The classic is a pure virtual destructor: class abstract { public: virtual ~abstract() = 0; }; abstract::~abstract() {} You make it pure because there’s nothing else to make so, and you want the class to be abstract, but you have to provide an implementation nevertheless, because the derived classes’ destructors call yours explicitly. Yeah, I … Read more
Your problem is called slicing and you should check this question: Learning C++: polymorphism and slicing You should declare this list as a list of pointers to As: list<A*> listOfAs; and then insert these aB and aC pointers to it instead of creating copies of objects they are pointing to. The way you insert elements … Read more
Just went through this link virtual table and _vptr It says that the workflow will be like .. base_ptr->base_vptr—-> to check the access of virtual function in base class. base_ptr->derived_vptr->virtual_function()—> to call/invoke the virtual function. Hence the derived class virtual function is called.. Hope you find it helpful.
Because the type of a polymorphic object in C++ is, basically, determined from the pointer to its vtable, which is the table of virtual functions. The vtable is, however, only created if there’s at least one virtual method. Why? Because in C++, you never get what you didn’t explicitly ask for. They call it “you … Read more
It’s possible in GCC, but the way it’s documented in C++ language extensions section suggests there’s no portable way to do it. You can do two things: If you control the class, create a non-virtual function and a virtual wrapper for it and when you know you don’t need virtual dispatch, just take address of … Read more
Short Answer: No. Long Answer: It is not the base class or the number of ancestors a class has in its hierarchy that affects it speed. The only thing is the cost of a method call. A non virtual method call has a cost (but can be inlined) A virtual method call has a slightly … Read more
The most important part of Robert Crovella’s comment is: The objects simply need to be created on the device. So keeping that in mind, I was dealing with situation where I had an abstract class Function and then some implementations of it encapsulating different function and its evaluation. This is the simplified version of my … Read more
You just don’t want to do that, don’t even start. OO sure has its merits, but “classic examples” like your C++ one are almost always contrived structures designed to hammer the paradigm into undergraduate students’ brains so they won’t start complaining about how stupid the languages are they’re supposed to use†. The idea seems basically … Read more
You can’t check for override of virtual function portably. You need to bring the knowledge to the Solver, preferably via type as opposed to run-time flag. One (type-based) way is to check for presence or absence of a interface, via dynamic_cast. A probably better way is to provide overloads of solve function, in your case … Read more
Sure, and you don’t even have to define a method in the base class. In Python methods are better than virtual – they’re completely dynamic, as the typing in Python is duck typing. class Dog: def say(self): print “hau” class Cat: def say(self): print “meow” pet = Dog() pet.say() # prints “hau” another_pet = Cat() … Read more