Parenthesizes
Remove extra asInstanceOf
Use Scala's collection libraries instead of Java's them
A little refactoring
A little refactoring
A little refactoring.  Use Scala collections
A little refactoring
Remove unnecessary paranthesis
Fix some error while executing Onion's program
Fix some bugs
Fix: Bug adding null
Fix by lazy modifier
Remove dependency of java.util.List and java.util.ArrayList
Refactor AST.toString
Introduce scala.Some into JavaCC grammer file to avoid null
Use Scala 2.11.3 and don't test except for oraclejdk7