Use a reference to a const value in one place

diff --git a/include/deal.II/base/index_set.h b/include/deal.II/base/index_set.h
index c9abbddc7a6f489622596b988cf93c7ef1f21dd9..7e803b8ec31e9692d130b8d8a005d504662a3574 100644 (file)
--- a/include/deal.II/base/index_set.h
+++ b/include/deal.II/base/index_set.h
@@ -1831,8 +1831,8 @@ IndexSet::n_elements() const
   size_type v = 0;
   if (!ranges.empty())
     {
-      Range &r = ranges.back();
-      v        = r.nth_index_in_set + r.end - r.begin;
+      const Range &r = ranges.back();
+      v              = r.nth_index_in_set + r.end - r.begin;
     }
 
 #ifdef DEBUG