diff --git a/.gitignore b/.gitignore
index 9086755..4407014 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,9 @@ vpl/
 *~
 \#*#
 
+# javac stuff
+*.class
+
 # javadoc stuff
 *.html
 *.js
diff --git a/tut9/src/FunctionalSet.java b/tut9/src/FunctionalSet.java
index b635fc9..73101c2 100644
--- a/tut9/src/FunctionalSet.java
+++ b/tut9/src/FunctionalSet.java
@@ -239,4 +239,16 @@ public class FunctionalSet<E> implements Set<E>
 		return res;
 	}
 	
+	public E min(Comparator<E> comp)
+	{
+		E min = null;
+		for (E elem : this)
+		{
+			if (min == null || comp.compare(min, elem) > 0) // min > elem
+				min = elem;
+		}
+		if (min == null)
+			throw new MinimumOfEmptySetException();
+		return min;
+	}
 }
diff --git a/tut9/src/FunctionalSetIterator.java b/tut9/src/FunctionalSetIterator.java
new file mode 100644
index 0000000..ef411e6
--- /dev/null
+++ b/tut9/src/FunctionalSetIterator.java
@@ -0,0 +1,67 @@
+import java.util.*;
+
+public class FunctionalSetIterator<E> implements Iterator<E>
+{
+	/** Unsere Menge */
+	private FunctionalSet<E> set;
+	/** Aktuelles Element */
+	private SimpleFunctionalSet<E> current;
+	/** Bereits gesehene Elemente */
+	private Set<Object> seen = new FunctionalSet<>();
+	/** Aktuelles Element */
+	private E currentElem;
+	/** Ob das aktuelle Element bereits entfernt wurde. */
+	private boolean hasBeenRemoved = true;
+	
+	private void skipToNext()
+	{
+		while (true)
+		{
+			current = current.getRemainingSet();
+			if (current instanceof RemoveSet)
+				seen.add(((RemoveSet) current).getObject());
+			else if (!(current instanceof AddSet) || !seen.contains(((AddSet)current).getElement()))
+				break;
+		}
+	}
+	
+	public FunctionalSetIterator(FunctionalSet<E> set, SimpleFunctionalSet<E> head)
+	{
+		this.set = set;
+		current = head;
+		if (current instanceof RemoveSet)
+		{
+			seen.add(((RemoveSet)current).getObject());
+			skipToNext();
+		}
+	}
+	
+	@Override
+	public boolean hasNext()
+	{
+		return !(current instanceof EmptySet);
+	}
+	
+	@Override
+	public E next()
+	{
+		if (!hasNext())
+			throw new NoSuchElementException();
+		
+		currentElem = ((AddSet<E>) current).getElement();
+		seen.add(currentElem);
+		skipToNext();
+		hasBeenRemoved = false;
+		return currentElem;
+	}
+	
+	@Override
+	public void remove()
+	{
+		if (hasBeenRemoved)
+			throw new IllegalStateException("Das Element wurde schon entfernt");
+		
+		set.remove(currentElem);
+		hasBeenRemoved = true;
+	}
+}
diff --git a/tut9/src/Main.java b/tut9/src/Main.java
index f20acd6..c994516 100644
--- a/tut9/src/Main.java
+++ b/tut9/src/Main.java
@@ -15,15 +15,36 @@ public class Main
 				case "exit":
 					break;
 				case "add":
-					s.add(Integer.parseInt(words[1]));
-					System.out.println(s);
+					try
+					{
+						s.add(Integer.parseInt(words[1]));
+						System.out.println(s);
+					}
+					catch (NumberFormatException nfe)
+					{
+						System.out.println("FEHLER: Eingabe ungültig!");
+					}
 					break;
 				case "remove":
-					s.remove(Integer.parseInt(words[1]));
-					System.out.println(s);
+					try
+					{
+						s.remove(Integer.parseInt(words[1]));
+						System.out.println(s);
+					}
+					catch (NumberFormatException nfe)
+					{
+						System.out.println("FEHLER: Eingabe ungültig!");
+					}
 					break;
 				case "min":
-					System.out.println(s.min(Comparator.<Integer>naturalOrder()));
+					try
+					{
+						System.out.println(s.min(Comparator.naturalOrder()));
+					}
+					catch (MinimumOfEmptySetException moese)
+					{
+						System.out.println("FEHLER: Set enthaelt keine Elemente");
+					}
 					break;
 				default:
 					System.out.println("Unknown command.");
diff --git a/tut9/src/MinimumOfEmptySetException.java b/tut9/src/MinimumOfEmptySetException.java
new file mode 100644
index 0000000..3e52b8b
--- /dev/null
+++ b/tut9/src/MinimumOfEmptySetException.java
@@ -0,0 +1,4 @@
+public class MinimumOfEmptySetException extends RuntimeException
+{
+
+}