Update README.md

README.md

@@ -34,25 +34,26 @@ DecGrid<GridBase> grid(*gridBase);
 
 This grid adapter provides iterators for incidence relations, like edges of a vertex or faces of an edge.
 
-Example: Iterate over all edges of the grid and store the coefficients of a Grad-Div laplacian
+Example: Iterate over all edges of the grid (grid-view) and store the coefficients of a Grad-Div laplacian
 in a sparse matrix:
 ```c++
-DOFMatrix<double> A(grid.size(1), grid.size(1)); // sparse matrix with num_rows=#edges
+auto gv = grid.leafGridView();
+DOFMatrix<double> A(gv.size(1), gv.size(1)); // sparse matrix with num_rows=#edges
 
-auto const& I = grid.indexSet();
+auto const& I = gv.indexSet();
 
 { auto ins = A.inserter();
 
 // iterator over all edges in the grid
-for (auto const& e : edges(grid.gridView())) {
+for (auto const& e : edges(gv)) {
 
   // iterate over all vertices incident to edge e
   for (auto const& v : vertices(e)) {
-    auto factor1 = v.sign(e) * grid.dual_volume(v);
+    auto factor1 = v.sign(e) * gv.dual_volume(v);
     
     // iterate over all edges incident to vertex v
     for (auto const& e_ : edges(v)) {
-      auto factor2 = v.sign(e_) * grid.dual_volume(e_) / grid.volume(e_);
+      auto factor2 = v.sign(e_) * gv.dual_volume(e_) / gv.volume(e_);
       
       ins(I.index(e), I.index(e_)) << factor1 * factor2;
     }