Question

How do I define func outside of the class declaration, below class A{...};?

template<typename T>
class A
{
    template<typename Q>
    class B
    {
        static void func(const A<T>& a){} // How do I define this function outside of the class declaration?
    };
};

Answer 1

With a double template:

template<typename T>
template<typename Q>
void A<T>::B<Q>::func(const A<T>& a)
{
}