What are main changes from scala 2.8.1 to scala 2.9.1?

Question

I am working on project implemented in scala 2.8.1, want to migrate to scala 2.9.1 and use akka-actors libraries instead of standard, but didn't find good summary of main changes, here what I found:

• Changes between Scala 2.8 and Scala 2.9
• Changes in Version 2.9.0 (12-May-2011)

What are main changes from scala 2.8.1 to scala 2.9.1?
Changes that need big effort for migration.

UPDATE 1: Thanks, @VonC - Note: keep in mind some of those changes are backported in the upcoming 2.8.2: The Scala 2.8.2 distribution
UPDATE 2: Found Strange behavior of Set4 in scala 2.9.1 console

Answer 1

Parallel Collections I think is the biggest change, but in practical matters of migration, you don't have to worry too much about it. You might notice some libraries have dropped off. For example configgy is now deprecated, so check your underlying libs.

(Predef.)error is now deprecated, and there's new sys.error, so if you use a bunch of those, you'd see annoying warnings.

One major change that is not listed in the links, is around the time 2.9.0 came out the company Typesafe was formed. A part of the promise was their commitment to better binary compatibility going forward. For example, 2.9.1 is fully binary compatible with 2.9.0.1, and 2.8.2 is supposed to be compatible with 2.8.1 when it comes out.