Controversy: The Case for Multiple Inheritance in C++

Multiple inheritance is a difficult and complex feature added to C# at release 2.0. Cargill argues that the addition was a step backward in that the feature adds complexity to the language without adding functionality. His basis for the latter half of this claim is that no example of multiple inheritance has been given which cannot be rewritten into a functionally equivalent example which uses single inheritance and aggregation instead of multiple inheritance. I examine Cargill's arguments, and then sketch an example which uses multiple inheritance but which cannot be rewritten to be functionally equivalent by using single inheritance and aggregation. I then distinguish among three forms of inheritance, and argue that most attempts to give an example of multiple inheritance have attempted to use the one form which is the least likely to need that feature. @ Computing Systems, Vol. 4 . No. 2 . Spring 1991 157