Yet another programming language I want to take a look at: Scala.
It seems to be fully compatible with Java too as well as having many features similar to Groovy (see my post on groovy).
One of the thing though that seems really interesting is the concurrent programming features as shown at this place. I still need to try that though. I also want to know in which way it differs from Message Passing Interfaces (actually I think it is kind of like MPI).
It does not seem to be as developped as Groovy. So I think I'll stick with learning Groovy.
