[test]Replace ConstantFunction by Dune::makeVirtualFunction

This still uses the deprecated function interface, but at least allows to get
rid of the function implementation. Adjusting the assemblers is a separate task.

dune/fufem/test/generalizedlaplaceassemblertest.cc

@@ -8,9 +8,9 @@
 #include <dune/common/exceptions.hh>
 #include <dune/common/fvector.hh>
 #include <dune/common/fmatrix.hh>
+#include <dune/common/function.hh>
 #include <dune/istl/bvector.hh>
 
-#include <dune/fufem/functions/constantfunction.hh>
 #include <dune/fufem/functions/virtualgridfunction.hh>
 #include <dune/fufem/functions/virtualdifferentiablefunction.hh>
 
@@ -109,17 +109,17 @@ struct GeneralizedLaplaceAssemblerTestSuite
         typedef typename GridType::template Codim<0>::Geometry::GlobalCoordinate DomainType;
         typedef Dune::FieldMatrix<double, dim, dim> MatrixRangeType;
 
-        typedef ConstantFunction<DomainType, ScalarRangeType> ConstantScalarFunction;
-        ConstantScalarFunction scalarconstant1(1.0);
-        ConstantScalarFunction scalarconstant2(2.0);
+        using ConstantScalarFunction = Dune::VirtualFunction<DomainType, ScalarRangeType>;
+        auto scalarconstant1 = Dune::makeVirtualFunction<DomainType, ScalarRangeType>([](auto&&){ return 1.0;});
+        auto scalarconstant2 = Dune::makeVirtualFunction<DomainType, ScalarRangeType>([](auto&&){ return 2.0;});
 
         MatrixRangeType diag(0.0);
         for (int d=0; d<dim; ++d)
             diag[d][d] = 1.0;
-        typedef ConstantFunction<DomainType, MatrixRangeType> ConstantMatrixFunction;
-        ConstantMatrixFunction matrixconstant1(diag);
+        using ConstantMatrixFunction = Dune::VirtualFunction<DomainType, MatrixRangeType>;
+        auto matrixconstant1 = Dune::makeVirtualFunction<DomainType, MatrixRangeType>([=](auto&&){ return diag;});
         diag *= 2.0;
-        ConstantMatrixFunction matrixconstant2(diag);
+        auto matrixconstant2 = Dune::makeVirtualFunction<DomainType, MatrixRangeType>([=](auto&&){ return diag;});
 
         Assembler<FufemBasis, FufemBasis> assembler(fufemBasis, fufemBasis);