a simple implementation of tuple via lambda.

LambdaTuple.hpp

#include <iostream>
using namespace std;

template <typename Storage>
struct LambdaTuple
{
	explicit constexpr LambdaTuple(Storage&& aStorage)
		: m_storage(move(aStorage))
	{
	}

	size_t Length() const 
	{
		return m_storage([](auto... args) { return sizeof...(args); });
	}

	template <typename UnaryFunc, typename... Args>
	decltype(auto) ApplyAfter(UnaryFunc&& aFunc, Args&&... inArgs) const 
	{
		return m_storage([=](auto... args) { return (aFunc)(inArgs..., args...); });
	}
	
	template <typename UnaryFunc, typename... Args>
	decltype(auto) ApplyBefore(UnaryFunc&& aFunc, Args&&... inArgs) const
	{
		return m_storage([=](auto... args) { return (aFunc)(args..., inArgs...); });
	}

	template <typename UnaryFunc>
	decltype(auto) Apply(UnaryFunc&& aFunc) const 
	{
		return m_storage([=](auto... args) { return (aFunc)(args...); });
	}

	Storage m_storage;
};

template <typename... Args>
decltype(auto) MakeLambdaTuple(Args&&... inArgs)
{
	auto storage = [=](auto functor) -> decltype(auto) { return functor(inArgs...); };
	return LambdaTuple<decltype(storage)>{move(storage)};
}

static bool test_func(bool, int, const char*, float)
{
	return true;
}

int main() 
{
	auto tuple = MakeLambdaTuple(1, "4", 3.f);
	bool ret = tuple.ApplyAfter(&test_func, true);
	return 0;
}