Comment by JonChesterfield

> Functions are first-class values...

Good

> Functions can not be sent in messages to other actors

Oh, so not first class. Mutable closures are tricky to implement though, so fair enough.

> Function objects are immutable values.

Huh. That means you can easily send a function to another actor. Can even serialise it and send it over a network. That stuff is a real pain for closures over mutable state but totally straightforward for immutable values.

That seems like a implementation limitation turning up in the language spec instead of fixing the implementation.