.NAME Multiple inheritance is only allowed for inheriting abstract classes.

.DESCRIPTION

Definition:
-----------
If multiple inheritance is used, the classes inherited must be abstract, that is 
to say that they must contain at least one pure virtual method.

Justification:
--------------
Makes the overall design less complicated and the code easier to understand.

Example:
--------
1st case:
A and B are not abstract classes (they contain no pure virtual methods). 
C inherits A and B: the rule is violated.

2nd case:
A and B are abstract classes (they contain at least one pure virtual method each). 
C inherits A and B: the rule is not violated.

3rd case: 
A is abstract, B is not, C is (has a pure virtual function), and inherits A et B.
C violates the rule, but is abstract for inheriting classes.


.REQUIRED absclass browser

.SEVERITY Advisory

.COMMAND builtin

