+// Define an associative container that maps a name with a class and a
+// description. All classes must be derived from a same base class.
+//
+// We can then use the name to create an object of the associated
+// class, and to retrieve a pointer to this object.
+//
+// Furthermore, it is possible to iterate over the elements to get
+// their name and their description.
+
+// I am too lazy to comment the code, which should be obvious...
+