A bit further.

git-svn-id: https://svn.dealii.org/trunk@16074 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/examples/step-33/step-33.cc b/deal.II/examples/step-33/step-33.cc
index 33b1ed1333b5514671f89e754fafb73d716ce4f6..d30e11a3e37421e6973cc10b65277b3d5d6b308d 100644 (file)
--- a/deal.II/examples/step-33/step-33.cc
+++ b/deal.II/examples/step-33/step-33.cc
@@ -93,7 +93,6 @@
                                 // namespace:
 using namespace dealii;
 
-#define DIMENSION 2
 
                                 // @sect3{Flux function definition}
 
@@ -115,10 +114,25 @@ using namespace dealii;
                                 // introduce using a template parameter:
 namespace EulerEquations
 {
-                                  // We define the number of components in
-                                  // the system.  Euler's has one entry for
-                                  // momenta in each spatial direction, plus
-                                  // the energy and density components.
+                                  // First a few inline functions that
+                                  // describe the various components of our
+                                  // solution vector in a generic way. This
+                                  // includes the number of components in the
+                                  // system (Euler's equations have one entry
+                                  // for momenta in each spatial direction,
+                                  // plus the energy and density components,
+                                  // for a total of <code>dim+2</code>
+                                  // components), as well as functions that
+                                  // describe the index within the solution
+                                  // vector of the first momentum component,
+                                  // the density component, and the energy
+                                  // density component. Note that all these
+                                  // numbers depend on the space dimension;
+                                  // defining them in a generic way (rather
+                                  // than by implicit convention) makes our
+                                  // code more flexible and makes it easier
+                                  // to later extend it, for example by
+                                  // adding more components to the equations.
   template <int dim>
   inline
   unsigned int n_components ()
@@ -126,11 +140,13 @@ namespace EulerEquations
     return dim + 2;
   }
 
+  template <int dim>
+  inline
+  unsigned int first_momentum_component ()
+  {
+    return 0;
+  }
 
-                                // Define a handle to the density and energy
-                                // indices.  We have arrange the momenta to
-                                // be first, then density, and, lastly,
-                                // energy.
   template <int dim>
   inline
   unsigned int density_component ()
@@ -138,8 +154,6 @@ namespace EulerEquations
     return dim;
   }
 
-
-
   template <int dim>
   inline
   unsigned int energy_component ()
@@ -148,8 +162,12 @@ namespace EulerEquations
   }
   
 
-                                  // The gas constant.  This value is
-                                  // representative of air.
+                                  // Next, we define the gas constant.  This
+                                  // value is representative of a gas that
+                                  // consists of molecules composed of two
+                                  // atoms, such as air which consists up to
+                                  // small traces almost entirely of $N_2$
+                                  // and $O_2$.
   const double gas_gamma = 1.4;
 }
 
@@ -169,7 +187,7 @@ using namespace EulerEquations;
                                 // exactly like the Euler equations one is
                                 // used to seeing.  We evaluate the flux at a
                                 // single quadrature point.
-template <typename number, int dim>
+template <int dim, typename number>
 void Flux(std::vector<std::vector<number> >  &flux, 
           const Point<dim> &/*point*/,
           const std::vector<number> &W)
@@ -2113,7 +2131,7 @@ int main (int argc, char *argv[])
   }
   try
     {
-      ConsLaw<DIMENSION> cons;
+      ConsLaw<2> cons;
       cons.declare_parameters();
       cons.load_parameters(argv[1]);
       cons.run ();