Allow StrainProductAssembler to have variable coefficients

[[Imported from SVN: r12872]]

dune/fufem/assemblers/localassemblers/strainproductassembler.hh

@@ -18,6 +18,14 @@ class StrainProductAssembler
         static const int dim = GridType::dimension;
         typedef typename GridType::ctype ctype;
 
+        StrainProductAssembler()
+          : coefficientQuadKey_(dim, 0)
+        {}
+
+        StrainProductAssembler(QuadratureRuleKey const &coefficientQuadKey)
+          : coefficientQuadKey_(coefficientQuadKey)
+        {}
+
     public:
         typedef typename Dune::FieldMatrix<ctype,GridType::dimension,GridType::dimension> T;
 
@@ -43,7 +51,8 @@ class StrainProductAssembler
         localMatrix.setSize(rows,cols);
         localMatrix = 0.0;
 
-        QuadratureRuleKey quadKey = QuadratureRuleKey(tFE).derivative()
+        QuadratureRuleKey quadKey = coefficientQuadKey_
+          .product(QuadratureRuleKey(tFE).derivative())
           .product(QuadratureRuleKey(aFE).derivative());
         const Dune::template QuadratureRule<ctype, dim>& quad
             = QuadratureRuleCache<ctype, dim>::rule(quadKey);
@@ -142,6 +151,9 @@ class StrainProductAssembler
                                       const Dune::FieldVector<ctype, dim>& position) const {
     return static_cast<const A*>(this)->strainToStress(strain, element, position);
   }
+
+private:
+    const QuadratureRuleKey coefficientQuadKey_;
 };