GammaLib

Here a list of container classes that are not derived from GObjectContainer:

• GEbounds: The reason being that this class holds pairs of objects (lower and upper energies)
• GGti: The reason being that this class holds pairs of objects (lower and upper energies)

While trying to implement the interface for GPars I stumbled over this problem:

In GObjectContainer, the append method is defined using

virtual void append(const GBase& object) = 0;

while in GPars I want to have

virtual void append(const GPar& par);

This does not compile! One way out would be using

virtual void append(const GBase& par);

in the GPars class, but then the base object has to be typecasted.

For a discussion about this, read http://stackoverflow.com/questions/6004501/c-inheritance-with-pure-virtual-functions.

The advice ranges from “Do not do this” to “Use typecasting”.

As the GObjectContainer is just a interface definition, I’m reluctant of introducing typecasting just to satisfy the interface. Better not define the interface for these methods, which would concern append, insert and extend.

But if the interface is not fully defined, what is then the point for having an interface class?

One may argue that there is still some need for the generic container class methods that do not depend on the object type. Thus, we may decide to implement only a generic container class interface class GContainer:

class GContainer : public GBase {
public:
    virtual ~GContainer(void) {}
    virtual int size(void) const = 0;
    virtual bool isempty(void) const = 0;
    virtual void pop(const int& index) = 0;
    virtual void reserve(const int& num) = 0;
};