Scala does not follow the usual version number conventions. Scala 2 was a total re-write from Scala 1 (the compiler was ported from Java to Scala). Scala 2.8 is

Scala does not follow the usual version number conventions. Scala 2 was a total re-write from Scala 1 (the compiler was ported from Java to Scala). Scala 2.8 is a major, backwards-incompatible release with Scala 2.7. Scala 2.8.x releases will be at least backwards source-compatible. (Binary compatibility is more challenging in Scala, because of how traits work, but the Scala team is allegedly tackling this problem for 2.8.1. We'll see.)