NeumannEnergy: use std::function instead of Dune::VirtualFunction

We also use std::shared_ptr's instead of C-pointers.

dune/elasticity/materials/neumannenergy.hh

 #ifndef DUNE_ELASTICITY_MATERIALS_NEUMANNENERGY_HH
 #define DUNE_ELASTICITY_MATERIALS_NEUMANNENERGY_HH
 
+#include <functional>
+
 #include <dune/geometry/quadraturerules.hh>
 
-#include <dune/fufem/functions/virtualgridfunction.hh>
 #include <dune/fufem/boundarypatch.hh>
 
 #include <dune/elasticity/assemblers/localenergy.hh>
@@ -26,7 +27,7 @@ public:
    * \param parameters The material parameters
    */
   NeumannEnergy(const std::shared_ptr<BoundaryPatch<GridView>>& neumannBoundary,
-                const Dune::VirtualFunction<Dune::FieldVector<ctype,dim>, Dune::FieldVector<double,dim> >* neumannFunction)
+                const std::shared_ptr<std::function<Dune::FieldVector<double,dim>(Dune::FieldVector<ctype,dim>)>>& neumannFunction)
   : neumannBoundary_(neumannBoundary),
     neumannFunction_(neumannFunction)
   {}
@@ -66,12 +67,7 @@ public:
             value[j] += shapeFunctionValues[i] * localConfiguration[ localView.tree().child(j).localIndex(i) ];
 
         // Value of the Neumann data at the current position
-        Dune::FieldVector<double,dim> neumannValue;
-
-        if (dynamic_cast<const VirtualGridViewFunction<GridView,Dune::FieldVector<double,dim> >*>(neumannFunction_))
-            dynamic_cast<const VirtualGridViewFunction<GridView,Dune::FieldVector<double,dim> >*>(neumannFunction_)->evaluateLocal(element, quadPos, neumannValue);
-        else
-            neumannFunction_->evaluate(it.geometry().global(quad[pt].position()), neumannValue);
+        auto neumannValue = (*neumannFunction_)( it.geometry().global(quad[pt].position()) );
 
         // Only translational dofs are affected by the Neumann force
         for (size_t i=0; i<neumannValue.size(); i++)
@@ -89,7 +85,7 @@ private:
   const std::shared_ptr<BoundaryPatch<GridView>> neumannBoundary_;
 
   /** \brief The function implementing the Neumann data */
-  const Dune::VirtualFunction<Dune::FieldVector<double,dim>, Dune::FieldVector<double,dim> >* neumannFunction_;
+  const std::shared_ptr<std::function<Dune::FieldVector<double,dim>(Dune::FieldVector<ctype,dim>)>> neumannFunction_;
 };
 
 }  // namespace Dune::Elasticity
@@ -113,8 +109,8 @@ public:
   /** \brief Constructor with a set of material parameters
    * \param parameters The material parameters
    */
-  NeumannEnergy(const BoundaryPatch<GridView>* neumannBoundary,
-                const Dune::VirtualFunction<Dune::FieldVector<ctype,dim>, Dune::FieldVector<double,dim> >* neumannFunction)
+  NeumannEnergy(const std::shared_ptr<BoundaryPatch<GridView>>& neumannBoundary,
+                const std::shared_ptr<std::function<Dune::FieldVector<double,dim>(Dune::FieldVector<ctype,dim>)>>& neumannFunction)
   : neumannBoundary_(neumannBoundary),
     neumannFunction_(neumannFunction)
   {}
@@ -154,12 +150,8 @@ public:
             value[j] += shapeFunctionValues[i] * localConfiguration[i][j];
 
         // Value of the Neumann data at the current position
-        Dune::FieldVector<double,dim> neumannValue;
+        auto neumannValue = (*neumannFunction_)( it.geometry().global(quad[pt].position()) );
 
-        if (dynamic_cast<const VirtualGridViewFunction<GridView,Dune::FieldVector<double,dim> >*>(neumannFunction_))
-            dynamic_cast<const VirtualGridViewFunction<GridView,Dune::FieldVector<double,dim> >*>(neumannFunction_)->evaluateLocal(element, quadPos, neumannValue);
-        else
-            neumannFunction_->evaluate(it.geometry().global(quad[pt].position()), neumannValue);
 
         // Only translational dofs are affected by the Neumann force
         for (size_t i=0; i<neumannValue.size(); i++)
@@ -174,10 +166,10 @@ public:
 
 private:
   /** \brief The Neumann boundary */
-  const BoundaryPatch<GridView>* neumannBoundary_;
+  const std::shared_ptr<BoundaryPatch<GridView>> neumannBoundary_;
 
   /** \brief The function implementing the Neumann data */
-  const Dune::VirtualFunction<Dune::FieldVector<double,dim>, Dune::FieldVector<double,dim> >* neumannFunction_;
+  const std::shared_ptr<std::function<Dune::FieldVector<double,dim>(Dune::FieldVector<ctype,dim>)>> neumannFunction_;
 };
 
 }  // namespace Dune