in section 1.1, it is emphasized that the actors are library extensions in Scala, as opposed to, these constructs being ''built into the language'' in Erlang.
what does this mean?
As far as I understand, to me it feels like that the access to the definitions of what actors are, is hidden in Erlang and is with the creators of the language, while in Scala, the sources, or the definitions of actors, are available to the users.
On a larger level, much emphasis has been laid in the first chapter that for the purpose of scalability, many things in Scala are provided as library extensions as compared to other languages which try to implement those things as something which is built into the language. I'm not able to understand this difference.
Taking this even further, these 4 points from page 52 of the pdf book (2nd ed) are still grey to me.
But any language that attempted to implement all of these abstractions at the same time would simply become too big to be manageable.
What’s more, even if such a language were to exist, some applications would surely benefit from other numberlike types that were not supplied.
So the approach of attempting to provide everything in one language doesn’t scale very well.
Instead, Scala allows users to grow and adapt the language in the directions they need by defining easy-to-use libraries that feel like native language support.