[Pierre-Marie Baty]

IMO this is not an inheritance problem because your classes are inheritated fine from each other, but I think the problem comes that you can't assimilate a child class to its parent when trying to pass an instance of it as a parameter to the Sort() function. You'd better write overloaded versions of Sort() that would feature the parameter types you want and let the compiler link against the right one.

Other than that I don't know what a "Sort ((Sortable **) table, 20)" would give...

I'm not a big C++ guy anyway.