gistfile1.cpp

/*

clang++-3.6 -DVARIADIC_WRAPPER -O3 -Wall -Wpedantic -std=c++11 variadic.cpp
./a.out
objdump  -j .rodata -j .text -d -S a.out > a.txt

clang++-3.6 -O3 -Wall -Wpedantic -std=c++11 variadic.cpp
./a.out
objdump  -j .rodata -j .text -d -S a.out > b.txt

meld a.txt b.txt


g++ -DVARIADIC_WRAPPER -O3 -Wall -Wpedantic -std=c++11 variadic.cpp
./a.out
objdump  -j .rodata -j .text -d -S a.out > a.txt
g++ -O3 -Wall -Wpedantic -std=c++11 variadic.cpp
./a.out
objdump  -j .rodata -j .text -d -S a.out > b.txt

meld a.txt b.txt

*/

#include <tuple>
#include <iostream>
#include <functional>

//#define VARIADIC_WRAPPER 1

#ifdef VARIADIC_WRAPPER

__attribute__((noinline)) void foo(int x, int y) {
    std::cout << "A" << x << ":" << y << std::endl;
}

template<int ...>
struct seq {};

template<int N, int ...S>
struct gens : gens<N-1, N-1, S...> {};

template<int ...S>
struct gens<0, S...>{
    typedef seq<S...> type;
};

template <typename ...Args>
struct State {
    using Type = std::tuple<Args...>;

    State(void (*func)(Args...))
        : func(func) {}

    void (*func)(Args...);
    Type params;

    void operator()(Args... _param) {
        auto _params = std::make_tuple(_param...);
        if (_params != params) {
            params = _params;
            call(typename gens<sizeof...(Args)>::type());
        }
    }

    template<int ...S>
    void call(seq<S...>) {
        func(std::get<S>(params) ...);
    }
};

int main(void) {
    State<int,int> state(foo);
    state(1,2);
    state(1,2);
    state(2,2);
}

#else

__attribute__((noinline)) void baz(int x, int y) {
    std::cout << "B" << x << ":" << y << std::endl;
}

template <typename T>
class State {
public:
    void init(const typename T::Type& _default) {
        T::set(_default);
        m_current = _default;
    }

    inline void operator()(const typename T::Type& _value) {
        if (m_current != _value) {
            m_current = _value;
            T::set(m_current);
        }
    }

private:
    typename T::Type m_current;
};

struct Test {
    struct Type {
        int x; int y;

        bool operator!=(const Type& _other) { return  x != _other.x || y != _other.y;}
    };
    inline static void set(const Type& _type) {
        baz(_type.x, _type.y);
    }

};


int main(void) {
    State<Test> state;
    state({1,2});
    state({1,2});
    state({2,2});
}


#endif