I have a question about the best (and correct) approach for
defining namespace members.  The draft standard says that members
of a namespace can be defined within that namespace.  Since
namespaces can be spread over multiple files, it appears to be
possible to declare a member in a header file and define it in a
source code file, similar to the following:

 // in file f.h
 namespace N {  void f(int);  }

 // in file f.cpp
 namespace N {  void f(int n)  { ... }  }

However, several textbooks (Martin, Eckel, ...) seem to imply
that a member of a namespace can be defined at "file level"
using explicit qualification notation as follows:

 // in file f.cpp
 void N::f(int n)  { ... }