I have to say, I don't really "X is just a library" arguments. Is it a way to say "language L1 is so much more expressive than language L2"?

One of the nice things about Erlang is that the actor model isn't just a library.

EDIT: actors -> the actor model

Naturally. Actor model as a library is a design pattern. Design patterns are merely patches for missing language features - for better or worth.

> Actor model as a library is a design pattern. Design patterns are merely patches for missing language features

In the sense in which it is accurate to say that "design patterns are merely patches for missing language features" -- that is, design patterns that are applied as code templates -- anything that can be implemented once as a library is not a design pattern in the language where that is possible.

Do you know a good actor library for another language? I'd be very interested to hear of one for Python, because I still have to use it sometimes.

Io comes with Actors built-in - http://iolanguage.org/scm/io/docs/IoGuide.html#Concurrency-A...

Perl has an experimental Actor model library threads::lite - https://metacpan.org/pod/threads::lite

There are multiple for .NET: http://stackoverflow.com/questions/2186222/any-good-implemen...

For distributed scenarios NServiceBus is a good option although it's a bit different kind of model.

For Java: http://blog.paralleluniverse.co/post/49445260575/quasar-puls...

Yes, you can use Akka from Java. Just to show that you don't need something like Scala to implement an actor system.

I don't see any Java examples on that page, just Clojure.

There's always pulsar: https://pypi.python.org/pypi/pulsar

I confess I haven't used it before though...why use pulsar when I can get away with using akka?

Celluloid is great for Ruby, I'm not sure what Python has.