CRTP 多级 inheritance 用另一个模板参数实例化中间 class

Question

Given a multi level inheritance CRTP class structure like so, where the intermediate class B has another template parameter T, how should I instantiate an object of B?

template<class Derived, class T>
struct A {
    void print(T t) { static_cast<Derived*>(this)->print(t); }
};

template<template <typename> class Derived, class T>
struct B : public A<Derived<T>, T> {
    void print(T t) { cout << t << " B!\n"; }
};

template<class T>
struct C : public B<C, T> {
    void print(T t) { cout << t << " C!\n"; }
};

int main() {
    C<int> c;
    c.print(5);

    // how do I instantiate a B?
}

Answer 1

Here is an example of how you could do this.

template <typename T>
struct ForB { };

B<ForB, int> b;
b.print(5);

A link to try it out. http://cpp.sh/2v5tu

B itself is a template that takes in another template to instantiate. Here I created a dummy struct to demonstrate this. But this should work with any other templates as well.