Restrict C++ Template Parameter to Subclass

Question

How can I force a template parameter T to be a subclass of a specific class Baseclass? Something like this:

template 

        

Answer 1

To execute less useless code at runtime you can look at: http://www.stroustrup.com/bs_faq2.html#constraints which provides some classes that perform the compile time test efficiently, and produce nicer error messages.

In particular:

template struct Derived_from {
        static void constraints(T* p) { B* pb = p; }
        Derived_from() { void(*p)(T*) = constraints; }
};

template void function() {
    Derived_from();
}