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How do you declare an interface in C++?
This is a general question about C++. As you know, there is no clear distinction between interface and abstract class in C++ unlike Java and C#. When would it be more preferrable to use an interface instead of an abstract class in C++? Could you give some examples?
An abstract class would be used when some common implementation was required. An interface would be if you just want to specify a contract that parts of the program have to conform too. By implementing an interface you are guaranteeing that you will implement certain methods. By extending an abstract class you are inheriting some of it's implementation. Therefore an interface is just an abstract class with no methods implemented (all are pure virtual).