abstract class in c++
struct Abstract {
virtual void f() = 0; // pure virtual
}; // "Abstract" is abstract
struct Concrete : Abstract {
void f() override {} // non-pure virtual
virtual void g(); // non-pure virtual
}; // "Concrete" is non-abstract
struct Abstract2 : Concrete {
void g() override = 0; // pure virtual overrider
}; // "Abstract2" is abstract
int main()
{
// Abstract a; // Error: abstract class
Concrete b; // OK
Abstract& a = b; // OK to reference abstract base
a.f(); // virtual dispatch to Concrete::f()
// Abstract2 a2; // Error: abstract class (final overrider of g() is pure)
}