Standard C++ supports templates’ template arguments. For instance, a mail server class can store incoming messages in a vector of vector(s) of bytes:

 	vector< vector > vmessages;

Please note that the space between the left two angular brackets is mandatory. Otherwise, a >> sequence is parsed as the right shift operator. The same is true, of course, for a << sequence, so a typedef can be used to improve readability both for the compiler and the human reader:

 	typedef  vector msg;	vector vmessages;