#include <iostream>
#include <functional>

template <typename> class curry;

template <typename _Res>
class curry< _Res() >
{
public:
    typedef std::function< _Res() > _Fun;
    typedef _Res _Ret;

private:
    _Fun _fun;

public:
    explicit curry (_Fun fun)
        : _fun(fun) { }

    operator _Ret ()
    { return _fun(); }
};

template <typename>
class decurry;

template <typename _Res, typename _Arg, typename... _Args>
class curry< _Res(_Arg, _Args...) >
{
public:
    typedef std::function< _Res(_Arg, _Args...) > _Fun;
    typedef curry< _Res(_Args...) > _Ret;

private:
    class apply
    {
    private:
        _Fun _fun;
        _Arg _arg;

    public:
        apply (_Fun fun, _Arg arg)
            : _fun(fun), _arg(arg) { }

        _Res operator() (_Args... args)
        { return _fun(_arg, args...); }
    };

private:
    _Fun _fun;

public:
    explicit curry (_Fun fun)
        : _fun(fun) { }

    _Ret operator() (_Arg arg)
    { return _Ret(apply(_fun, arg)); }


    friend class decurry< curry<_Res(_Arg, _Args...)> >;
};

template <typename>
class decurry;

template <typename _Res, typename... _Args>
class decurry< curry<_Res(_Args...)> > {
public:
    typedef curry<_Res(_Args...)> _Curried;
    typedef typename curry<_Res(_Args...)>::_Fun _Raw;

    decurry(_Curried fn): _fn(fn) {}

    _Res operator() (_Args... rest) {
        return _fn._fun(rest...);
    }
private:
    _Curried _fn;
};

template <typename _Res, typename _Res2, typename... _Args2, typename... _Args>
class curry< _Res(_Res2(_Args2...), _Args...) >
{
public:
    typedef curry< _Res2(_Args2...) > _Arg;
    typedef std::function< _Res2(_Args2...) > _RawFun;
    typedef std::function< _Res(_RawFun, _Args...) > _Fun;
    typedef curry< _Res(_Args...) > _Ret;

private:
    class apply
    {
    private:
        _Fun _fun;
        _RawFun _arg;

    public:
        apply (_Fun fun, _RawFun arg)
            : _fun(fun), _arg(arg) { }

        _Res operator() (_Args... args)
        { return _fun(_arg, args...); }
    };

private:
    _Fun _fun;

public:
    explicit curry (_Fun fun)
        : _fun(fun) { }

    _Ret operator() (_Arg arg)
    { return _Ret(apply(_fun, decurry<_Arg>(arg))); }
};

int test(std::function<int(int,int)> f, int x)
{ return f(3, 4) * x; }

int main ()
{
    auto func_xy = curry<int(int(int,int),int)>(test);
    auto plus_xy = curry<int(int,int)>(std::plus<int>());
    auto func_px = func_xy(plus_xy);
    auto func_p5 = func_px(5);
    std::cout << func_p5 << std::endl;

    return 0;
}