Refinements, except not completely insane because there is no global scope at compilation. You only have to worry about your own package, imports and inheritance. Tracking down an implicit generally takes all of 10 seconds, and never more than a few minutes. Even moderately brain-bendy ones like akka.patterns.ask (where does the implicit "?" come from? "ask" is actually an implicit conversion to a class that defines it: https://github.com/akka/akka/blob/master/akka-actor/src/main...).

Akka actors have a very similar feature, same name. It doesn't swap identities though. It's actually pretty cool if you think of it as a way to track state without having a mutable variable. One example is this implementation of the dining philosophers problem: https://github.com/akka/akka/blob/master/akka-samples/akka-s... You can also use "unbecome" and effectively treat an actor's behavior as a stack, popping and pushing receive functions. One cool trick is to bind a value to your receive function: def receive(foo: Foo): Receive = { ... } Then you can bind immutable data to a given receive function but think of it as mutable by replacing the current receive function with become().