From: Wolfgang Bangerth <bangerth@math.tamu.edu>
Date: Mon, 6 Apr 2015 15:38:44 +0000 (-0500)
Subject: Update docs for a statement one of my students just stumbled over.
X-Git-Tag: v8.3.0-rc1~313^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F739%2Fhead;p=dealii.git

Update docs for a statement one of my students just stumbled over.
---

diff --git a/examples/step-49/step-49.cc b/examples/step-49/step-49.cc
index 592cafc54c..456205758f 100644
--- a/examples/step-49/step-49.cc
+++ b/examples/step-49/step-49.cc
@@ -65,8 +65,11 @@ void mesh_info(const Triangulation<dim> &tria,
             << " dimension: " << dim << std::endl
             << " no. of cells: " << tria.n_active_cells() << std::endl;
 
-  // Next loop over all faces of all cells and find how often each boundary
-  // indicator is used:
+  // Next loop over all faces of all cells and find how often each
+  // boundary indicator is used (recall that if you access an element
+  // of a std::map object that doesn't exist, it is implicitly created
+  // and default initialized -- to zero, in the current case -- before
+  // we then increment it):
   {
     std::map<unsigned int, unsigned int> boundary_count;
     typename Triangulation<dim>::active_cell_iterator