You're from Parallel Universe? I've played with the idea of a programming language, looking for an async layer that supports Scala style Future[T]s. Possible with Quasar?

Not entirely sure what you mean by "the idea of a programming language". Scala-like futures are already in the JDK as CompletableFuture. Quasar is something different (and, I believe, better): it provides true fibers (aka lightweight threads), just like Erlang or Go.

I've meant playing with the idea for a programming language.

With Future I've meant would it be easy to put a Future based API which I like b/c of composiblity on top of Quasar, e.g. on top of fibers.

(Futures are just an API to concurrency not concurrency itself that can sit on actors, forkjoin, ...)

Then sure. But check out this talk/blog post, which explains why such monadic futures are not a good way to compose asynchronous code: http://blog.paralleluniverse.co/2015/08/07/scoped-continuati...