[strmpnk]

I work with F# and have a lot of experience with Erlang (less so with GHC and it's lightweight green threading but I've heard good things about it).

F# inherits lots of .Net's primitives which at their core are thread pool based task scheduling with the usual optimized data structures you see from this world. While this might sound primitive, F# takes it further by providing very good functional libraries which abstract this away allowing lightweight asynchronous computations to be passed around as values (the type being Async<'a>).

Alone, this is pretty nice but it wouldn't feel as natural without computation expressions which are similar to Haskell's do-notation but with some generalizations and flexibility added in. This allows asynchronous code to look and feel first class. If you're curious I'd check out https://fsharpforfunandprofit.com/posts/concurrency-async-an... or check similar links on your search engine of choice.

Now, the story isn't complete. If you're comparing things to Erlang, there are also things like MailboxProcessor<'a> and such which allow other common patterns to be easily implemented. The type checking here is a nice bonus over some other approaches to message passing languages. The big minus of course is that it's still a traditional runtime. If you really want Erlang's isolated processes, it's hard to do that well outside of a runtime like BEAM. I also think F# could use better fault-tolerance primitives but I'm actively working on this with heavy influence from my work with Erlang.