Augment documentation.

git-svn-id: https://svn.dealii.org/trunk@27877 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/examples/step-6/step-6.cc b/deal.II/examples/step-6/step-6.cc
index 068fe9a410effadb4a509dfca3e4b7b34b6ba630..7a5ab147781defae5973482363fff8554c4a2312 100644 (file)
--- a/deal.II/examples/step-6/step-6.cc
+++ b/deal.II/examples/step-6/step-6.cc
@@ -329,16 +329,19 @@ void Step6<dim>::setup_system ()
   // previous examples. Nevertheless, we do not copy it to the final sparsity
   // pattern immediately.  Note that we call a variant of
   // make_sparsity_pattern that takes the ConstraintMatrix as the third
-  // argument. We are letting the routine know, the we will never write into
+  // argument. We are letting the routine know that we will never write into
   // the locations given by <code>constraints</code> by setting the argument
-  // <code>keep_constrained_dofs</code> to false. If we were to condense the
+  // <code>keep_constrained_dofs</code> to false (in other words, that we will
+  // never write into entries of the matrix that correspond to constrained
+  // degrees of freedom). If we were to condense the
   // constraints after assembling, we would have to pass <code>true</code>
-  // instead.
+  // instead because then we would first write into these locations only to
+  // later set them to zero again during condensation.
   CompressedSparsityPattern c_sparsity(dof_handler.n_dofs());
   DoFTools::make_sparsity_pattern(dof_handler,
                                   c_sparsity,
                                   constraints,
-                                  false /*keep_constrained_dofs*/);
+                                  /*keep_constrained_dofs = */ false);
 
   // Now all non-zero entries of the matrix are known (i.e. those from
   // regularly assembling the matrix and those that were introduced by