diff --git a/ParseMe.scala b/ParseMe.scala
index bfe3dfc96cbd7ed37879acb25179d4cb1a270c61..51d34280866d171c2af4c26bd084d515f9028f98 100644
--- a/ParseMe.scala
+++ b/ParseMe.scala
@@ -9,4 +9,8 @@ object ParseMe {
   def fromSet(i: Set[Set[Boolean]]) : Int = {
     5
   }
+
+  def emptySet(n: Tree) : Tree = {
+    Leaf()
+  }
 }
diff --git a/src/purescala/Trees.scala b/src/purescala/Trees.scala
index 288c2eb73ceaf35ee3145a005ce73d6505c2b1a2..ace8d8e01f5b0102c7dbbd2513e355e6040ea94d 100644
--- a/src/purescala/Trees.scala
+++ b/src/purescala/Trees.scala
@@ -73,6 +73,9 @@ object Trees {
 
   case class IntLiteral(value: Int) extends Literal[Int] 
   case class BooleanLiteral(value: Boolean) extends Literal[Boolean] 
+  case class StringLiteral(value: String) extends Literal[String]
+
+  case class CaseClass(classDef: CaseClassDef, args: Seq[Expr]) extends Expr
 
   /* Arithmetic */
   case class Plus(lhs: Expr, rhs: Expr) extends Expr