put before the data type specifier, i.e., we use Point<dim,number> and not
Point<number,dim>.
+<li> There are several places in deal.II where we use forward declarations in
+ header files. The reason for this is that we can, hopefully, improve
+ compilation speeds by not using headers when we just need to mark a certain
+ type as an argument to a function. The convention used in deal.II is that, if
+ all we need is a type name, then the type may be forward declared in the
+ header where we need it; if a function (or member function) can return a value
+ then a declaration of that value's type should be available (by including the
+ necessary header). For example, <code>deal.II/dofs/dof_handler.h</code>
+ includes <code>deal.II/dofs/dof_accessor.h</code> so that one can write
+ something like <code>dof_handler.begin_active()->is_active()</code> without
+ explicitly including the header declaring the type of the object returned by
+ <code>begin_active()</code>.
+
<li> Each class has to have at least 200 pages of documentation ;-)</li>
</ol>