Yes, the threads are green threads: only one can run at a time. There's also an Async framework in Jane Street's Core library and there's LWT.
My understanding is that GC is hard with multithread, particularly in a functional language where it's going to do some heavy lifting and needs to be very performant.
My understanding is that GC is hard with multithread, particularly in a functional language where it's going to do some heavy lifting and needs to be very performant.