Index: branches/2925_AutoDiffForDynamicalModels/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Interpreter/IntervalInterpreter.cs
===================================================================
--- branches/2925_AutoDiffForDynamicalModels/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Interpreter/IntervalInterpreter.cs	(revision 16662)
+++ branches/2925_AutoDiffForDynamicalModels/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Interpreter/IntervalInterpreter.cs	(revision 16892)
@@ -69,16 +69,16 @@
     #endregion
 
-    public Interval GetSymbolicExressionTreeInterval(ISymbolicExpressionTree tree, IDataset dataset, IEnumerable<int> rows = null) {
+    public Interval GetSymbolicExpressionTreeInterval(ISymbolicExpressionTree tree, IDataset dataset, IEnumerable<int> rows = null) {
       var variableRanges = DatasetUtil.GetVariableRanges(dataset, rows);
-      return GetSymbolicExressionTreeInterval(tree, variableRanges);
-    }
-
-    public Interval GetSymbolicExressionTreeIntervals(ISymbolicExpressionTree tree, IDataset dataset,
-      out Dictionary<ISymbolicExpressionTreeNode, Interval> nodeIntervals, IEnumerable<int> rows = null) {
+      return GetSymbolicExpressionTreeInterval(tree, variableRanges);
+    }
+
+    public Interval GetSymbolicExpressionTreeIntervals(ISymbolicExpressionTree tree, IDataset dataset,
+      out IDictionary<ISymbolicExpressionTreeNode, Interval> nodeIntervals, IEnumerable<int> rows = null) {
       var variableRanges = DatasetUtil.GetVariableRanges(dataset, rows);
-      return GetSymbolicExressionTreeIntervals(tree, variableRanges, out nodeIntervals);
-    }
-
-    public Interval GetSymbolicExressionTreeInterval(ISymbolicExpressionTree tree, Dictionary<string, Interval> variableRanges) {
+      return GetSymbolicExpressionTreeIntervals(tree, variableRanges, out nodeIntervals);
+    }
+
+    public Interval GetSymbolicExpressionTreeInterval(ISymbolicExpressionTree tree, IDictionary<string, Interval> variableRanges) {
       lock (syncRoot) {
         EvaluatedSolutions++;
@@ -96,6 +96,6 @@
 
 
-    public Interval GetSymbolicExressionTreeIntervals(ISymbolicExpressionTree tree,
-      Dictionary<string, Interval> variableRanges, out Dictionary<ISymbolicExpressionTreeNode, Interval> nodeIntervals) {
+    public Interval GetSymbolicExpressionTreeIntervals(ISymbolicExpressionTree tree,
+      IDictionary<string, Interval> variableRanges, out IDictionary<ISymbolicExpressionTreeNode, Interval> nodeIntervals) {
       lock (syncRoot) {
         EvaluatedSolutions++;
@@ -108,5 +108,5 @@
       // fix incorrect intervals if necessary (could occur because of numerical errors)
       nodeIntervals = new Dictionary<ISymbolicExpressionTreeNode, Interval>();
-      foreach(var kvp in intervals) {
+      foreach (var kvp in intervals) {
         var interval = kvp.Value;
         if (interval.IsInfiniteOrUndefined || interval.LowerBound <= interval.UpperBound)
@@ -124,5 +124,5 @@
 
 
-    private static Instruction[] PrepareInterpreterState(ISymbolicExpressionTree tree, Dictionary<string, Interval> variableRanges) {
+    private static Instruction[] PrepareInterpreterState(ISymbolicExpressionTree tree, IDictionary<string, Interval> variableRanges) {
       if (variableRanges == null)
         throw new ArgumentNullException("No variablew ranges are present!", nameof(variableRanges));
@@ -141,5 +141,5 @@
     }
 
-    private Interval Evaluate(Instruction[] instructions, ref int instructionCounter, Dictionary<ISymbolicExpressionTreeNode, Interval> nodeIntervals = null) {
+    private Interval Evaluate(Instruction[] instructions, ref int instructionCounter, IDictionary<ISymbolicExpressionTreeNode, Interval> nodeIntervals = null) {
       Instruction currentInstr = instructions[instructionCounter];
       //Use ref parameter, because the tree will be iterated through recursively from the left-side branch to the right side
@@ -216,4 +216,9 @@
             var argumentInterval = Evaluate(instructions, ref instructionCounter, nodeIntervals);
             result = Interval.Tangens(argumentInterval);
+            break;
+          }
+        case OpCodes.Tanh: {
+            var argumentInterval = Evaluate(instructions, ref instructionCounter, nodeIntervals);
+            result = Interval.HyperbolicTangent(argumentInterval);
             break;
           }
