JDK

JDK, the Java Development Kit, version 1.6 or 1.7

Sbt

Sbt, a build tool for Scala, version 0.12.0

macOS

Install it using Macports:

$ sudo port install sbt

Verify it works:

$ sbt -h
Getting org.scala-sbt sbt 0.13.0 ...

Scala IDE for Eclipse

The Scala IDE for Eclipse

Scala worksheet