diff --git a/ikarus/CMakeLists.txt b/ikarus/CMakeLists.txt
index 7aba01630..7cfdce156 100644
--- a/ikarus/CMakeLists.txt
+++ b/ikarus/CMakeLists.txt
@@ -9,7 +9,6 @@ file(
   CONFIGURE_DEPENDS *.cpp
 )
 
-
 dune_enable_all_packages()
 dune_add_library(
   ${PROJECT_NAME}
diff --git a/ikarus/io/resultevaluators.hh b/ikarus/io/resultevaluators.hh
index f47824285..5e2951b63 100644
--- a/ikarus/io/resultevaluators.hh
+++ b/ikarus/io/resultevaluators.hh
@@ -112,7 +112,7 @@ struct PrincipalStress
                     const int comp) const {
     auto mat = fromVoigt(resultArray, false);
     Eigen::SelfAdjointEigenSolver<decltype(mat)> eigensolver(mat, Eigen::EigenvaluesOnly);
-    return eigensolver.eigenvalues()[dim - 1 - comp];
+    return eigensolver.eigenvalues().reverse()[comp];
   }
 
   /**
@@ -164,9 +164,9 @@ struct Triaxiality
 };
 
 /**
- * \brief Struct for calculating the 2d polar stress. The center of the coordinate system is chosen to be the center of
- * the corresponding reference geometry.
-  \ingroup resultevaluators
+ * \brief Struct for calculating the 2d polar stress. The center of the coordinate system is to be passed to the
+ * evaluator.
+ * \ingroup resultevaluators
  */
 struct PolarStress
 {
@@ -200,8 +200,10 @@ struct PolarStress
         return polarStress(0, 0);
       case 1:
         return polarStress(1, 1);
-      default: // 2
+      case 2:
         return polarStress(1, 0);
+      default:
+        __builtin_unreachable();
     }
   }
 
diff --git a/ikarus/io/resultfunction.hh b/ikarus/io/resultfunction.hh
index b918928e6..af60889ea 100644
--- a/ikarus/io/resultfunction.hh
+++ b/ikarus/io/resultfunction.hh
@@ -29,8 +29,11 @@ namespace Impl {
      * \tparam R Type of the matrix
      * \return the result
      */
-    template <typename R>
-    double operator()(const R& resultArray, const auto& pos, const auto& fe, const int comp) const {};
+    template <typename R, typename FiniteElement, int dim>
+    double operator()(const R& resultArray, const Dune::FieldVector<double, dim>& pos, const FiniteElement& fe,
+                      const int comp) const {
+      return resultArray[comp];
+    };
   };
 } // namespace Impl
 
@@ -101,7 +104,7 @@ public:
   }
 
   /**
-   * \brief Get the name of the result type.P
+   * \brief Get the name of the result type.
    * \details
    * This function is required by the Dune::VTKFunction interface.
    *
@@ -127,14 +130,14 @@ public:
   /**
    * \brief Construct a new Result Function object
    *
-   * \tparam Args Type of additional arguments passed to the user function
+   * \tparam UF Type of the user function
    * \param assembler shared pointer to the underlying assembler (provides the finite elements and the requested
    * results)
    * \param prec (optional) specify the used precision (only has an effect when using resultfunciton with
    * Dune::VTK::VTKWriter)
    * \param userFunction the user function (default is DefaultUserFunction)
    */
-  template <typename UF>
+  template <typename UF = UserFunction>
   ResultFunction(std::shared_ptr<Assembler> assembler, Dune::VTK::Precision prec = Dune::VTK::Precision::float64,
                  UF&& userFunction = {})
       : assembler_(assembler),
@@ -146,10 +149,7 @@ private:
     const auto& fe = finiteElements().at(eleID);
     auto result    = fe.template calculateAt<RT>(requirement(), local).asVec();
 
-    if constexpr (!std::is_same_v<UserFunction, Impl::DefaultUserFunction>) {
-      return userFunction_(result, local, fe, comp);
-    } else
-      return result(comp);
+    return userFunction_(result, local, fe, comp);
   }
 
   const FEContainer& finiteElements() const { return assembler_->finiteElements(); }
@@ -166,15 +166,17 @@ private:
  * \brief Function to create a ResultFunction as a shared_ptr
  * \details
  * Constructs a ResultFunction object with given assembler as shared_ptr to be used with the native Dune VTKWriter
- *
  * \param assembler shared pointer to the underlying assembler (provides the finite elements and the requested
- * results) \tparam AS type of the assembler \tparam RT requested result type \tparam UserFunction Type of the
- * user-defined function for custom result evaluation (default is DefaultUserFunction) \param assembler shared pointer
- * to the underlying assembler (provides the finite elements and the requested results) \param prec (optional) specify
- * the used precision \param userFunction (optional) the user function (default is DefaultUserFunction)
+ * results)
+ * \tparam AS type of the assembler
+ * \tparam RT requested result type
+ * \tparam UserFunction Type of the user-defined function for custom result evaluation (default is DefaultUserFunction)
+ * \param assembler shared pointer to the underlying assembler (provides the finite elements and the requested results)
+ * \param prec (optional) specify the used precision
+ * \param userFunction (optional) the user function (default is DefaultUserFunction)
  */
 template <template <typename, int, int> class RT, typename UserFunction = Impl::DefaultUserFunction,
-          Concepts::FlatAssembler AS, typename... Args>
+          Concepts::FlatAssembler AS>
 auto makeResultFunction(std::shared_ptr<AS> assembler, Dune::VTK::Precision prec = Dune::VTK::Precision::float64,
                         UserFunction&& userFunction = {}) {
   return std::make_shared<ResultFunction<AS, RT, UserFunction>>(assembler, prec,
@@ -185,14 +187,13 @@ auto makeResultFunction(std::shared_ptr<AS> assembler, Dune::VTK::Precision prec
  * \brief Function to create a ResultFunction as a shared_ptr
  * \details
  * Constructs a ResultFunction object with given assembler as shared_ptr to be used with the native Dune VTKWriter
- *
- * \param assembler shared pointer to the underlying assembler (provides the finite elements and the requested
- * results) \tparam AS type of the assembler \tparam RT requested result type \tparam UserFunction Type of the
- * user-defined function for custom result evaluation \param assembler shared pointer to the underlying assembler
- * (provides the finite elements and the requested results) \param userFunction  the user function
+ * \tparam AS type of the assembler
+ * \tparam RT requested result type
+ * \tparam UserFunction Type of the user-defined function for custom result evaluation (default is DefaultUserFunction)
+ * \param assembler shared pointer to the underlying assembler (provides the finite elements and the requested results)
+ * \param userFunction  the user function
  */
-template <template <typename, int, int> class RT, typename UserFunction = Impl::DefaultUserFunction,
-          Concepts::FlatAssembler AS, typename... Args>
+template <template <typename, int, int> class RT, typename UserFunction, Concepts::FlatAssembler AS>
 auto makeResultFunction(std::shared_ptr<AS> assembler, UserFunction&& userFunction) {
   return makeResultFunction<RT>(assembler, Dune::VTK::Precision::float64, std::forward<UserFunction>(userFunction));
 }
@@ -200,17 +201,21 @@ auto makeResultFunction(std::shared_ptr<AS> assembler, UserFunction&& userFuncti
 /**
  * \brief Function to create a ResultFunction as a gridfunction that can be used with dune-vtk
  * \details
- * Constructs a ResultFunction object with given assembler as a VTK::Function to be used withdune-vtk It is possible
- * to construct a localFunction from this as follows \code auto localResultFunction =
- * localFunction(vtkResultFunction); localResultFunction.bind(element); \endcode \tparam AS type of the assembler
+ * Constructs a ResultFunction object with given finite elements, ferequirements as a VTK::Function to be used with
+ * dune-vtk It is possible to construct a localFunction from this as follows
+ * \code
+ * auto localResultFunction = localFunction(vtkResultFunction);
+ * localResultFunction.bind(element);
+ * \endcode
+ * \tparam AS  type of the assembler
  * \tparam RT requested result type
  * \tparam UserFunction Type of the user-defined function for custom result evaluation (default is
  * DefaultUserFunction)
- * \param assembler shared pointer to the underlying assembler (provides the finite elements and the requested
- * results) \param userFunction the user function (default is DefaultUserFunction)
+ * \param userFunction (optional) the user function (default is DefaultUserFunction)
+ * \param assembler shared pointer to the underlying assembler (provides the finite elements and the requested results)
  */
 template <template <typename, int, int> class RT, typename UserFunction = Impl::DefaultUserFunction,
-          Concepts::FlatAssembler AS, typename... Args>
+          Concepts::FlatAssembler AS>
 auto makeResultVtkFunction(std::shared_ptr<AS> assembler, UserFunction&& userFunction = {}) {
   return Dune::Vtk::Function<typename AS::GridView>(std::make_shared<ResultFunction<AS, RT, UserFunction>>(
       assembler, Dune::VTK::Precision::float64, std::forward<UserFunction>(userFunction)));