From 4bdd5aec2d3ba23fc49d39dd559d9197ab81fc20 Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Thu, 23 Aug 2018 15:06:09 -0600
Subject: [PATCH] Avoid loop increment operations with side effects.

Just because it can be done does not mean that it *should* be done.
---
 examples/step-10/step-10.cc | 19 ++++++++-----------
 examples/step-11/step-11.cc |  7 ++++---
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/examples/step-10/step-10.cc b/examples/step-10/step-10.cc
index 8ddacbf912..8b6215f52b 100644
--- a/examples/step-10/step-10.cc
+++ b/examples/step-10/step-10.cc
@@ -83,21 +83,15 @@ namespace Step10
     Triangulation<dim> triangulation;
     GridGenerator::hyper_ball(triangulation);
 
-    // Next generate output for this grid and for a once refined grid. Note
-    // that we have hidden the mesh refinement in the loop header, which might
-    // be uncommon but nevertheless works. Also it is strangely consistent
-    // with incrementing the loop index denoting the refinement level.
-    for (unsigned int refinement = 0; refinement < 2;
-         ++refinement, triangulation.refine_global(1))
+    // Then alternate between generating output on the current mesh
+    // for $Q_1$, $Q_2$, and $Q_3$ mappings, and (at the end of the
+    // loop body) refining the mesh once globally.
+    for (unsigned int refinement = 0; refinement < 2; ++refinement)
       {
         std::cout << "Refinement level: " << refinement << std::endl;
 
-        // Then have a string which denotes the base part of the names of the
-        // files into which we write the output (ending with the refinement
-        // level).
         std::string filename_base = "ball_" + Utilities::to_string(refinement);
 
-        // Then output the present grid for $Q_1$, $Q_2$, and $Q_3$ mappings:
         for (unsigned int degree = 1; degree < 4; ++degree)
           {
             std::cout << "Degree = " << degree << std::endl;
@@ -118,7 +112,7 @@ namespace Step10
             // explicitly.
 
 
-            // In degree to actually write out the present grid with this
+            // In order to actually write out the present grid with this
             // mapping, we set up an object which we will use for output. We
             // will generate Gnuplot output, which consists of a set of lines
             // describing the mapped triangulation. By default, only one line
@@ -149,6 +143,9 @@ namespace Step10
             grid_out.write_gnuplot(triangulation, gnuplot_file, &mapping);
           }
         std::cout << std::endl;
+
+        // At the end of the loop, refine the mesh globally.
+        triangulation.refine_global();
       }
   }
 
diff --git a/examples/step-11/step-11.cc b/examples/step-11/step-11.cc
index 61550df2d4..775f54fd5f 100644
--- a/examples/step-11/step-11.cc
+++ b/examples/step-11/step-11.cc
@@ -415,12 +415,13 @@ namespace Step11
   {
     GridGenerator::hyper_ball(triangulation);
 
-    for (unsigned int cycle = 0; cycle < 6;
-         ++cycle, triangulation.refine_global(1))
+    for (unsigned int cycle = 0; cycle < 6; ++cycle)
       {
         setup_system();
         assemble_and_solve();
-      };
+
+        triangulation.refine_global();
+      }
 
     // After all the data is generated, write a table of results to the
     // screen:
-- 
2.39.5