add test case for python fix

dune/fufem/test/dunepythontest.cc

@@ -800,6 +800,35 @@ int main(int argc, char** argv)
     }
 #endif
 
+    std::cout << std::endl;
+    std::cout << "Example 18: calling functions with Fieldvector multiple times ******************" << std::endl;
+    {
+        using Vec3D = Dune::FieldVector<double, 3>;
+        using Vec2D = Dune::FieldVector<double, 2>;
+	using Vec1D = Dune::FieldVector<double, 1>;
+
+	Vec3D a{0.5,0.5,0.5};
+	Vec2D b{0.5,0.5};
+	Vec1D c{0.5};
+
+	auto test3d = Python::make_function<Vec3D>(Python::evaluate("lambda x: (0.0, 0.0, 0.0)"));
+	auto test2d = Python::make_function<Vec2D>(Python::evaluate("lambda x: (0.0, 0.0)"));
+	auto test1d = Python::make_function<Vec1D>(Python::evaluate("lambda x: (0.0)"));
+
+        int nloop=2;
+	std::cout << "multiple calls with 3d Fieldvector... "<< std::endl;
+	for (int i=0; i<nloop; ++i)
+	  std::cout << i << ". call "<< test3d(a) << " should be (0,0,0)" << std::endl;
+
+	std::cout << "multiple calls with 2d Fieldvector... "<< std::endl;
+	for (int i=0; i<nloop; ++i)
+	  std::cout << i << ". call "<< test2d(b) << " should be (0,0)" << std::endl;
+
+	std::cout << "multiple calls with 1d Fieldvector... "<< std::endl;
+	for (int i=0; i<nloop; ++i)
+	  std::cout << i << ". call "<< test1d(c) << " should be (0)" << std::endl;
+    }
+
     // Before exiting you should stop the python interpreter.
     Python::stop();