Scatter hierarchy

gistfile1.cpp

// *************** behavior_scatter_hierarchy.h ***************

template <class T, class U>
struct TypeList
{
    using Head = T;
    using Tail = U;
};

struct NullType
{
};

template<typename T1> using TYPELIST_1 = TypeList<T1, NullType>;
template<typename T1, typename T2> using TYPELIST_2 = TypeList<T1, TYPELIST_1<T2>>;
template<typename T1, typename T2, typename T3> using TYPELIST_3 = TypeList<T1, TYPELIST_2<T2, T3>>;

template <class TList, template <typename M> typename B>
class ActorBehaviorScatterHierarchy;

template <class T1, class T2, template <typename M> typename B>
class ActorBehaviorScatterHierarchy<TypeList<T1, T2>, B>
    : public ActorBehaviorScatterHierarchy<T1, B>
    , public ActorBehaviorScatterHierarchy<T2, B>
{
public:
    using TList = TypeList<T1, T2>;
    using LeftBase = ActorBehaviorScatterHierarchy<T1, B>;
    using RightBase = ActorBehaviorScatterHierarchy<T2, B>;
};

template <typename AtomicType, template <typename M> typename B>
class ActorBehaviorScatterHierarchy: public B<AtomicType>
{
    using LeftBase = B<AtomicType>;
};

template <template <typename M> typename B>
class ActorBehaviorScatterHierarchy<NullType, B>
{
};

template <typename Msg>
struct Behavior
{
    Msg message_;
};

// *************** static_actor_test.cpp ***************

#include "behavior_scatter_hierarchy.h"

#include <iostream>

struct Message1
{
    uint32_t x = 5;
};

struct Message2
{
    float f = 0.123;
};

struct Message3
{
    std::string s = "hello!";
};


int main(void)
{
    using MyActorBehaviorHierarchy = ActorBehaviorScatterHierarchy<TYPELIST_3<Message1, Message2, Message3>, Behavior>;

    MyActorBehaviorHierarchy a;

    std::cout << static_cast<Behavior<Message1>>(a).message_.x << std::endl;
    std::cout << static_cast<Behavior<Message2>>(a).message_.f << std::endl;
    std::cout << static_cast<Behavior<Message3>>(a).message_.s << std::endl;
};