layersExample.cpp

#include <iostream>

#define CRTP_SELF() \
    Self& self() { return *static_cast< Self* >( this ); } \
    const Self& self() const { return *static_cast< const Self* >( this ); }


template< template < typename > typename... Features >
struct Base: public Features< Base < Features... > >... {};

template < typename Self >
struct FeatureA {
    CRTP_SELF();

    void testA() {
        std::cout << "testA invoked\n";
    }

    void invokeBFromA() {
        std::cout << "Trying to invoke testB\n";
        self().testB();
    }
};

template < typename Self >
struct FeatureB {
    CRTP_SELF();

    void testB() {
        std::cout << "testB invoked\n";
    }

    void invokeAFromB() {
        std::cout << "Trying to invoke testA\n";
        self().testA();
    }
};

using MyType = Base< FeatureA, FeatureB >;

int main() {
    MyType x;

    x.invokeAFromB();
    x.invokeBFromA();
}